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Study on mechanical properties and energy evolution of Jinping deep buried marble
LOU Chendi, ZHANG Zhaopeng, WU Shiyong, ZHOU Jifang, PENG Yuan, AI Ting, LIU Yang, ZHANG Ru, REN Li
 doi: 10.12170/20210524002
[Abstract](31) [FullText HTML](13) [PDF 1845KB](1)
Abstract:
Compared with shallow rock mass, the occurrence environment of deep rock mass is more complex, which leads to the great difference between theri mechanical properties. The maximum buried depth of the tunnel in Jinping II hydropower station is more than 2 500 m, and the maximum ground stress of diversion tunnel is 70 MPa. It is of great theoretical value and practical significance to study the mechanical properties of hard rock under high stress conditions. Therefore, a series of static mechanical tests, including uniaxial and triaxial compression tests, were carried out systematically on Jinping marble from 2 400 m depth by MTS815 rock mechanics test system of Sichuan University. The test results show that the uniaxial compressive strength of Jinping marble is 180.43 MPa. With the increase of confining pressure, the marble shows the mechanical characteristics of “brittle-ductile-plastic” transformation, and 32.0 MPa is a demarcation point. At the same time, there are similar growth trends between the crack initiation stress, crack damage stress and crack peak stress, and the decreasing trend of the brittleness index is gradually flattened. Under low confining pressure, the elastic energy is dominant before the peak, while under high confining pressure, the dissipative energy increases more significantly, and the difference between pre-peak and post-peak elastic energy decreases, showing more obvious plastic characteristics. The research results provide a theoretical basis for accurately describing the mechanical behavior of deep rock and ensuring the stability of deep engineering.
Stability evaluation and cracking research of steep loess slope under continuous rainfall
WANG Lei, LI Rongjian, LIU Junding, YANG Zhengwu, SHI Jinfeng
 doi: 10.12170/20211022003
[Abstract](13) [FullText HTML](5) [PDF 3660KB](2)
Abstract:
Slope instability caused by continuous rainfall is one of the common geological disasters of loess slope. In order to study the influence of continuous rainfall on the seepage field, deformation field and stability of steep loess slope, the isolation slot technology with lateral seepage isolation and longitudinal drag reduction was used to treat the rainfall boundary on both sides of slope. On this basis, the field continuous rainfall (6 days) test was carried out, along with numerical simulation analysis. The cracking failure process and characteristics were described, and the water content and pore water pressure response were analyzed. The influence was also discussed of the cracking on the stability of steep slope. The results show that the isolation boundary leads to transverse through crack almost on the top of the slope, which eliminates the boundary constraint effect of the soil outside the local rainfall range substantially. The slope cracking has great influence on the distribution of water content and pore water pressure in the later stage of rainfall, which causes the center of maximum water content and pore water pressure to move down with the crack as vertical symmetry axis gradually, and the total water infiltration depth is 1.3 times that of the rainfall period 4 days after rainfall. The safety factor is reduced by 58% due to continuous rainfall of the slope, while the safety factor increases by 9% after 4 days of rainfall. The slope cracking caused the upper part of the steep loess slope to collapse easily. The research results provide a reference for the prevention and control of rainfall disaster of slope in loess area.
Urban waterlogging risk assessment of 7.20 heavy rainfall in Kaifeng City
FENG Feng, YU Qianhua, LUO Fusheng, HUO Jichao, FENG Yuehua, JIN Xiaoying, LIU Cui
 doi: 10.12170/20210824002
[Abstract](39) [FullText HTML](18) [PDF 11498KB](2)
Abstract:
On July 20, 2021, the heavy rain in Henan Province attracted wide attention due to its heavy rainfall intensity, long duration and frequent floods. The heavy rain caused serious water logging and waterlogging in Zhengzhou, Kaifeng and other cities. Aiming at the problem of urban waterlogging risk assessment, the data of 12 automatic monitoring stations were screened, and a semi-structural index system consisting of two dimensions of short-term risk and long-term risk and nine influencing factors was constructed. In the input layer, information entropy weight vector is adopted, and in the criterion layer, three weighting methods are adopted: entropy weight vector, equal weight vector and decision preference weight vector, which constitute the improved risk fuzzy evaluation model. Waterlogging risk was assessed at five levels (very high, high, medium, low, and very low) for 12 sites. The results show that: in the short-term risk assessment, site 5 is very high risk, and site 10 is medium risk. In the long-term risk assessment, site 6 is high risk, and site 8 is very low risk. In the final evaluation of the target layer, the three methods all showed that the risk of No. 5 and No. 2 sites was very high, and the risk of No. 7 and No. 8 sites was low. Compared with the actual situation of waterlogging in Kaifeng City, the evaluation system and improved model are considered to have strong applicability. Accurate evaluation results of short-term risk, long-term risk and comprehensive risk can be provided for urban waterlogging risk, providing reliable data support for urban drainage pipe network improvement and waterlogging water point prevention and control. It provides a basis for making emergency disaster reduction plan and countermeasures to deal with waterlogging caused by rainstorm.
Spatiotemporal changes of extreme precipitation in the Pearl River Delta region
ZOU Xianju, SONG Xiaomeng, LIU Cuishan
 doi: 10.12170/20210714002
[Abstract](17) [FullText HTML](11) [PDF 5156KB](3)
Abstract:
It is of great significance to study the evolution of regional extreme precipitation for scientific response to regional water resources utilization and disaster prevention and reduction under the changing environment. In this work, six extreme precipitation indices defined by the ETCCDI (Expert Team on Climate Change Detection Monitoring and Indices) are selected to analyze the temporal and spatial evolution of extreme precipitation in the Pearl River Delta region by using the linear trend, Kriging interpolation and cross wavelet methods. Besides, the correlation between atmospheric circulation anomalies and extreme precipitation is identified. The results show that: (1) Except for CWD, all the indices have increased by various magnitudes during the period of 1961—2017. It indicates that extreme precipitation is increasing in the Pearl River Delta, but the change is not significant. (2) The stations with increasing trends are mainly located in the central and northern parts of the region, and the stations with a significant change are in the northern part of the Pearl River Estuary and the northern part of the region. (3) The spatial distribution of each index is similar but slightly different for various climate states (1961—1990, 1971—2000, 1981—2010, 1990—2017, also called State 1, State 2, State 3, and State 4)(无中文摘要与加粗部分对应, 中英文摘要含义应一致? ? ? ) . The spatial patterns of trends for the four states are significantly different, with the change magnitudes increased from State 1 to State 4. (4) The CDD index is significantly affected by IOD, while the ENSO significantly influences the other indices.
Evaluation and calibration of Sentinel-3A SRAL Level 2 product over Poyang Lake
HUANG Dui, WANG Wenzhong, LIU Jiufu, ZHANG Jianyun, CUI Wei, WEI Li, MIN Min
 doi: 10.12170/20210616005
[Abstract](34) [FullText HTML](30) [PDF 2282KB](5)
Abstract:
The Sentinel-3 Satellite Synthetic Aperture Radar Altimeter (SRAL) data is one of the emerging data sources for monitoring water level. Combined with the water body information of Poyang Lake extracted by Landsat-8 and Sentinel-2 optical remote images, the Sentinel-3A SRAL satellite measurements near Xingzi hydrological Station were extracted. According to the principle of satellite altimetry considering geophysical corrections, an outlier elimination rule and automatic calculation of each date satellite water level process was proposed, and combined measured water level to evaluate and calibrate the Sentinel-3A radar altimeter retrieved water level. Results showed that the effective rate of Sentinel-3A satellite data in Poyang Lake is 64%, valid data cover March to September. The Pearson correlation coefficient of satellite retrieved water level and measured is greater than 0.99, and there was a significant correlation at the level of 0.001. The Pearson correlation coefficient between satellite water level change and measured water level change is 1, the average deviation is −0.175 m and STDEVA is 0.084. For ascending and descending orbit, the value of the statistics in descending orbit is better than those in ascending orbit. For high-water and low-water seasons, the value of the statistics in the low-water season are better than those in the high-water season, and the statistical index in the low-water season is the smallest: the average deviation is −0.082 m, RMSE is 0.107 m. The average absolute deviation of the calibration water level using the average deviation between the measured data and satellite altimeter water level in 2016-2017, 2016-2018, 2016-2018 as the calibration parameter both are 0.073 m, R-value is 1. The water level calibration results based on different calibration parameters have little difference. The study proved the effectiveness of the method of satellite altimetry data calculation and lake water level calibration, which is conducive to hydrology, climate change research, and monitoring of flood control and drought resistance.
Sensitivity analysis of water resources supply and demand balance to precipitation changes in Beisanhe River Basin
LIU Tao, WANG Gaoxu, WU Yongxiang, WU Wei, TIAN Xueying, ZHANG Nina
 doi: 10.12170/20210926003
[Abstract](8) [FullText HTML](9) [PDF 2302KB](1)
Abstract:
Analyzing the sensitivity of water supply and demand balance in different regions to changes in precipitation, combined with the spatial distribution of cloud water resources and precipitation efficiency, is helpful to determine the location of normalized artificial precipitation enhancement, and is of great significance to the realization of the coordinated use of air and land water resources. This paper takes the Beisanhe River Basin as the research area, analyzes the response of the study area’s incoming water demand to precipitation changes based on the Xin’anjiang Model and Penman-Montes formula, and discusses the sensitivity of the water supply and demand balance of different computing units to precipitation changes. The results show that: Affected by changes in precipitation, the rate of increase in annual water production in the basin is greater than in dry years and extreme dry years, and the water demand for farmland irrigation is roughly linear. Under the natural rainfall scenario, the resource water shortage in the basin is 3.546 billion cubic meters (P= 50%), 4.317 billion billion cubic meters (P=75%) and 4.630 billion cubic meters (P=95%), and the peak of water shortage appeared in May, July and August, respectively. The sensitivity of each unit’s water shortage to changes in precipitation is mainly dominated by changes in water production, and shows a gradual decrease in space from north to south. When the average annual precipitation increases by 20%, the relative decrease rate in the northern region will reach 150% or more, the central region will be between 30% and 50%, and the southern region will decrease less than 15%.
Longitudinal analysis model of shield tunnel considering mechanical characteristics of ring joints
YAO Jiachen, YANG Jianxi, ZENG Dong, LI Tongchun
 doi: 10.12170/20211208003
[Abstract](22) [FullText HTML](26) [PDF 2284KB](2)
Abstract:
The ring joints of shield tunnels have obvious nonlinear mechanical characteristics, and it is difficult to analyze the longitudinal deformation of tunnels reasonably to simulate the response of the stress and deformation. In order to solve this problem, this paper proposes a simple and practical model for the analysis of joints between rings, that is, the contact surface element that can transmit pressure but not tension is used to simulate the ring-to-ring contact, and the beam element based on the embedded beam generalized displacement method is used to simulate bolts. The nonlinear contact state at the joint between the rings and the axial stiffness and shear stiffness of the joint bolts are considered, and it is suitable for all kinds of bolt shapes between the rings (straight bolts, bent bolts or oblique bolts). A calculation example is used to compare the calculation results of the finite element and the theoretical analysis model to verify the accuracy of the model. The model is applied to the longitudinal deformation analysis of shield tunnels crossing the fault fracture zone in an actual project. The results show that the water conveyance shield tunnel is stable in homogeneous bedrock, and the deformation of the lining ring joints in the fault fracture zone. The bolt stress increases significantly, but is within the design control range. The model can provide a certain reference for engineering safety construction and operation.
Prototype observation of hydraulic characteristics of filling and emptying system of Guigang Second Line Ship Lock
LUO Huijing, YAN Xiujun, LI Zhonghua
 doi: 10.12170/20220107001
[Abstract](5) [FullText HTML](8) [PDF 1682KB](0)
Abstract:
Guigang second line ship lock is an important navigation hub in the main shipping line of Xijiang River. As a giant ship lock with medium and high water head, it adopts a simple decentralized filling and emptying system layout of gate wall Gallery side branch outlet and double open ditch energy dissipation, which is rare in China. In order to verify the reasonable layout of the system, the proper operation mode of the gate valve and ensure the safe and efficient operation of the ship lock, the prototype observation test of the hydraulic characteristics of the ship lock filling and emptying system was carried out. The observation results show that the hydraulic characteristics of the lock chamber and the berthing conditions of the ship basically meet the code and design requirements, and the flow patterns at the inlet and outlet of the lock and in the lock chamber are good; Under the current ship lock head and recommended gate valve operation mode, the superelevation and drop in the lock chamber at the end of water conveyance exceed the specification requirements. After putting forward improvement measures for the operation mode of the lock valve, the problem has been improved; There is a deviation in the discharge coefficient between the prototype and the model of the ship lock, and the deviation value shall not exceed 6%; The operation of double track lock under different working sequences has little influence on each other.
Seismic fragility of offshore wind turbine considering scour depth
LI Fen, WANG Yizhi, HONG Zibo, HU Dan
 doi: 10.12170/20210630001
[Abstract](12) [FullText HTML](6) [PDF 1143KB](2)
Abstract:
The geological conditions in the eastern coastal areas of China are complex, and the saturated soft clay around the offshore wind turbine foundation may be affected by the local erosion and dynamic water pressure conditions around the pile under the cyclic action of earthquake and waves. In this paper, the nonlinear dynamic model of offshore wind turbine considering the earthquake hydraulic pressure and scour effects was established. A total of 34 earthquake records were selected based on the site target response spectrum. Based on the multi-band analysis method, the seismic vulnerability curves of offshore wind turbine under various working conditions were obtained, the influence of earthquake hydraulic dynamic pressure and scour depth on the seismic vulnerability of offshore wind turbines were discussed further. The results indicated that under the seismic fortification intensity, the scour depth has a significant impact on the normal operation of offshore wind turbine under seismic load, but has marginal effect on the permanent failure of wind turbine. By comparison, the hydrodynamic pressure has little effect on the seismic vulnerability under different limit states. The vulnerability analysis of offshore wind turbine can serve as a guidance for the seismic design of offshore wind turbine.
Analysis of runoff and sediment characteristics of Datong Station based on Copula function
HUANG Yuming, JIAO Jian, DOU Xiping, GUO Haijun, DING Lei
 doi: 10.12170/20210408003
[Abstract](92) [FullText HTML](33) [PDF 2118KB](7)
Abstract:
The Yangtze River estuary has been strongly influenced by human activities, and the consistency of its runoff-sediment sequence has been damaged. Based on the monthly runoff and sediment data from 1965 to 2019 at Datong Station, a sliding window algorithm based on Copula is applied to investigate the variation characteristics of runoff and sediment in the Yangtze estuary and the consistency of its abundance-depletion, and the uncertainty of the marginal distribution selection for the joint runoff-sediment distribution model is also analyzed. The results show that: (1) The runoff-sediment combination at Datong Station shows a decreasing trend from 1965 to 2019 due to human activities, and changes abruptly in 1979 and 2000. The optimal function models for the runoff-sediment series in 1965-1979 and 1980—2000 are Clayton, while 2001—2019 is best modeled by Frank; (2) the synchronous frequencies of the runoff-sediment series in the three periods are 84.52%, 84.40% and 83.20% respectively, which are much greater than the asynchronous frequencies of abundance-depletion, revealing the strong consistency of the incoming runoff-sediment in the upper reaches of the Yangtze River; (3) the 95% confidence interval of the PE3-PE3 marginal distribution combination is smaller than that of the PE3-GPD combination, indicating that the PE3-PE3 combination would reduce the uncertainty of function selection. By exploring the joint variation characteristics of incoming runoff and sediment at Datong station, this study provides a reference for water resources management and river regulation in the Yangtze estuary.
Ecosystem health assessment and its spatial and temporal change characteristics of the Yangtze River Economic Belt
YU Zhiqiang, CAO Hao, WANG Zhengyong, CHENG Weishuai
 doi: 10.12170/20200519001
[Abstract](61) [FullText HTML](48) [PDF 2539KB](6)
Abstract:
The health of ecosystem in the Yangtze River Economic Belt (YREB) is an important key factor to the sustainable development of China’s economy and society. Based on the framework of Vigor-Organization-Resilience Contribution, an ecosystem health assessment model was built for the YREB, and the ecosystem health for each country in 2000 and 2015 was analyzed. The result showed that: (1) The ecosystem health was higher in the upstream and south of the Yangtze River (e.g. Yunnan province), while lower in the downstream and north of the Yangtze River (e.g. Anhui province and Jiangsu province); (2) An overall increase of ecosystem health index was detected from 2000 to 2015. However, in some local areas, especially coastal regions of Yangtze River Delta Area, the ecosystem health index decreased; (3) In 2015, the ecosystem health of the Yangtze River Economic Belt was dominated by four factors, the four-factor dominant area accounted for 41.2% of the total area, and most of them were transformed from the primary three-factor dominant area in 2000. In general, the ecosystem health of the YREB recovered during the study period, but declined in the areas with intensified human activities.
Reunderstanding on rain and flood resources utilization
HU Qingfang, WANG Yintang, DENG Pengxin, LI Lingjie, WANG Leizhi, YUN Zhaode
 doi: 10.12170/20220216004
[Abstract](1) [FullText HTML](1) [PDF 887KB](0)
Abstract:
Rain and flood are valuable natural resources. Rain and flood resources utilization both have a long history and are vital water resources utilization ways. In recent years, practical technologies of rain and flood resources utilization have advanced greatly, but there are still remarkable misunderstandings on their basic conceptions. Extensive use of some nonstandard terms brought confusion to scientific research and practice. Therefore, in light of the relevant history and reality and according to the basic theory of hydrology, a discussion on rain and flood resources utilization is drawn and preunderstanding was obtained in this paper. The natural resources and water resources properties of rain and flood were clarified. Then, the basic connotation and definition of rain and flood resources utilization were summarized. Also, the relationship between rain resources utilization and flood resources utilization was analyzed. In addition, the normalization of some technical terms including so called rainwater reuse and flood reuse were clarified. This paper is helpful to eliminate the misunderstandings about rain and flood resources utilization and consolidate the theoretical basis of the safe and efficient utilization of rain and flood resources. Our understanding create good prerequirements for the scientific evaluation, planning and technology innovation of rain and flood resources utilization.
Discriminating piping process in sandy gravels based on Reynolds number
WANG Yu, GU Yanchang, WANG Shijun, DUAN Xiangbao
 doi: 10.12170/20211014001
[Abstract](32) [FullText HTML](21) [PDF 1707KB](0)
Abstract:
Piping is one of the main reasons of dike and dam break in defective reservoir. Traditional seepage theories focus on piping mechanism, developing process and controlling measures, yet seldom research on quantitative discrimination and nonlinear characteristics of piping overall process. Groups of laboratory tests of piping process in different grading sandy gravels were conducted, and the judging method of piping overall process was proposed by the analysis of fluid regime changes based on the Reynolds number, which shows that fines content and uniformity are main influence factors of piping failure. The whole process of piping in sandy gravels can be quantitatively divided into four stages, that is, incubation (Re<0.85), formation (0.85≤Re≤5.00), evolution (5<Re≤50) and destruction (Re>50). During incubation and formation stages, removable fine particles are started up and adjusted, and the relationship between hydraulic gradient and seepage velocity is linear. Viscous drag force plays an important role, and seepage flow conforms to the Darcy’s law. However, during evolution and destruction stages, seepage pathway is gradually formed and developed, and removable fine particles run off rapidly. Meanwhile, the seepage velocity changes increasingly, and the relationship between hydraulic gradient and seepage velocity is nonlinear, which shows the inertial force plays a leading role. Laminar flow gradually transfers into turbulent flow, which can be described by a quadratic equation. The research findings would provide the base for piping scientific forecast and emergency disposal.
Application of extraneous water quantity diagnosis method in pre-diagnosis of sewer network system
FENG Hanghua, CHEN Haitao, SHI Xiang, GUO Shuai
 doi: 10.12170/20210518001
[Abstract](65) [FullText HTML](32) [PDF 2215KB](9)
Abstract:
In order to achieve the goal of full coverage, full collection and full treatment of sewer system, many cities have carried out investigation and renovation projects of drainage network. The project of sewage quality and efficiency improvement represented by "Yangtze River Protection" pointed out that the pre-diagnosis of pipe network should be carried out before the comprehensive investigation and renovation work. In order to solve this problem, a pre-diagnosis method based on extraneous water quantity analysis is proposed. This paper introduces the purpose, significance, diagnosis content and technical route of the pre-diagnosis method, and comprehensively uses the water balance method, chemical mass balanced method and the method based on flow measurement to diagnose the sewage network of a southern city in the "Yangtze River Protection" project. The diagnosis results show that: the overall proportion of extraneous water in the sewage system of a southern city is about 16%; but the extraneous water in some catchments is more than 50% in dry days; the rainwater inflow in rainy days is serious, and more than half of the catchments are more than 30%. Through the pre-diagnosis of the drainage network, it has a certain significance to guide the investigation and renovation of the pipe network.
Analysis of the spatial - temporal evolution characteristics of water resources - economic society - ecological environment coupling and coordination in Gansu Province
ZHANG Tianzi, WANG Xiaojun, QI Guangping, KANG Yanxia, YIN Minhua, MA Yanlin, JIA Qiong, ZHANG Xiangning
 doi: 10.12170/20220406001
[Abstract](14) [FullText HTML](6) [PDF 1595KB](1)
Abstract:
The complex coupling relationship exists between water resources, economic society and ecological environment, and promoting the coupling and coordination of the three is an important prerequisite for achieving sustainable regional development. Based on the coupling coordination degree model, this paper measures the coupling coordination degree of water resources-economic society-ecological environment system in 14 cities and states of Gansu Province from 2010 to 2019, and analyzes the evolution characteristics of the coupling coordination degree by combining with the evolution model of center of gravity. The results show that (1) the overall water resources-economic society-ecological environment comprehensive evaluation index of Gansu Province showed a slight upward trend during 2010-2019, and its spatial distribution was consistent with the distribution pattern of water resources endowment, economic and social development and ecological environment management in each city and state. ; (2) the coupling coordination degree of the three systems in Gansu Province is between [0.52,0.54], which belonged to the basic coordination type, the spatial dimension of the coupling coordination type of each city (state) was either stable or improving; (3) the trajectory of the center of gravity of the coupling coordination degree from 2010 to 2019 was mainly in Lanzhou City, with an average annual distance of 7.19 km. A differentiated strategy should be adopted to promote the evolution of water resources-economic society-ecological environment towards advanced coupling coordination.
Intelligent acquisition method of piezometric pipe group water depth based on image recognition technology
FAN Gufei, GAO Ang, WANG Fangfang, LUO Jie
 doi: 10.12170/20210830001
[Abstract](7) [FullText HTML](2) [PDF 1219KB](2)
Abstract:
In order to accurately and quickly obtain the water pressure of different parts of the water-passing structure in the hydraulic model test, a method and system for the intelligent acquisition of the water depth of the piezometric pipe group based on image recognition technology has been proposed and designed. The system adopts a non-contact (shot from a side) image acquisition method which could shoot real-time moving images of water surface buoys in a large number of pressure measuring tubes (reflecting the changing process of water depth), and then import the image data into the computer; the software recognition system adopts grayscale, binary values and opening operations to preprocess the image in preparation. When pretreatment work finished, findContours would be used to obtain the centroid coordinates of the water surface buoys of each piezometer tube, which would be converted into actual water level data through calibration coefficients, and finally the time series of the synchronous changes of the water depth in each piezometer tube would be obtained. Compared with the traditional manual measurement method, the verification result of hydraulic model test shows that the data error obtained by this method is no more than ±1.5% compared with the traditional manual measurement method, but the acquisition method is faster, the data is richer, and the accuracy is higher.
Experimental study on shear failure characteristics of weak expansive oxidized soil under atmospheric conditions
NAN Yalin, GUO Hong, CHEN Dongliang, CHEN Wentao
 doi: 10.12170/20210624001
[Abstract](37) [FullText HTML](16) [PDF 1477KB](9)
Abstract:
Under atmospheric environment conditions, the natural oxidation of expansive soil may occur. The chemical composition, mineral composition and particle structure of clay particles changed. In order to study the effect of atmospheric oxidation on the physical properties of Liulin weak expansive soil, the chemical components of undisturbed soil and oxidized soil clay were compared by XRF component detection and laboratory geotechnical test methods. The shear deformation and failure modes of undisturbed soil and oxidized soil samples were studied under different confining pressures. The hardening characteristics of soil samples under compression and shear failure modes are analyzed by the principal stress-strain constitutive relation. The results show that the key factor was the change of the internal friction angle for the increase of the shear strength index. Under the experimental loading conditions, the failure modes of undisturbed soil samples and oxidized soil samples are different, and various failure modes may occur, such as buckling compression, hardening compression, compression and shear mixing, or shear slip. For soil materials with softening properties, the hardening coefficient can be used to describe the nonlinear characteristics of the sample transition from compression hardening to compression shear mixing and shear softening failure mode. This paper can provide a theoretical reference for the study of the oxidation effect of expansive soil and the analysis of its engineering stability.
Analysis of arch aqueduct on pile foundation based on generalized displacement method for Built-in beam
HU Rongjin, PI Jiajun, PAN Shiyang, HUANG Yongtao, LIU Xiaoqing
 doi: 10.12170/20210929002
[Abstract](4) [FullText HTML](2) [PDF 2250KB](1)
Abstract:
The arch aqueduct on pile foundation is formed by beam-column and block structure. The structure should be discretized to beam element and isoparametric element respectively in finite element method analysis. But there is a problem of how to overcome the coordination of corner displacement between beam elements and isoparametric elements. Based on the generalized displacement formula of the beam element node as the master node, the generalized displacement expression between the rotational displacement of the beam element node and the displacement of the embedded isoparametric element node is established. By setting different grid sizes and element stiffness, the applicability of master-slave or slave-master generalized displacement mode between beam element and isoparametric element for structural analysis of arch aqueduct on pile foundation is studied and discussed. The method is also applied to the analysis of an arch aqueduct project. The research results can be popularized to all the interaction problems between beam, slab, column and block structure.
Advance on autogenous shrinkage and its regulation of modern concrete
LI Jinghao, HE Xiaobo, HU Shaowei, JIANG Jianhua, ZHAO Haitao
 doi: 10.12170/20220111001
[Abstract](10) [FullText HTML](4) [PDF 3126KB](1)
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Concrete is the most widely-used structure materials, and modern concrete is produced with a low water to binder ratio and high binder materials content to obtain high performances, leading to a significant increase in autogenous shrinkage (AS), and thus triggering a large tensile stress under restraint and further a serious early-age cracking, which deteriorates the concrete durability, shortens the service life and causes an incalculable loss, especially in hydraulic mass concrete and thin-walled concrete structures. This paper reviewed the literatures on the latest achievements and progress home and abroad for AS and its regulation in recent years, summarizing and comparatively analyzing the latest achievements and progress upon methods and devices for AS “time-zero” and deformation measurement, AS prediction models and AS regulation techniques, pointing out the flaws in current research and giving the further research direction on some key problems, and setting a reference for practical engineering and further AS study.
Numerical simulation on deformation and failure of blocky jointed rock mass considering the effect of confining pressure
ZHAN Yide, WANG Faxiang, SHE Tianyu, SHEN Jiayi, LÜ qing
 doi: 10.12170/20211220002
[Abstract](7) [FullText HTML](5) [PDF 1117KB](2)
Abstract:
The determination of deformation modulus of jointed rock mass is of great importance for the design and stability analysis of deep rock mass engineering. Therefore, it is of great engineering significance to study the effect of confining pressure on deformation characteristics and failure modes of jointed rock masses. Combining discrete element numerical simulations and laboratory testing data, triaxial numerical simulations on deformation and failure of blocky jointed rock masses with two pre-existing joints under different confining pressures were carried out. The main conclusions are as follows: (1) The deformation modulus of blocky jointed rock masses increase with the increase of confining pressure. When the confining pressure is more than 4 MPa, the change of deformation modulus tends to be gentle; (2) The failure modes of blocky jointed rock mass can be divided into two types: the sliding failure along the existing joints and the shear failure across the whole rock mass. With the increase of confining pressure, the failure mode of the blocky jointed rock mass model develops from sliding failure with joints to shear failure in intact rock. (3) For 1+2, 2+3, 3+5 and 5+7 blocky jointed rock mass models, the confining pressures at which the failure mode changes are 0.5, 1.0, 4.0 and 4.0 MPa, respectively.
Analysis of seepage and dam slope stability for anti-seepage transformation of Juershang silt dam
CHEN Binxin, NIE Xingshan, TIAN Chun
 doi: 10.12170/20210509001
[Abstract](7) [FullText HTML](9) [PDF 1725KB](0)
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In order to improve the utilization rate of surface water in small watersheds and solve the problem of irrigation water in mountainous areas, the paper carries out the technical research of anti-seepage modification of Juershang silt dam in Pianguan County, Shanxi Province. Aiming at the upstream slope of the silt dam, this paper puts forward five reconstruction schemes including original soil thickening, clay inclined wall and composite geomembrane. The seepage and slope stability of the original dam and various modification schemes are numerically simulated considering the coupling effects of seepage field and stress field. The results show that the original dam is greatly affected by the seepage water and cannot store water safely; only the original soil thickening of the upstream slope of dam cannot make the dam meet the requirements for seepage prevention; laying a clay inclined wall or geomembrane anti-seepage body on the upstream slope can effectively reduce the infiltration line, reduce the seepage flow and improve the stability of the downstream slope of dam; the geomembrane scheme has better safety and feasibility than other schemes, and can be given priority if conditions permit. The research results have certain guiding significance for the anti-seepage transformation projects of similar silt dams.
A preliminary study on the conceptual connotation and characteristics and criterion of optimization of river and lake systems interconnection
LÜ Lianghua, ZHANG Haibin, CHEN Xiaoyan, GENG Leihua, SONG Cuiping
 doi: 10.12170/20210622001
[Abstract](42) [FullText HTML](21) [PDF 712KB](7)
Abstract:
In response to the need to build a national modern water network with the functions of integrated management of water resources, water environment, water ecology, and water disasters in the new era, how to optimize the connection of rivers and lakes to minimize the negative effects and maximize the comprehensive positive effects is an urgent problem in the field of river and lake systems interconnection. Combining with the multi-functional requirements of river and lake systems interconnection in the new era, the conceptual connotation and characteristics were proposed, and preliminarily analyzed and discussed. On this basis, combined with the new requirements of the water security situation in China for the river and lake systems interconnection, the criteria that should be followed in the optimization of river and lake systems interconnection were preliminarily discussed from the aspects of the “sixteen-character” water conservancy thinking, “12-character” principle, “three before three” principle, equal emphasis on engineering and management, and following the laws of nature and history. It is expected to provide a reference for the further research on the optimization of river and lake systems interconnection.
Calculation analysis on the discharge capacity of Piano Key weir and relative influencing factors
LI Yanfu, HAN Changhai, LI Zixiang, HAN Kang, YU Kaiwen
 doi: 10.12170/20211111001
[Abstract](12) [FullText HTML](7) [PDF 1214KB](1)
Abstract:
In recent years, the problem of insufficient discharge capacity of existing hydraulic engineering has become more and more serious due to the frequent occurrence of extreme flood. The Piano Key weir has a high-efficiency discharge capacity when the water head on the weir is proper low. The calculation analysis of its discharge capacity has great practical value. The discharge capacity is related to main structural parameters of the Piano-Key-weir and the water head on the weir. In this study, the influencing structural parameters of discharge capacity of the Piano Key weir was summarized, and the optimal values were suggested. Different overflow pattern formed on Piano Key weir under different hydraulic conditions. Low water head behavior happened when the water head flowing on the Piano Key weir was low. Based on the existing experimental data, the hydraulic condition and structural parameters when low water head behavior happening was statistically analyzed. A comparative analysis among existing discharge capacity estimation formulas of Piano Key weir was performed. Then, combining with the existing experimental data, a new discharge coefficient formula including L, W, B, P, Wi/Wo and Bo/Bi was proposed based on least squares method and genetic algorithm, and the predicted results is in good agreement with the experimental data of a large number of different Piano Key weir types with the average error less than 6%. Among the estimation formulas, Machiels’ formulas is suitable for the detail analysis of the discharge of Piano Key weir. The new formula in this study and Guo Xinlei’s formula are both simple to calculate and can be used to estimate the overall discharge capacity of Piano Key weir, and the suitable formula can be selected according to the practical requirement.
Study on hydraulic characteristics simulation and optimal layout of open wide single chute spillway
ZHANG Wenjiao, LIU Lei, WU Caiping, WU Teng, LUO Liqun, HU Nengming
 doi: 10.12170/20210609001
[Abstract](65) [FullText HTML](39) [PDF 1640KB](17)
Abstract:
Compared with the general spillway, the open spillway with wide single chute is prone to complicated flow pattern and poor aeration effect. Taking the Baleh Hydropower Project in Malaysia as an example, this paper uses the VOF method and the RNG k-ε two-equation turbulence model to carry out a three-dimensional numerical simulation of the spillway flow field. The calculation and analysis of the distribution law of the hydraulic characteristics of the spillway under different working conditions, such as flow pattern, velocity, and pressure along the way. At the same time, a 1∶50 physical model test was carried out. After comparative analysis, the model test results were basically consistent with the numerical simulation results, which verified the accuracy and feasibility of the numerical simulation of the hydraulic characteristics of the spillway with an open wide single chute. Then the turbulence model was used to calculate and analyze the optimized layout of the spillway aeration sill in detail. The results show that: after the 1# aeration sill is raised by 20 cm, the length of the aeration cavity behind the sill increases from 11.03 m to 19.84 m, and the energy dissipation rate increases approximately doubled; after 3# aeration sill moved up 15 m along the steep slope of the chute, the impact position of the tipping water tongue moved upward, reducing the impact on the flow pattern of the tipping nose sill section. The research results have a certain reference effect on the optimization design of similar projects.
Numerical simulation of split grouting of heterogeneous clay with different permeability coefficient
SHEN Shizhao, TU Xiaobing, LEI Jinsheng, ZHOU Ke, LIU Jinxin, TANG Yazhou
 doi: 10.12170/20210826002
[Abstract](7) [FullText HTML](3) [PDF 5291KB](0)
Abstract:
Considering the heterogeneity and low permeability of the clay materials, the fracture grouting reinforcement characteristics of the clay are analyzed in view of the disease treatment of soft clay stratum in underground engineering. Based on Weibull distribution function theory, a heterogeneous clay formation model was constructed, and the clay was simulated by splitting grouting. Based on the results of grouting simulation, the influence of different uniformity and permeability coefficient on the grouting effect of clay splitting is analyzed. The results show that the difficulty of splitting grouting increases with the increase of the uniformity of soil mass, and the crack produced by splitting of soil mass with higher uniformity is relatively single and the distribution range of crack is smaller. The crack width is larger and the influence range is wider when the soil is less homogeneous. The length and growth amplitude of slurry vein expansion decrease with the increase of soil permeability coefficient. The width of slurry vein in the soil with large permeability coefficient is larger than that in the soil with low permeability coefficient. The length of slurry vein in the soil with small permeability coefficient is always larger, and the farther the slurry vein is from the grouting hole, the smaller the width. The research has important guiding significance for the engineering application of fracture grouting in soft clay stratum.
A review of long-term expansion prediction model of concrete suffering alkali-aggregate reaction
WANG Jimin, BAI Yin, DING Jiantong, MAO Xuegong, CAI Yuebo
 doi: 10.12170/20210805001
[Abstract](33) [FullText HTML](18) [PDF 2244KB](4)
Abstract:
Alkali-aggregate reaction is called the "cancer" of concrete and is one of the important factors affecting the durability of concrete. For the concrete structure with active aggregate, how to predict the long-term deformation of concrete caused by alkali-aggregate reaction and reasonably evaluate the overall safety of the structure is a problem of close concern to the project. In this paper, the research progress of long term deformation prediction models for alkali-aggregate reaction of concrete is reviewed. The existing models are classified into 5 categories: mathematical modeling of macroscopic expansion, phenomenological model of macroscopical deformation of structures, models based on aggregate expansion, models based on ASR gel and models based on material migration. The advantages, disadvantages and application scope of various models are analyzed. It is proposed that the prediction model of ASR long-term expansion needs to consider the effect of alkali ion diffusion into the aggregate, SiO2 dissolution and the composition of ASR gel, and the reaction ring model or gel pocket model should be selected according to the petrographic analysis.
Analysis of typical flood precipitation and water level elements in Taihu Lake Basin
HU Qingfang, ZHU Rongjin, WANG Yintang, LI Lingjie, LI Xiting
 doi: 10.12170/20210914001
[Abstract](7) [FullText HTML](6) [PDF 1540KB](0)
Abstract:
In order to deepen the understanding of flood movement and urban hydrological laws in the basin, in this study, we comprehensively compared the 2020 flood with three historical floods in 2016, 1999 and 1991 in the Taihu Lake Basin, and analyzed the similarities and differences of the precipitation and water level elements corresponding to the four basin floods. It was found that in terms of the distribution of precipitation, the flood-causing precipitation processes in 1991, 1999 and 2016 were relatively concentrated but with intermittent periods, while the flood-causing precipitation in 2020 could be regarded as a continuous precipitation process, with a large cumulative rainfall but a more uniform time history distribution. In terms of the spatial distribution of precipitation, 1991 and 2016 were "northern type", the flood-causing precipitation in the northern water conservancy district was significantly higher than other subregions, and the 1999 was "southern type", southern flood-precipitation was higher than other sections. However, in 2020, it was "watershed type", with relatively small gaps in flood-causing precipitation among water conservancy districts. Affected by the precipitation process, the water level of Lake Taihu during the flood periods of 1991, 1999, and 2016 had a certain fall or a stable period, but the water level of Lake Taihu during the 2020 flood period showed a continuous increase process. During the 2020 flood period, the highest water level at the representative station in the southern Zhexi obviously exceeded that in 1991 and 2016, but the water level situation in the northern Huxi and Wuchengxiyu were less severe than in 1991, 1999 and 2016. In general, the scale and intensity of floods in the Taihu Lake Basin in 2020 were lower than in 1999 and other years, and its disaster losses were also relatively smaller. However, it still had important reference value for the design of rainstorms, flood calculations and dispatches in the basin and region.
A numerical study on the development length of secondary waves in an intermediate navigation channel
ZHENG Feidong, LI Yun, WANG Xiaogang
 doi: 10.12170/20210921001
[Abstract](10) [FullText HTML](4) [PDF 1563KB](1)
Abstract:
The intermediate channel between two decentralized cascade locks is an impounded navigation channel. The filling and emptying of lock chambers during lock operation leads to oscillations of the free-surface elevation in the channel, which can increase the degree of difficulty encountered maneuvering a ship and even produce ship accident in some instances. In previous works, most of the research effort has been devoted to the propagation of long waves in intermediate navigation channels. In contrast, the study of secondary waves in the channels has received less attention so far. In the present study the development of secondary waves under the layout of decentralized cascade locks for the new waterway in Three Gorges project was fully considered. A coupled model based on the basic equations of ship locking and Boussinesq equations was first established. Subsequently, the development length of secondary waves and its response to related hydraulic parameters were investigated. The results demonstrated that during lock emptying, the development length of secondary waves was solely related to the maximum discharge per unit width in a form of power function. In contrast, the relationship between the development length and the maximum discharge per unit width was not unique but depended on the initial head of lock chambers during lock filling. Based on the numerical results, two empirical formulas were proposed to predict development length under different locking operations. The present finding can provide theoretical guidance and technical support for the hydraulic design and operation of decentralized cascade locks.
Energy dissipation characteristics of the open ditch located in a large-scale ship lock chamber with an extreme high water head
CHEN Ming, CHEN Yanji, MIAO Jiankang, HUANG Haijin
 doi: 10.12170/20210805008
[Abstract](13) [FullText HTML](9) [PDF 2319KB](0)
Abstract:
In order to study the energy dissipation characteristics of open ditch combined with the side ports located in an in-chamber culvert designed for a large-scale lock chamber with an extreme high water head, in case of the water head 60 m and the useful dimension of the lock chamber 280 m×40 m (length×width), the three-dimensional turbulent numerical simulation method was used to analyze the parameters such as velocity, turbulent energy distribution, remaining specific energy and flow velocity distribution uniformity, present the energy dissipation characteristics of the single open ditch with double-layer side ports and the double open ditches with single-layer side ports, Moreover, the corresponding energy dissipation results between them were compared. The results showed that for the case of the single open ditch with the double-layer side ports, when the ratio of vertical spacing d between ports to square root of side ports area D, d/D, increasing from 2.29 to 5.71, the energy dissipation results become better firstly and then worse. When d/D reached 3.43, the corresponding energy dissipation results could be the best. In addition, the widening type of the double open ditches (the ratio of one open ditch width b to square root of side ports area D, b/D=2.71) had better energy dissipation effect than that of the type of the single open ditch with the double-layer side ports. The research results could provide technical support for the design of energy dissipators in similar ship locks.
Experiment study on the strength and microstructure of bentonite-lime improved loess
GAO Mengna, WANG Xu, LI Jiandong, ZHANG Yanjie, JIANG Daijun
 doi: 10.12170/20210818003
[Abstract](17) [FullText HTML](12) [PDF 1592KB](1)
Abstract:
Loess has poor engineering performance and must be treated before it can be used as roadbed filler. In order to improve the bearing capacity of the loess subgrade, better solve the engineering disease problem of the loess subgrade. Bentonite and lime are added to the loess roadbed filler, and the unconfined compressive strength test and nuclear magnetic resonance test of different combinations of bentonite-lime-loess are carried out. From the perspective of soil strength and pore structure, each content is studied. Bentonite-lime improves the strength and pore structure of loess roadbed fillers. The test results show that bentonite can effectively fill the pores of loess, lime can make the dispersed particles in the soil form a whole, and increase the unconfined compressive strength of the soil by 4.01 times; the unconfined compressive strength of the improved loess increases with the maintenance Compared with plain loess, the porosity of modified loess decreases, and the proportion of large pores decreases significantly. Scanning through a microscopic electron microscope found that the soil particles were connected as a whole, and the large pores between the particles were basically filled. Therefore, the improvement effect of bentonite and lime on loess filler is more significant.
Diagnosis of sluice crack working behavior based on velocity and acceleration criteria
XU Shimei, HUANG Yaoying, XU Xiaofeng, YIN Xiaohui, HAO Dan, CHEN Fei
 doi: 10.12170/20210816001
[Abstract](4) [FullText HTML](16) [PDF 2637KB](0)
Abstract:
The fracture measured data of comprehensively reflect the influence of complex factors on macroscopic crack behavior of hydraulic concrete structure. The aging component is an important basis for evaluating crack working behavior. In this research, the crack working behavior is diagnosed based on the velocity and acceleration criteria. Combined with the actual situation of the discharge sluice of Wangfuzhou Water Conservancy Project. Firstly, the typical crack location of hydraulic concrete structure is selected to install crack meter group, and then the measured data of cracks experiencing adverse load conditions are monitored and obtained. Then, the crack statistical model reflecting the nonlinear effect of temperature is established, and the aging component is separated and obtained. Finally, the velocity and acceleration criteria are used to diagnose the aging component. The application analysis of measured fracture data shows that considering the effect of nonlinear temperature crack statistical model fitting effect is good, although Wangfuzhou discharge sluice access door of water conservancy projects, some cracks which point aging component of convergence performance, but all tend to be closed, diagnostic Wangfuzhou discharge sluice cracks in a stable state at present. This method can reflect the time-varying law of cracks simply and reliably, and provide a reference for the diagnosis of working behavior of cracks in hydraulic concrete structures.
Investigation of torsional penetrometer for simulation of track-soft clay interaction
HUANG Weijian, LIAO Chencong, LIU Shiao, YE Guanlin
 doi: 10.12170/20210728006
[Abstract](14) [FullText HTML](3) [PDF 2128KB](0)
Abstract:
Underwater track vehicle will compress and shear the soil as it walks over a soft clay seabed. The compression reflects the depth of penetration and the strength of clay, and the shearing decides the traction that clay could provide. Traditional bevameter technique comprises two separate sets of tests, one is a plate penetration test and the other is a shear test, to simulate this process, ignoring the interaction effect between compression and shearing. In this paper, a new form and work method of torsional penetrometer is proposed, unifying the compression and shearing of seabed into the sequential penetration and torsion of the penetrometer. The validity and feasibility of the torsional penetrometer concept are verified by comparisons with the previous indoor model tests. In view of the normal solidified soft clay common in the deep sea, by means of finite element method connected with Modified Cam-clay Model, the sensitivity analysis of grouser height and pitch are conducted based on the torsional penetrometer. Finally, and the influence of track parameters on the mobilized strength of soft clay seabed is explored. The results show that the grouser height and pitch have a significant effect on the strength of soft clay, and appropriately increasing the tooth height and reducing the pitch will help to give full play to the strength of soft clay.
Study on the interactive relationship between water resources and industrial upgrading of the Yellow River Basin
LIU Jianhua, TANG Qi
 doi: 10.12170/20210906002
[Abstract](8) [FullText HTML](7) [PDF 1009KB](2)
Abstract:
The comprehensive evaluation index system of water resources and industrial upgrading of the Yellow River Basin was constructed. Based on the indices from index calculation, a spatio-temporal analysis was performed. Using PVAR model, with Granger causality test, impulse response and variance decomposition, the interaction between water resources and industrial upgrading of the eight provinces in the Yellow River Basin over the years 2010 to 2019 was empirically analyzed. According to the analysis results, the corresponding countermeasures and suggestions were proposed. The results indicated that: ① It was difficult for the eight provinces in the Yellow River Basin to promote the industrial structure adjustment by optimizing the water resources utilization pattern. It was necessary to find new driving forces of development, enhance the added value of the industrial chain, and establish a modern industrial system; ② The optimization of water resources utilization of the eight provinces in the Yellow River Basin had a promoting effect on enhancing the industrial environmental friendliness. Great efforts should be made to promote the sustainability of water resources utilization in the Yellow River Basin, and ecological compensation mechanism should be established; ③ The improvement of industrial environmental friendliness of the eight provinces in the Yellow River Basin played a positive role in improving the condition of water resources. Vigorous efforts should be made to develop renewable energy, promote the green level of industry, and restore the status of water resources.
Study on the simulation and comparison of clean water diversion scheme and field test in Changzhou main urban area
MU Shousheng, LIU Yang, WU Jingxiu, FAN Ziwu, LIU Guoqing, XIE Chen
 doi: 10.12170/20210416002
[Abstract](34) [FullText HTML](47) [PDF 3320KB](3)
Abstract:
In order to improve the water environment of the main urban area of Changzhou City, through the combination of numerical simulation calculation and field test, the research on the scheme of improving the water environment of smooth flowing water was carried out. Using high-quality and abundant water from the Yangtze River as the water diversion source, the Weicun water conservancy project and the Zaogang water conservancy project were used to divert water. Five groups of simulation schemes were set for the new project of Daxi project of Dayun River and the dispatching combination with four movable weir projects. Through the hydrodynamic mathematical model, the flow distribution of the river in the urban area under each scheme was simulated. Based on the field test, the effect of the recommended scheme was demonstrated. The results show that the recommended scheme has formed a smooth flow pattern of three-level water level difference, accurate water level regulation and reasonable flow distribution, and the water environment of the river network has improved significantly. At the same time, most of the water quality indicators are still in a good state within 16 days after the end of water diversion, but the water quality of some rivers has rebounded significantly. It is an effective way to improve the water environment of plain river network cities to carry out hydrodynamic regulation through the mathematical model. However, it is necessary to strengthen daily monitoring, reasonably determine the living water cycle according to the water quality changes, and carry out pollution source analysis for some abnormal water quality points, so as to ensure the long-term treatment of river network water environment.
Comparative study on mechanical properties of concrete for a hydraulic complex project
FAN Xiangqian, LIU Jueding, GE Fei, TANG Lei, HAN Haotian
 doi: 10.12170/20211115001
[Abstract](13) [FullText HTML](9) [PDF 2205KB](2)
Abstract:
In order to discuss the mechanical properties and fracture characteristics of dam concrete, three-point bending test of concrete beam was carried out based on two different concrete mix ratios (named C0.48 and C0.43 respectively according to different moisture content) provided by a hydraulic complex project and on-site coarse and fine aggregates. The relevant mechanical properties such as slump, compressive strength and splitting strength were determined, and the effects of different mixing ratios on fracture parameters such as fracture surface, cracking load and instability load, critical effective crack length and double K fracture toughness were analyzed. The test results show that, the collapse of C0.48 concrete is greater than that of C0.43 concrete. The compressive strength and splitting strength of C0.48 concrete are lower than that of C0.43 concrete. The coarse aggregate of C0.48 concrete fracture surface is not obvious as that of C0.43 concrete. The cracking load, destabilization load, critical effective crack length and fracture toughness of C0.43 concrete are higher than those of C0.48 concrete, which indicates that C0.43 concrete has high strength, good ductility and good toughness.
Ecological operation of Lijiang parallel reservoirs considering ecological flow requirement of fish
YANG Peisi, WANG Li, MO Kangle, CHEN Qiuwen, LI Ting, ZENG Chenjun, TANG Lei, ZHANG Hui
 doi: 10.12170/20210715002
[Abstract](15) [FullText HTML](7) [PDF 2281KB](3)
Abstract:
The joint operation of reservoirs brings huge economic and social benefits, and also has a lot of impacts on the river ecology. In order to improve the comprehensive benefits of power generation, navigation、 ecology and Qingshitan Reservoir storage of the joint operation of Lijiang parallel reservoirs , the multi-objective parallel reservoirs operation model considering ecological flow requirement of fish are developed. The model is optimized by Non-Dominated Sorted Genetic Algorithm-Ⅲ. The results show that (1) Compared with regular operation, parallel reservoirs optimal operation can ensure the benefit of power generation, and guarantee the benefit of navigation and ecology at the same time. (2) The constructed multi-objective parallel reservoir ecological operation model maintains the rate of ecological flow requirement above 47% in dry, normal and wet years. In particular, the ecological demand of fish during the winter, spawning and breeding periods is guaranteed. (3) The implementation of joint operation of the Lijiang parallel reservoirs can alleviate the pressure of water supply of Qingshitan Reservoir, and increase the reservoir storage in dry and wet years by 22.26×106 m3 and 24.55×106 m3 respectively. This study can provide reference for multi-objective ecological operation of parallel reservoirs
Study on volume changes and strength characteristics of expansive soil under complex boundary conditions
LI Yan, WANG Sihai, ZHU Rui
 doi: 10.12170/20210627001
[Abstract](53) [FullText HTML](28) [PDF 1934KB](5)
Abstract:
The soil in seasonally frozen soil regions is easy to be affected by the coupling environment, which is related to the canal operation. Taking the typical canals in Northern Xinjiang as background, the experimental study on the volume changes and strength of expansive soil under wet-dry (WD), freeze-thaw (FT) and coupled wet-dry-freeze-thaw (WDFT) cycles was carried out. The deformation and strength characteristics of expansive soil under the different boundary conditions and cycles are discussed. The results show that the volume changes of samples tend to be constant after four WD cycles. During the FT cycles, the volume change of samples decreases with the increasing FT cycles. In the coupled WDFT cycles, the volume changes of samples are affected by the combination of WD effect and FT effect. The saturation of approximately 70% may be the critical saturation for the occurrence of "frost shrinking and thaw expanding" and " frost expanding and thawing shrinking ". The WD process in the coupled WDFT cycles has a certain weakening effect on the volume changes of samples during the subsequent FT process in the coupled WDFT cycles. Meanwhile, the strength of samples decreases significantly under the coupled WDFT cycles. After 7 coupled WDFT cycles, the sample strength decreased by 46.9% ~ 59.1%. The attenuation degree of strength is related to saturation under WD cycles and FT cycles. The research results can provide a basis for the construction and maintenance of expansive soil canals in Northern Xinjiang.
Numerical study on thermal regimes beneath canal in permafrost zones with different geological conditions
HANG Hongwu, MU Yanhu, YU Hong, DING Zekun, CHEN Ling
 doi: 10.12170/20210108001
[Abstract](15) [FullText HTML](11) [PDF 1703KB](1)
Abstract:
In permafrost regions, construction and operation of hydraulic engineering will exert considerable thermal impact on underlying permafrost, and its degree will be different at locations with different permafrost geological conditions. Taking a canal in a high altitude permafrost zone as an example, a water-thermal coupled mathematical model for freeze-thaw soils was established in this paper. The water migration, ice-water phase change and nonlinear relationship between unfrozen water content and temperature in freezing soils were considered in the model. Using this model, the long-term evolution of the thermal conditions of permafrost subgrade under the canal in the context of climate warming was numerically investigated, and the influences of the mean annual ground temperature (MAGT) and ice content (iv) of the permafrost subgrade were considered. The results showed that, when the permafrost is ice-poor (iv < 10%), both the vertical and lateral thermal erosion of the canal are significant. After 50 years of the excavation, there is no permafrost under the mid-bottom and bank slope of the canal. When the MAGT is −0.5℃, the permafrost under the canal has degraded within about 10 m from the bank slope outward. While when the MAGTs are −1.0 or −1.5℃, there is still permafrost under the bank slope of the canal. With the increase in iv, the thermal inertia of permafrost increases significantly. When the iv increases from ice-poor to ice-rich (20% < iv ≤ 30%), there is still permafrost existing under the canal in 50th year after the excavation even when the MAGT is −0.5℃. However, a thawed layer shaped as a pot-bottom develops beneath the canal. Under the impacts of climate warming and water thermal erosion, the permafrost beneath the canal experiences significant downward degradation, or quick descend of the permafrost table. While only under the impacts of climate warming, the permafrost beneath the slope of canal and the natural ground surface experiences slow descend of the permafrost table and slight warming of the top permafrost layer.
Experimental study on mechanical properties and microscopic mechanism of expansive soil in a project in north Xinjiang
CUI Ziyan, ZHANG Lingkai
 doi: 10.12170/20211220006
[Abstract](28) [FullText HTML](18) [PDF 4398KB](2)
Abstract:
The first project of north Xinjiang water supply in expansive soil area, it has been multiple sliding failure phenomenon since running. Our primary aim is to explore the sliding failure mechanism, the indoor direct shear test, compression test, seepage test and electron microscope scanning test of soil are carried out separately, the results of mechanical properties soil are investigated and their affecting mechanism are discussed. The results are as follows: (1) The cohesion is decreases with the increase of water content. The internal friction angle decreases slowly when it is less than the optimal water content, and then decreases significantly. Due to dry density increasing, the cohesion increases significantly and the internal friction angle increases slower. (2) According to the analysis result, the stable void ratio decreases trend with increasing water content, and the compressibility of soil increases. With increasing dry density, the initial void ratio decreases, and the stable void ratio tends to be constant. With increasing consolidation pressure, the structure type of soil gradually evolves to turbulence and laminar flow structure from flocculation structure, the effect of particle aggregation is obvious, the number and size of pores decreases, and the compressibility of expansive soil decreases, all above are established based on result of scanning electron microscopy experimental test (SEM). (3) The permeability of expansive soil is strong under low consolidation pressure, and it is small under high pressure (200~1 600 kPa), with an order of 10−6~10−8. The permeability coefficient is positively correlated with the void ratio, which can be expressed in the form of power function. The results of scanning electron microscopy (SEM) show that the loose accumulation structure changes into a closely combined laminar flow structure with increasing consolidation pressure, and the area of pores decreases, which provides the conditions for the permeability coefficient decreases significantly.
Research on interpolation and transfer of co-integration and set pair analysis in rainfall data shortage areas
WANG Xiujie, QI Xiling, TENG Zhenmin, LI Dandan
 doi: 10.12170/20210721001
[Abstract](8) [FullText HTML](5) [PDF 1251KB](1)
Abstract:
In view of the shortage of rainfall data in small and medium watersheds and the difficulty of accurate flood forecasting, this paper proposes to use linear cointegration and set pair analysis (SPA) to interpolate and transfer the observational rainfall data under typhoon rain and non-typhoon rain. Reservoir conducts flood forecasting research. The results show that: (1) Based on the typhoon rain cointegration calculation results, it is found that there is a cointegration relationship between rainfall stations. The Nash coefficients of the cointegration simulation results and the measured rainfall are both above 0.85, and the correlation coefficient reaches 0.90. the main rain peak and the raining error are small. The calculation results are good and the integration theory can be used for data interpolation when rainfall. (2) The non-typhoon rain rainfall sequence is decomposed by supplementary ensemble empirical mode (CEEMD) and SPA, and the optimal plan for data migration is drawn up according to the comprehensive connection degree, which significantly improves the effectiveness and accuracy of the migration of rainfall data, and improve flood forecasting accuracy. The method proposed in this paper provides a new idea for the interpolation and transfer of rainfall data in other regions with both typhoon storm and non-typhoon storm.
Reduction of multi-point displacement monitoring data of reservoir bank slope based on spatio-temporal clustering mining
CHEN Bo, ZHAN Mingqiang, HUANG Zishen
 doi: 10.12170/20210728002
[Abstract](5) [FullText HTML](9) [PDF 1904KB](0)
Abstract:
The instability disaster of reservoir bank slope will cause huge losses to the benefit of the project and the safety of surrounding life and property, and the displacement monitoring data can directly characterize the safety status of reservoir bank slope. In view of the traditional deformation and displacement analysis, only a single monitoring point is considered, and the similarity and relevance of displacement between different monitoring points still need to be excavated. Based on the clustering method in the field of spatio-temporal data mining, considering the attribute characteristics and spatial characteristics of measuring points, K-means algorithm is used to measure the similarity between measuring points and realize the division of measuring points; based on the division of measuring points, the projection clustering algorithm optimized by genetic algorithm is used to map the high-dimensional data to the low-dimensional space. By extracting the characteristics of measuring point data, the purpose of screening the measuring points needing attention and compressing the data order is achieved. Combined with practical engineering data, it shows that the spatio-temporal clustering mining method is convenient and effective, and gradually reduces the monitoring data of slope displacement, which can be used for monitoring data mining of similar reservoirs.
Coupling analysis of hydraulic fracturing of crack in the heel of gravity dam
ZHENG Anxing, PAN Guoyong
 doi: 10.12170/20220110003
[Abstract](10) [FullText HTML](2) [PDF 1922KB](3)
Abstract:
The cracks in the heel of gravity dam usually bear the action of high water head during the operation of the dam, which is prone to hydraulic fracturing failure. In this paper, the crack hydraulic fracturing coupling numerical model of gravity dam under the framework of extended finite element method is established, and the crack propagation process of gravity dam heel under the coupling of hydraulic fracturing is simulated by extended finite element method. The calculation results show that the heel of the gravity dam initially gradually extends to the dam base, and the crack propagation direction is towards the downstream. The crack angle without hydraulic fracturing is larger than that under hydraulic fracturing, and the crack angle without hydraulic fracturing coupling is smaller than that under hydraulic fracturing coupling. Before the crack propagation in the heel of gravity dam, the water pressure in the crack is basically the same as the boundary water pressure. When the crack begins to expand, the water pressure in the crack will drop, and then the crack opening width will continue to increase, and the water pressure in the crack will become the boundary full head. Hydraulic fracturing of cracks leads to the increase of type I stress intensity factor at the crack tip and reduces the stability of cracks in gravity dam. The research results provide an important theoretical basis for the hydraulic fracturing prevention of cracks in the heel of gravity dam.
Comprehensive analysis for leakage cause of the entry and outlet sections of the water-conveyance crossing structures
HU Jiang, WANG Chunhong, MA Fuheng
 doi: 10.12170/20211022002
[Abstract](35) [FullText HTML](10) [PDF 2550KB](8)
Abstract:
Abstract . There is uncertainty for the cause of the abnormal seepage flow in the entry and outlet sections of the water-conveyance crossing structures. A comprehensive analysis method was proposed to explore the leakage cause in the outlet section of a cross-river aqueduct in a long-distance water transfer project in this paper. First, the operation management data such as patrol inspection and reinforcement measure were analyzed. A statistical model was constructed to quantitatively analyze the relationship between the seepage pressure in the transition section and the uplift pressure beneath the sluice chamber and the cannel water level, temperature, rainfall and other environmental variables. The main influencing factors of the seepage variables were preliminarily judged by the above-mentioned qualitative and quantitative analysis. Second, combined with the engineering geology and hydrogeological conditions, the leakage cause of the protective structure can be further judged through the analysis of the surface deformation monitoring data. Then the leakage entrance and leakage channel was revealed based on several geophysical detection methods such as flow field method, ground penetrating radar and high-density resistivity method. Finally, according to the comprehensive analysis, it is concluded that the leakage enters from the structural joints at the end of the transition section, and leaks out to the protective structure through the sand and gravel layer foundation of the transition section, the sluice chamber section and the connecting section. Considering the long-term operation of the water transfer project, it is difficult to stop water transfer for the aqueduct maintenance. Therefore, the anti-seepage reinforcement treatment plan namely adding a grouting curtain to block the seepage channel beneath the sluice chamber was proposed. The adopted comprehensive analysis method can provide a reference for the analysis and the treatment of similar engineering problems.
Study on energy and momentum correction coefficients in compound open-channel flows
ZENG Cheng, QIU Fei, DING Shaowei, ZHOU Jie, XU Jianbo, WANG Lingling, YIN Yuran
 doi: 10.12170/20210705002
[Abstract](35) [FullText HTML](15) [PDF 1492KB](5)
Abstract:
In compound open-channel, the energy and momentum correction coefficients have a direct impact on the accuracy of hydraulics calculation. The purpose of this study was to investigate the impacts of flow depth ratios and vegetation densitis on the distributions of energy and momentum correction coefficients in compound open-channel flows. Numerical simulations are performed with a three-dimensional model with the wall-modelled large eddy simulation (WMLES) method for five depth ratios conditions and three vegetation densities conditions. The results show that the correction coefficients of energy and momentum between the main channel and the floodplain are obviously different due to the non-unifomity of velocity distribution. The values are all greater than one. When the flow depth ratios increases, the velocity distribution of the compound section tends to be uniform.The range of the energy correction coefficient and momentum correction coefficient are 1.07~1.19 and 1.03~1.07, respectively. In addition, with the increase of vegetation density, the velocity difference between main channel and the floodplain increases, and the correction coefficients of energy and momentum of the section increase accordingly. The range of the energy correction coefficient and momentum correction coefficient are 1.09~1.59 and 1.04~1.21, respectively. Finally, through regression analysis, it is found that there is a linear relationship between energy correction coefficient and momentum correction coefficient, and this formula can predict the value of energy correction coefficient and momentum correction coefficient under a same condition.
Assessment of water resources vulnerability and identification of its contribution factors in typical dry year in Henan Province
WANG Liping, ZHANG Yiwen, ZHANG Jianyu, LIU Cuishan, WANG Guoqing
 doi: 10.12170/20211015001
[Abstract](25) [FullText HTML](12) [PDF 1771KB](4)
Abstract:
Water resource vulnerability is an important measurement of water security and the basis of regional sustainable development. Taking Henan Province and 18 cities as evaluation unit, the index system of water resource vulnerability evaluation was established by considering three subsystems of natural condition, social economy as well as water supply and consumption. Entropy Weight Method and Linear Weighting Method were used to calculate water resource vulnerability of typical dry year. The water resource subsystem index and vulnerability index were investigated from city, region to the entire province. The Contribution Model was applied to identify the principal contribution factors of water resources vulnerability in order to provide scientific basis for water resources management in Henan Province. The results show that the subsystem indexes range from water resources natural condition index, water resources supply and consumption index, to water resource socio-economic index. And there exist a certain difference in water resources subsystem index and vulnerability index at different levels of urban cities, regions, and province with the both indexes increasing from southwest to northeast. The water resources vulnerability for the entire Henan Province grades No. Ⅲ, is medium vulnerability. The contribution of the three sub-systems to water resource vulnerability for the main cities and the whole province follows a same rank order from natural condition, water supply and consumption condition, to social economic condition. The four indicators of the natural condition sub-system are principal contribution factors to water vulnerability. The per-mu chemical fertilizer conversion scalar in the socio-economic subsystem and the per-capita comprehensive water consumption and per-mu irrigation water consumption in the water-supply-consumption subsystem are also major contribution factors to water resources vulnerability. The three subsystems should take “multi-channel water supply, improving the capacity of water supply”, “rationally expanding cities and towns, optimizing population and economic structure, improving urban living and production level”, “improving water utilization efficiency, saving water” as the breakthrough points to achieve accurate “vulnerability reduction”, so as to guide the sustainable development of water resource.
Application and expectation of non-metallic navigation aids technology in marine environment
SUN Hongyao, LI Hongwei, LI Weiyun
 doi: 10.12170/20210910005
[Abstract](17) [FullText HTML](6) [PDF 1167KB](5)
Abstract:
The total cost of corrosion in China accounts for about 3.34% of GDP every year, so the research on advance anticorrosion materials and technologies has always been a hot spot. This paper summarizes the application status of domestic non-metallic material for aids to navigation (ATON) technology in marine environment, analyzes the cost and performance differences of each material for aids to navigation. The results show that reinforced concrete light beacons shall be gradually sifted out. Steel and FRP (Fiber Reinforced Plastic)-polyurea composites material and UHMWPE (Ultra High Molecular Wight Polyethylene) ATONs are still the main structural forms of light beacons. Steel buoys are still the main structural form of buoy by now. The application of UHMWPE buoys is gradually expanding, and the application scale of FRP buoys is shrinking. Finally this paper puts forward the development trend of non-metallic material for aids to navigation.The future development trend of ATON is that, improving the performance of non-metallic materials, optimizing the structure design of non-metallic material ATONs, increasing the research and development investment of non-metallic material ATONs, especially non-metallic material ATONs with light weight, high impact resistance property, low cost, anticorrosion, anti bio-foul and low water absorption rate, and formulating relevant technical specifications and standards in time.
Strength evolution model of hydraulic concrete subjected to salt freezing
GAN Lei, FENG Xianwei, SHEN Zhenzhong
 doi: 10.12170/20210725001
[Abstract](21) [FullText HTML](5) [PDF 1311KB](4)
Abstract:
The problem of strength deterioration of hydraulic concrete structures in salt lakes and saline soil areas in cold regions is outstanding. Based on the theory of isotropic continuous damage mechanics, the quantitative relationship between relative dynamic elastic modulus and relative compressive strength of concrete was presented. Next, a concrete strength evolution model under the synergistic action of freeze-thaw and sulfate erosion was proposed, and the model was verified.Finally, the model is applied to verification of Yindaruqin aqueduct over Zhuanglang River performance evaluation. The research results show that the model could well simulate the strength evolution law of concrete subjected to salt frost erosion, and through numerical simulation analysis, it is found that the numerical results of the aqueduct are consistent with the operating conditions. With the deterioration time increasing, the maximum compressive stress and displacement of the aqueduct body increase, while the maximum tensile stress decreases. Salt freezing will accelerate the deterioration rate of the aqueduct, and the aqueduct would be damaged after 59.1 years of operation. The research results can provide theoretical basis for performance evaluation and operation maintenance of hydraulic concrete eroded by salt freezing in cold and arid areas.
Review on diagnosis and monitornig methods of structural behavior of superhigh arch dams
ZHAO Erfeng, GU Chongshi
 doi: 10.12170/20211203005
[Abstract](20) [FullText HTML](9) [PDF 1017KB](12)
Abstract:
Several superhigh arch dams have been built or are under construction in China. These projects are often located in special service environments with high water head, high slope and complex geological conditions. Their technical indicators have broken through the applicable scope of current codes and previous engineering cognition, including design, construction, safety monitoring, etc. Compared with ordinary arch dams, the engineering complexity of superhigh arch dams increases sharply with the dam height, and the structural mechanical behavior has more unique characteristics, leading to stringent requirements of safety control during construction and operation. The key technologies of structural behavior diagnosis of superhigh arch dams have been explored systematically, such as engineering empirical evaluation parameters, geomechanical model tests, numerical simulation analysis. Furthermore, safety control technologies have been deeply investigated, including construction quality control, temperature control and crack prevention, monitoring feedback analysis. On the basis, hot issues of health diagnosis and safety control of superhigh arch dams during future long-term operation are expounded, which are mining methods of space-time evolution characteristics, real-time diagnosis model of operation risk probability, dynamic control model of structural safety, intelligent perception and early warning technology. The aforementioned research aspects are critical for improving the future intelligent construction and management of superhigh arch dams.
Recent earth-filled dam failure or danger accident of reservoirs in China and its enlightenment
ZHANG Shichen, LI Hongen
 doi: 10.12170/20211024002
[Abstract](30) [FullText HTML](24) [PDF 858KB](11)
Abstract:
Affected by extreme weather, dam failure and accidents have occurred in recent years, and some regularity trend is gradually clear. Some new phenomenon and new directions such as the excessive flood impact, earth-rock dam overtop but not collapse, emergency response mechanism and so on should set to be studied deeply. It is necessary to analyze and study the latest dam-break and escape cases. This paper summarizes experience and draws lessons from flood control standards, monitoring and early warning, emergency response and emergency treatment, studies and puts forward enlightenments in reservoir dam safety management and flood control, and further puts forward thoughts and suggestions on strengthening dam failure risk prevention and control. Conclusion: quick lowering water level is the key to deal with the excessive flood measures; earth dam can be done and not collapse; earth and rockfill dam structure design should give full consideration to the extreme working condition of strong rainfall; it is necessary to strengthen the flood control capacity for river cascade reservoirs; management facilities had a great influence on emergency response ability; lower management influence the flood control safety significantly.
Multi-scale regional definition and its application selection in the Yellow River Basin
ZUO Qiting, WU Qingsong, JIANG Long, ZHANG Wei
 doi: 10.12170/20210923001
[Abstract](21) [FullText HTML](10) [PDF 914KB](4)
Abstract:
The Yellow River Basin involves a vast area, complex and diverse issues, and the corresponding research content is relatively rich. There is a problem of inconsistency in the scope and partition of spatial research. Based on the Yellow River’s major national strategic objectives, tasks and different research needs, considering the relevance of the river basin and administrative regions in terms of resource utilization, economic development and ecological protection, the spatial research scope of the Yellow River Basin is defined as Yellow River basin, administrative regions that the Yellow River mainstream flows through, prefectural regions involved in the Yellow River basin, entire provincial regions that the Yellow River flows through, and other research scopes and divisions also are expounded. Then, four regional definition schemes are compared and analyzed from multiple aspects (i.e., spatial scope, research object and content, administrative management), and the relationship between different schemes is further clarified. According to the principles of pertinence and purpose, we systematically sort out the selection of different research content on the spatial scale, and solve the problem of under what circumstances a spatial scale can or should be selected. The research results can provide a unified standard and reference basis for subsequent studies in the Yellow River Basin.
Study on super-standard flood situation in Dongting Lake area
YANG Binghui, SHI Yong, LUAN Zhenyu, JIN Qiu
 doi: 10.12170/20211029002
[Abstract](14) [FullText HTML](13) [PDF 1088KB](3)
Abstract:
Dongting Lake area is one of the areas with frequent flood disasters in China. With the increasing frequency of extreme weather in recent years, it is of great practical significance to study the flood control situation of Dongting Lake area under historical extreme floods. Taking the floods of the Yangtze River in 1870, 1935 and 1954 as the research object, by establishing a one-dimensional and two-dimensional coupled hydrodynamic model of the Yangtze River, Dongting Lake and flood storage and detention area, the water level and excess flood in Dongting Lake area are simulated under the conditions of existing topography and engineering measures. The results show that under the condition of compensation operation of the Three Gorges and upstream reservoirs, if the floods in 1870, 1935 and 1954 occur, the excess flood volume near Jingjiang River and Chenglingji decreases significantly. Combined with the application of flood storage and detention areas in Jingjiang area and Chenglingji area, Dongting Lake area can safely spend the flood. The regulation and storage of the Three Gorges reservoir has greatly reduced the peak discharge of Zhicheng, the peak discharge of the the three rivers in Southern Jingjiang has also decreased, and the water level of each station in Dongting Lake area has decreased; The application of flood diversion in the flood storage and detention area has reduced the water level of Lianhuatang, increased the water surface gradient of Jingjiang River, and further reduced the peak flow of the three rivers in Southern Jingjiang. Due to the reduction of upstream water and downstream water level, the water level in the lake area has further decreased. By quantitatively predicting the flood control situation of the middle reaches of the Yangtze River and Dongting Lake area, it provides a scientific basis for the governance of Dongting Lake and lays a foundation for improving the management ability of flood control and disaster reduction in the lake area.
Spatial and temporal variation characteristics of the drought-flood abrupt alternations over Haihe River Basin
YANG Yanjuan, CHEN Yuehao, CHEN Sining, XIONG Mingming
 doi: 10.12170/20210114001
[Abstract](34) [FullText HTML](38) [PDF 2174KB](4)
Abstract:
The research on the occurrence regularity of the drought-flood abrupt alternation in Haihe River Basin can provide scientific reference for flood control and drought relief. Based on the daily precipitation data of 159 meteorological stations in Haihe River Basin from 1961 to 2019, the Standardized Antecedent Precipitation Index (SAPI) is calculated. Based on the SAPI, according to the drought-flood grade standard and drought-flood abrupt alternation conditions, the drought-flood abrupt alternation events since 1961 are screened out, and the frequency and intensity characteristics of drought-flood abrupt alternation in Haihe River Basin are analyzed. The results show that the annual average frequency of drought-flood abrupt alternation in Haihe River Basin is 33 times, which basically increases year by year, with an average of 37 times in recent 10 years. The intensity of drought-flood abrupt alternation also showed an upward trend, and increased to above the average value after 2000; it showed a jumping increase with reaching the maximum value especially in recent 10 years. The drought-flood abrupt alternation occurred mostly in May, June and mid September, and less in midsummer. The intensity of drought-flood abrupt alternation presents a single peak distribution, and the maximum value appears from the middle of June to the first ten days of July. The corresponding frequency of drought-flood abrupt alternation is also more in this period, which increases the risk of flood disaster. From the perspective of spatial distribution, the frequency and intensity of drought-flood abrupt alternation are high value areas in the southern part of Luanhe River system, the western part of Beisanhe River system and the central part of TuhaiMajia River. That is to say, the frequency and intensity of drought-flood abrupt alternation are high in these areas, consequently, the risk of drought-flood abrupt alternation is high. These areas may become the focus of flood control.
Study on pore water pressure in concrete under water pressure environment
SUN Bao, PENG Gang, WANG Qianfeng, LIANG Hui
 doi: 10.12170/20190322001
[Abstract](461) [FullText HTML](211) [PDF 764KB](16)
Abstract:
In order to study the change of pore water pressure of concrete in the water pressure environment, the experiment of pore water pressure change of the concrete under different water pressure was carried out. Based on the test data, the transient inversion numerical simulation of pore water pressure variation of concrete under different water pressure is carried out by using the finite element software ANSYS, and the results are compared with the experimental results. The research results show that under the action of water pressure, the change characteristics of pore water pressure of concrete can be divided into three stages: the rapid increase stage, the slow increase stage and the stabilization stage. When the concrete is under the water pressure of 0.875 MPa, the pore water pressure of the concrete reaches the value equal to the applied water pressure for more than 9 h. The variation law of pore water pressure of concrete is in good agreement with the experimental data by using the finite element software ANSYS for numerical simulation.
Display Method:
2022, (3): 1-2.  
[Abstract](9) [FullText HTML](3) [PDF 9292KB](1)
Abstract:
Advances in research on the influence of vegetation on river flow and bank morphology evolution
HAO Youzhi, JIA Dongdong, ZHANG Xingnong, WU Lei, CHEN Changying
2022, (3): 1-11.   doi: 10.12170/20210309003
[Abstract](106) [FullText HTML](220) [PDF 897KB](24)
Abstract:
As an important resistance factor of the river system, vegetation plays a vital role in the evolution of river morphology. The existence of the vegetation above ground structure changes the resistance of the river channel, the shear stress of the river bed, the velocity distribution and the turbulence characteristics of the river flow. At the same time, the existence of the vegetation roots can enhance the strength and stability of the riparian soil. This article reviews the effects of vegetation stems on water flow characteristics and the effects of vegetation roots on the stability of riparian, and points out that in future vegetation water flow research, the influence of vegetation branches and leaves on water flow characteristics, as well as the deformation and swing of flexible vegetation under the action of water flow, should be further considered. And the impact of the boundary conditions of the river forms should be fully considered, particularly the vegetation characteristics of branching river need further studies. In the aspect of vegetation root system for soil consolidation and bank protection, the heterogeneity of the riparian soil, the erosion of the river flow on the riparian, and the impact of water seepage on the mechanical properties of the beach soil should be considered at the same time. In the prediction of vegetation river evolution, the hydrodynamic problems and soil mechanics problems with vegetation and the mutual feedback response mechanism between them should also be comprehensively considered.
2022, (3): 1-2.  
[Abstract](12) [FullText HTML](4) [PDF 369KB](2)
Abstract:
Temporal and spatial distribution characteristics of evapotranspiration in the Huang-Huai-Hai River basin
YANG Xiaotian, ZHANG Jianyun, BAO Zhenxin, WANG Guoqing, GUAN Xiaoxiang, LIU Cuishan, JIN Junliang
2022, (3): 12-22.   doi: 10.12170/20210530002
[Abstract](75) [FullText HTML](48) [PDF 2238KB](11)
Abstract:
Evapotranspiration is a key element connecting the energy cycle and water cycle of the climate system. It is of great significance to explore the evolution of actual evapotranspiration and its influencing factors in the Huang-Huai-Hai (HHH) River basin, which helps to understand the response of the regional water cycle to climate change. To this end, the GLEAM actual evapotranspiration (ET) dataset over the HHH River basin from 1980 to 2018 was collected, together with the parallel Normalized Difference Vegetation Index (NDVI) data and station-based meteorological observations (precipitation and air temperature). The linear regression method, Mann-Kendall trend test and correlation analysis methods were used to analyze the variations of ET and its influencing factors in the research area of interest. The results show that: the accuracy of the verification results between the GLEAM products and the reference value in the HHH River basin was better, and the mean annual ET of the HHH River basin was 474 mm, showing a significant upward trend. In terms of the spatial heterogeneity, the mean annual ET ranged from 183 mm to 708 mm, decreasing from southeast to northwest over the HHH River basin, which had a significant difference in spatial patterns. The spatial distribution of ET in each season with significant differences was basically similar to that of ET at annual scale. Actual evapotranspiration value and NDVI value had a significantly positive correlation, but the former had a mainly positive correlation with precipitation and temperature. The precipitation in the HHH River basin showed an insignificant increase trend, while the temperature showed a significant increase trend. The increase in NDVI was the main reason for the significant increase in actual evapotranspiration in the HHH River basin from 1980—2018.
Impact analysis of cloud water resources utilization on irrigation water demand in North Three Rivers Basin
TIAN Xueying, WANG Gaoxu, WU Yongxiang, WU Wei, LIU Tao
2022, (3): 23-33.   doi: 10.12170/20210727001
[Abstract](37) [FullText HTML](35) [PDF 6111KB](5)
Abstract:
Based on Penman-Monteith formula, a prediction model of irrigation water demand was established to study the variation of irrigation water demand in 11 calculated regions of the North Three Rivers Basin under three inflow frequencies of 95%, 75% and 50%, and four scenarios of no rainfall increased, 5% rainfall increased, 10% rainfall increased and 15% rainfall increased, which is to explore the difference of irrigation water under different inflow conditions and rainfall conditions. The results show that the cloud water resources of the North Three Rivers Basin are rich and the precipitation efficiency is not high, which has great development potential. Crops need a lot of water from May to September. The planting structure and planting area of crops affect irrigation water demand. The irrigation water requirement of the North Three Rivers Basin is the highest in summer, followed by spring and autumn, and the lowest in winter. After analysis, we obtained that the combination of cloud water resources and farmland irrigation and optimizing crops planting structure can bring considerable benefits. During the dry year and extra dry year, summer is suitable for increasing rainfall in the whole basin of the North Three Rivers. Spring and autumn are suitable for increasing rainfall in Chaobaihe mountain area, Jiyunhe mountain area, Tangshan plain area, and Tianjin plain area, etc. The utilization of cloud water resources provides a new source of irrigation water and a new idea for the optimal allocation of water resources.
Dam static and dynamic deformation monitoring based on BeiDou Satellite Navigation System
FAN Mingjie, LI Zhuo
2022, (3): 34-40.   doi: 10.12170/20220115001
[Abstract](49) [FullText HTML](9) [PDF 2510KB](11)
Abstract:
Conventional observation methods for surface deformation of reservoir dams cannot realize automatic observation, and their accuracy is easily affected by visibility and climatic conditions, and the acquisition frequency is low, so they can only monitor static deformation. Through the comparison and analysis of the optical method and the BeiDou Satellite Navigation System (BDS) surface deformation monitoring technology, combined with a reservoir dam project, the feasibility study of the BDS monitoring of the static and dynamic deformation of the reservoir dam surface is carried out in this study. Engineering practice shows that the BDS can not only monitor the static deformation of the dam surface at the millimeter level, but also can observe the dynamic deformation of the dam surface with an acquisition frequency of 1 Hz under the action of earthquakes so as to meet the specification requirements. This provides an effective technical solution for the unified monitoring of static and dynamic deformation of dams in active seismic areas, and is of great significance to post-earthquake dam safety assessment or emergency treatment.
Sedimentation characteristics of the reach from Bayangaole to Toudaoguai of the Yellow River
ZHANG Xiaohua, ZHENG Yanshuang, SHANG Hongxia, FENG Qing
2022, (3): 41-49.   doi: 10.12170/20211214002
[Abstract](27) [FullText HTML](14) [PDF 1162KB](5)
Abstract:
The analysis shows the various sand sources and characteristics of sedimentation in the reach from Bayangaole to Toudaoguai part of Ningmeng reaches of the Yellow River: for a long time (1952—2012), the proportion of fine sands (sediment diameter d≤0.025 mm) of the in-coming sediment is 52.7%, which is dominant. The fine and medium sands (0.025<d≤0.050 mm) and coarse sands (0.050<d≤0.100 mm) all come from the upper reaches of Bayangaole. The proportion of extra coarse sands (d>0.100 mm) in deposition is 56.2%, which is dominant. And the extra coarse sands come from the upper reaches of Bayangaole, tributaries and aeolian sand evenly. The erosion and deposition law of various grain sands is: the erosion and deposition of the fine and medium and coarse sands occur due to flow and sediment conditions, and the extra coarse sands deposit continuously. Therefore, the adjustment characteristics of various grain sands are quite different in each period. In the flood season, the extra coarse sands are the largest part in deposition before 1986, the fine and medium sands are eroded before 1986 and deposit after 1986, and the fine sands are the largest part of deposition. In non-flood season, all the sands are eroded before 1986 and deposit after 1986 mainly due to the fact that fine and medium sands are eroded before 1986 and deposit after 1986, and the deposition of coarse sands increases. The preliminary analysis shows that the sediment erosion and deposition adjustment in the reach from Bayangaole to Toudaoguai in each period depends on the runoff and sediment of the mainstream and flow processes, and is also affected by tributary sand volume. The research results provide a basic support for the control of the susperded river in Ningmeng reaches of the Yellow River.
Permeability coefficient investigation based on fractal characteristics of porous media soil
WANG Yu, GU Yanchang, WANG Shijun, DUAN Xiangbao
2022, (3): 50-58.   doi: 10.12170/20210629001
[Abstract](88) [FullText HTML](38) [PDF 1201KB](16)
Abstract:
Permeability coefficient of soil is extremely important to dike and dam engineering. Scale-invariant space of seepage failure testing soils were statistically analyzed by multifractal dimensions, which shows that fine particle content is the major factor of mass fractal dimension. Based on a pipe bundle model of porous medium, the theoretical relationship between permeability coefficient and porosity was deduced, indicating that the influence factors of permeability coefficient include fractal coefficient, particle size, fractal dimension and fluid viscosity coefficient. The nonlinear relationship of permeability coefficient, porosity and fractal dimension was verified for further studies based on seepage failure experimental results. The results show that when the fractal dimension value is greater than 2.83, porosity decreases obviously with the increase of the fractal dimension, while permeability coefficient decreases insignificantly under the cohesive force of hydroscopic water and film water. The results provide a theoretical base for seepage formation mechanism and evolution process, which can decrease the seepage disaster risk of dams.
Seepage simulation for heterogeneous soil based on the mixed form of Richards’ equation
HE Lingli, TIAN Dongfang
2022, (3): 59-65.   doi: 10.12170/20201209002
[Abstract](29) [FullText HTML](29) [PDF 1403KB](6)
Abstract:
The numerical simulation based on the mixed form of Richards’ equation has the mass conservative property, and can be used to simulate the variably saturated seepage which is prior to other forms of equations. However, on material interface, the distribution of moisture content which is required for the FEM numerical simulation is discontinuous, thus the mixed form of Richards’ equation cannot be utilized in the FEM simulation for heterogeneous soil. In this research, a numerical method was proposed to simulate the variably saturated water flow in heterogeneous soil based on the mixed form of the equation. In the proposed method, two nodal numbers are assigned to each node which locates on the material interface so that the moisture content of each node can be expanded in a truncated Taylor series with respect to pressure head with different material properties. The continuity of the total head is imposed by the Lagrange multiplier method. The proposed method and program based on Matlab were validated against two examples stemmed from other literature. One example was a 1 d problem for the infiltration and draining process of a two layered soil column, and another example was a 2 d infiltration problem for a two layered soil column. And the verification indicated a good agreement between our modeling results and analytical solution for 1 d problem as well as the numerical results for 2 d problem.
Performance of concrete with vacuum dewatering process
OUYANG Youling, FU Yongming, QIAN Wenxun, CHEN Xunjie, CHEN Sixing
2022, (3): 66-73.   doi: 10.12170/20210618001
[Abstract](77) [FullText HTML](45) [PDF 1225KB](3)
Abstract:
In order to improve the permeability resistance of concrete protective layer and avoid surface cracks, and then improve the durability of reinforced concrete, vacuum dewatering process was adopted in this research. The performance of vacuum dewatered concrete and its improvement mechanism were studied by macroscopic performance test and micro pore structure analysis. The test results show that: (1) The vacuum dewatering rate and performance of vacuum dewatered concrete can be improved by using lower initial water-binder ratio, less water consumption per unit and more than about 20% suitable sand ratio compared with non-vacuum dewatered concrete. (2) After vacuum dewatering, the increamental value of compressive strength of concrete after 28 d increases with the water-binder ratio; and the improvement value of concrete abrasion resistance strength after 72 h decreases with the increase of water-binder ratio. And the improvement effect of low water-binder ratio on abrasion resistance strength is particularly significant. (3) Compared with non-vacuum dewatered concrete, the dry shrinkage deformation of vacuum dewatered concrete decreases and the permeability resistance of vacuum dewatered concrete improves significantly. The results of pore structure analysis show that vacuum dewatering process mainly increases the volume content of pore size of 20~50 nm in concrete, and the total porosity, maximum pore size, critical pore size and average pore size of concrete decrease obviously. Vacuum dewatering process optimizes and refines concrete pore structure. Vacuum dewatering process can be used as an effective measure to improve the performance of reinforced concrete protective layer.
Monitoring and analysis on micro-amplitude deformations of a concrete face rock-fill dam with long-term service conditions
DING Yutang, ZHOU Wangjun, CHEN Zhanglun, CHEN Hongfeng, WANG Chaoyi, LU Yangyang
2022, (3): 74-81.   doi: 10.12170/20210523001
[Abstract](31) [FullText HTML](22) [PDF 1920KB](5)
Abstract:
The micro-amplitude deformations of concrete face rockfill dams (CFRDs) can last for a very long time due to creep effect and external influences. The seepage control system such as the concrete face can be damaged if these micro-amplitude deformations continue to grow. Traditional deformation measuring methods are suffering from low accuracy and low frequency, thus the data can hardly reflect the true deformation features of CFRDs. To improve this defect, the Hydrostatic Level System and the Tension Wire Alignment System are applied for measuring the vertical and horizontal surface deformations for Zeya Reservoir dam. After a 5-year continuous monitoring, the monitoring data reveals that: ①The above measuring system can meet the requirements of the long-term and micro-amplitude deformation monitoring. ②The deformaions due to material creep have not stopped even after 20 years, the max average vertial deformation and horizontal deformaion rate can reach 4.33 mm/a and 3.50 mm/a, respectively. ③The deformation rates are reducing gradually, thus the deformations tend to converge. The above findings can provide useful references for monitoring system design and creep behavior studying.
Evolution law of valley deformation during construction of extra-high arch dam
WANG Wenjuan, JI Dingyu, LI Yunzhen
2022, (3): 82-89.   doi: 10.12170/20210426001
[Abstract](14) [FullText HTML](24) [PDF 2094KB](8)
Abstract:
Tracking and analyzing the valley deformation of a high dam during construction is of great significance for high slope stability and dam safety. In this paper, the finite difference method is used to simulate the evolution of valley deformation. Based on the engineering environment and geological structure of an extra-high arch dam, we tracked and analysed the monitoring data of rock mass deformation on both sides of the dam area, and discussed the driving factors and evolution laws of valley deformation during construction in the dam area. The law of valley deformation of the plunge pool behind the dam shows that the variation law of valley deformation at different elevations is similar. The shrinkage deformation has a good positive correlation with the elevation, and the deformation of the part with high elevation is relatively large. Both banks deform towards the river valley, showing a positive correlation with elevation. The deformation speed of the left bank is slightly faster than that of the right bank. The numerical simulation results of deformation are close to the field measured results. The research results can provide a reference for normal water storage in the later stage of the dam.
Experimental study on effects of water content and temperature on mechanical properties of plateau soil
WANG Rui, GUO Jukun, WEI Daokai, BIAN Guijian, LEI Shengyou, QIONG Ji, ZHANG Qingxin
2022, (3): 90-99.   doi: 10.12170/20210822002
[Abstract](30) [FullText HTML](25) [PDF 2841KB](5)
Abstract:
The orthogonal test of mechanical properties of plateau soil is carried out via a self-developed soil freeze-thaw cyclic shear equipment. The compression characteristics, freezing and frost heaving, and shear characteristics of soil affected by temperature and water content are studied. The results show that the normal displacement of soil samples during compression increases with the water content, and the relationship between compression value and normal stress can be described by hyperbolic model. The soil with different water content is frozen when the temperature drops from 0 ℃ to −12 ℃. The temperature of frost heaving of soil with 12% water content ranges from −3 ℃ to −2 ℃. The stress softening characteristics of soil become more and more obvious with the decrease of temperature, and the peak shear stress and residual shear stress are also the largest under negative temperature. The peak shear stress of soil near the optimum water content is the largest. The variation law of normal displacement of soil at −12 ℃ shows shear expansion characteristics under different test conditions, while the soil at 12 ℃ and 0 ℃ shows both dilatancy and shrinkage characteristics at low water content, and only shrinkage characteristics at high water content. The internal friction angle decreases with the content and temperature, and the cohesion decreases with the temperature, and reaches the maximum near the optimum water content.
Discussion of penetration depth of ship anchoring based on finite element method
YU Bowen, CHEN Li, LIU Rui
2022, (3): 100-107.   doi: 10.12170/20210430001
[Abstract](65) [FullText HTML](31) [PDF 1209KB](3)
Abstract:
The accurate calculation of the penetration depth of ship anchoring is of vital importance to the safety of pipeline projects passing through anchorage areas and navigation channels below the riverbed. Based on the results of the ship anchoring experiment, we first study the calculation accuracy of various existing anchor penetration depth calculation methods including empirical method, standard method and theoretical formula method. Then, we take Hall anchor as an example, and use the finite element software ANSYS-DYNA to propose a numerical simulation method of anchor penetration depth that can consider multiple factors such as complex layered soils, bottoming horizontal velocity and bottoming angle. The influence of anchor dragging on penetration depth is also studied in this paper through the method of geometric analysis. The calculation results show that the bottoming horizontal velocity, bottoming angle and anchor dragging have influences on penetration depth, and among them, anchor dragging has the most significant effect, the influence of bottoming angle comes the second place, and bottoming horizontal velocity has the least influence. It can be obviously seen that after considering the impacts of the bottoming horizontal velocity, the bottoming angle and the anchor dragging, the calculation results will be more conducive to ensuring the safety of engineering projects.
Comprehensive assessment of environmental impact of dam breach based on set pair analysis and triangular fuzzy number coupling method
GE Wei, QIN Yupan, LI Zongkun, WANG Te, JIAO Yutie, WANG Jianyou, ZHAO Fengyao
2022, (3): 108-114.   doi: 10.12170/20210619001
[Abstract](69) [FullText HTML](16) [PDF 832KB](2)
Abstract:
This study mainly aims at the problem that there are numerous factors and uncertainties in dam breach environment. The index system and corresponding grade classification standards were established based on the comprehensive analysis of seven environmental factors of dam breach, such as channel morphology and water environment. Considering that set pair analysis deals with the certain and uncertain problems in the evaluation process well, in order to fully express the identity, difference and opposite relations among sets, the original connection number is extended to five element connection numbers and its difference component coefficient is further described in combination with triangular fuzzy number theory. Consequently, the model coupled with set pair analysis and triangular fuzzy number for assessing environment impact of dam breach was established. Taking Shaheji Reservoir dam as an example, the evaluation results of the established coupling model were compared with those of set pair analysis and fuzzy mathematics, which shows that the model is reasonable and effective, hence providing a new way for dam breach environmental impact assessment.
Study on grading degradation of coarse coal slurry pipeline transportation and its influence
ZHAO Li’an, WANG Tieli
2022, (3): 115-121.   doi: 10.12170/20210805003
[Abstract](68) [FullText HTML](71) [PDF 984KB](5)
Abstract:
In view of the lack of research on the prediction of particle gradation degradation in the transportation of coarse particle coal slurry, by using the experimental research method and theoretical analysis method, the mass percentage, viscosity and hydraulic gradient of each particle size in coal slurry at 30, 40, 50 and 60 min are given out. The idea of using grinding theory to study the coal conveying process of coarse coal slurry pipeline is put forward. On this basis, the solution methods of breakage rate function and grinding balance equation are given. The results of data comparison and analysis show that the maximum deviation between the predicted value and the measured value of particle gradation is no more than 12.53% when the coal slurry is transported for 30 and 50 min. With the extension of conveying time of coarse coal slurry, the relative viscosity of coal slurry gradually increases, mainly due to the refinement of coarse particles above 2.0 mm and the increase of particle content below 0.074 mm. The reduction of hydraulic gradient caused by particle grading degradation is mainly due to the reduction of settlement velocity caused by coarse particle refinement and the reduction of the probability of particle contact with the bottom of the pipeline.
Experiment study on reinforcement of PCCP inside with circumferential pre-stressed carbon fiber plate
LU Wenyan, LIU Haixiang, KE Minyong, XU Minfan, LÜ Kangwei, HONG Xin
2022, (3): 122-126.   doi: 10.12170/20210513003
[Abstract](42) [FullText HTML](30) [PDF 2272KB](6)
Abstract:
In order to repair the damaged prestressed concrete cylinder pipe (PCCP) which is hard to be excavated timely and effectively, so as to reduce or even avoid PCCP burst, the reinforcement technology of circumferential pre-stressed carbon fiber plate in PCCP was proposed. This technology pre-stresses the carbon fiber plate inside the pipe, and sticks it to the inner wall of PCCP with high-performance structural adhesive. PCCP is strengthened with a higher bearing capacity. A test of concrete inner ring combined with outer ring was designed to verify the feasibility of the reinforcement method and optimize the construction technology. The test showed that the pre-tensioned CFRP was successfully bonded to the outer concrete ring. After roughening and base treatment of the surface of concrete, the system formed by concrete, adhesive and pre-stressed carbon fiber plate was reliable, and could provide a bond strength of no less than 0.8 MPa. The test result indicates the foundation test scheme and reinforcement scheme are feasible. A further test scheme to strengthen PCCP is put forward with end-to-end carbon fiber plate.
Structural safety and stability analysis of internal water-filled steel cofferdam
ZHANG Yu, ZHAO Jiyun, LIU Mingxiao, SUN Dongpo
2022, (3): 127-135.   doi: 10.12170/20211002003
[Abstract](17) [FullText HTML](8) [PDF 2840KB](7)
Abstract:
The appropriative steel cofferdam for slope restoration of a large aqueduct is a kind of underwater steel structure, moving externally and statoc internally, and its structural stability is fundamental under working conditions. According to the design structure condition of the steel cofferdam and considering its dynamic and static loads in water, the mechanical analysis of fluid-structure coupling (FSI) system is made. Firstly, the load characteristics of the steel cofferdam are analyzed, and the tanglesome load condition of the flow field around the steel cofferdam is simplified to the hydrodynamic pressure acting on the structure. Secondly, a finite element model of cofferdam structure is constructed. Numerical simulation software ANSYS is used to analyze the stress state of each component and the characteristics of the whole structure. Studies show that the axial stress of the upstream bracing piece is larger than the Euler critical stress, and the deformation of the guide groove and the faceplate is quite large, which requires structural adjustment, while the stability of the middle and downstream bracing piece meets the requirements. By optimizing and adjusting the structure, the method of ameliorating the structure is put forward, and is successfully applied in engineering practice, thus providing a theoretical support for ameliorating the design of the steel cofferdam.
Analysis of autogenous shrinkage and pore structure of cement mortar with low-activity slag as internal curing material
DU Yuhui, LI Shuangxi
2022, (3): 136-144.   doi: 10.12170/20210628001
[Abstract](52) [FullText HTML](39) [PDF 1886KB](4)
Abstract:
The pre-saturated low-activity slag was used as a partial replacement of sand for internal curing materials. The mechanical properties and autogenous shrinkage of internal curing mortar with different low-activity slag contents were studied. The microscopic mechanism of low-activity slag internal curing mortar was discussed based on MIP, SEM and XRD test results. The results show that the compressive strength development law of mortar specimens with different low-activity slag contents under standard curing and sealing curing conditions is similar, that is, with the increase of low-active slag content, the early strength of mortar decreases greatly, but with the extension of age, the late strength reduction of mortar is less than early strength reduction. Moreover, low-activity slag can effectively inhibit the autogenous shrinkage of the slurry at various stages, especially in the rapid shrinkage stage and the transient expansion stage. Under the internal curing effect of low-activity slag, although the porosity of the slurry is increased, the average pore diameter is effectively reduced, the distribution ratio of various types of pores is improved, and the pore structure is refined. The hydration product C-S-H gel increases, Ca(OH)2 is consumed, and the weak structure of the interface transition zone is significantly improved.
Concurrent multi-scale domain decomposition method for four-point bending test of concrete beam
QIU Liting, MA Fuheng, SHEN Zhenzhong, ZHANG Zhan, HUO Jixiang
2022, (3): 145-152.   doi: 10.12170/20210405001
[Abstract](86) [FullText HTML](54) [PDF 1604KB](7)
Abstract:
Damage plays an important role in nonlinear mechanical properties of quasi-brittle concrete materials. However, there are problems of grid sensitivity and zero energy consumption when local damage model is used in finite element method. At the same time, the traditional single mesh finite element model is difficult to treat the linear elastic region and nonlinear region of component in a different way, which can not focus the limited computation costs on the key areas. Through pre-setting high-precision finite element grids in local sub-domains and introducing inter-scale linear multi-point constraint methods, the concurrent multi-scale method and the total-finite element tearing and interconnecting method were combined. Meanwhile, the gradient-enhanced continuum damage model was applied to describe the nonlinear behavior of concrete. Furthermore, the dual assembly method was used to solve the large linear equations of the model. Then a concurrent multi-scale domain decomposition method was proposed for concrete failure analysis. The model was used to simulate the four-point bending test of a single notched concrete beam. Finite element meshes with three different precisions were generated for the pure bending regions where damage may emerge. The numerical results can reproduce the failure mode of concrete specimen, the model is reasonable and not mesh sensitive, which can provide a multi-scale numerical simulation technical support to explore the failure of concrete components with a clear damage pattern.

Supervisor:Ministry of Water Resources of the People's Republic of China

Sponsor:Nanjing Academy of Water Conservancy Sciences

Editor-in-Chief:Hu Yaan

Address:No. 34 Huluoguan, Nanjing

PostCode:210024

Tel:025-85829135

Email:jnhri@nhri.cn

ISSN:1009-640X

CN:32-1613/TV

Postal Distributing Code: 28-19

Unit-Price: 30 RMB/Issue

Total-Price: 180 RMB/Year

Publication Period: Bimonthly (1979 initial issiue)

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