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doi: 10.12170/20201213001
Abstract:
Deformation prediction model provides an essential support for the analysis of dam structure safety. However, the existing dam deformation prediction models suffer from low precision and insufficient generalization. To solve this problem, an adaptive fuzzy neural network was introduced into the dam deformation prediction model in this study. Specifically, the particle swarm optimization (PSO) algorithm with dynamic weights was applied to optimize the parameter of fitness values in the fuzzy layer of the adaptive fuzzy neural network. Based on this, an adaptive fuzzy neural network called DPSO-ANFIS is formed, which is capable to search for the optimal fitness value. And a dam deformation prediction model based on DPSO-ANFIS was established. Experiments were conducted to verify the effectiveness of the proposed deformation prediction model. The monitoring data from the dam prototype was applied to the trained model to obtain the output values, and these values were then compared with the actual monitoring data. The engineering practice showed that the maximum deviation between the output values of the dam deformation prediction model based on DPSO-ANFIS and the measured values was 0.0516 mm; the RMSE (root mean square error) was 0.0351, and the average absolute error was 0.0320. All the values of these performance indicators were better than that of the dam deformation prediction models based on PSO-ANFIS, ANFIS, and BP neural network. As for the measure points and time, the predicted values from the dam deformation prediction model based on DPSO-ANFIS exhibited a trend much close to that of measured values. Also, the proposed deformation prediction model achieved a stable overall prediction performance. Therefore, the dam deformation prediction model based on DPSO-ANFIS achieves high accuracy, good generalization, strong stability, and excellent comprehensive performance in practical engineering applications.
doi: 10.12170/20201106002
Abstract:
Stress and deformation state of sheet pile wharf are important standards for its safe operation. Based on the results of distributed optical fiber model test and application research, a new distributed monitoring technology for stress and deformation of piles is proposed in this paper, which has been successfully applied to the prototype test of reinforced concrete cast-in-situ piles for sheet pile wharf. This monitoring method can overcome the shortcomings of traditional point monitoring methods in terms of resolution and accuracy, and realize the real-time monitoring for pile structure in full depth and full period of construction. The measurement results can accurately reflect the distribution of deformation, bending moment and stress along the pile length during the whole process of harbor basin excavation, and effectively evaluate the operation and construction conditions in time, which can provide safety guarantee and guidance for the continuous stable operation of sheet pile wharf, and has certain engineering practical significance.
doi: 10.12170/20200827002
Abstract:
River clogging is a natural disaster caused by landslide which result by earthquake, rainfall and other factors. Among the many losses caused by river clogging disaster, the loss of life is the most serious loss. In this paper, according to the disaster mechanism of life loss because of river clogging, the evaluation index system including risk population, warning time, understanding degree, lake level rising speed, elevation of risk population, submerged depth and other parameters, and the quantitative evaluation method of each parameter is established. At the same time, a bayesian network model, consisting of emergency evacuation network, submerged water depth network and life loss quantitative assessment network, is established through the interaction among various factors to assess the life loss of river weir, and the case of Niulan River weir is used to verify the rationality of the assessment method.
doi: 10.12170/20210105002
[Abstract](13) [FullText HTML](7) [PDF 1247KB](4)
Abstract:
The local scour around bridge piers is one of the main safety influence factors of sea-crossing bridges in the nearshore region. Based on the survey data of six bridge piers of Jintang Sea-Crossing Bridge in Hangzhou Bay during 2014, 2015 and 2017, the scour effects around the bridge piers under bidirectional tidal flows were systematically studied. The general scour depth and the maximum local scour depth were analyzed respectively. It is found that the general scour depth is about 3.3~3.6 m, while the average local scour depth is about 8.3 m. The local scour holes extend in both upstream and downstream directions with elliptic shapes due to bidirectional tidal flows. The longitudinal length of scour hole is approximately linear with the maximum local scour depth with a ratio of about 10~12. While the scour hole width of each bridge pier is nearly the same, about 4~5 times the pier width. In addition, there is no obvious correlation between the width of scour hole and the maximum local scour depth. The research results about scour depth prediction and scour profile characteristics can provide a reference for sea-crossing bridge foundation design, maintenance and scour protection.
doi: 10.12170/20200825004
[Abstract](11) [FullText HTML](3) [PDF 1501KB](1)
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In the failure process of rock specimen with double cracks, the stress field between the different cracks will interact, and the rock bridge area will coalesce. In this paper, the strain strength criterion is embedded into the expanded discrete element program UDEC which was secondary developed to simulate the propagation of tensile crack and shear crack of specimens with prefabricated double cracks. According to the results of the numerical simulation, four basic coalescence modes of rock bridges will appear in the double-crack specimen during uniaxial compression: (1) Non-coalescence mode, the wing cracks at the tips of the two prefabricated cracks gradually expand independently, but the discontinuous mode of penetration does not occur in the rock bridge area; (2) Shear coalescence mode, in the rock bridge area, the main stress field and the shear stress field are concentrated, resulting in shear cracks coalesce the rock bridge. At this time, the shear stress plays a leading role in the shear coalescence mode; (3) Tensile coalescence mode, tensile cracks penetrates the rock bridge, the rock bridge is highly concentrated by the principal stress field. At this time, the rock bridge penetration has the characteristics of instantaneousness, and the tensile crack penetrates the tensile coalescence mode of the rock bridge; (4) Mixed coalescence mode, under the combined action of tensile force and shear force, the rock bridge coalesce the mixed tensile and shear coalescence mode after the specimen reaches the highest peak strength. Through comparison with laboratory tests, it is concluded that applying the strain strength criterion to the numerical simulation analysis can more accurately describe the changes of stress and strain and the penetration of rock bridges during mesoscopic failure, and enrich the mechanism penetration of multi-crack rock specimen in mesomechanics. It provides a reference for numerical simulation in studying the actual engineering of rock mass meso-damage.
doi: 10.12170/20201119001
[Abstract](17) [FullText HTML](6) [PDF 1107KB](3)
Abstract:
At the end of year 2018, the total number of built reservoirs in China reached 98, 822, with a total storage capacity of 895.3 billion m3. Reservoirs are not only important parts of national flood defense system, but also are key engineering measures to optimize the allocation of water resources. However, once a dam failure incident happens, it will involve major public safety. In-depth analysis of the historical data of dam failure cases is of great significance for preventing dam failure and improving the management level of disaster prevention and mitigation. Based on the collection of 3541 dam failure cases occurred in China from 1954 to 2018, this paper focuses on 84 dam failure cases that occurred from 2000 to 2018. Detailed statistical analysis of the dam failure cases is carried out from the perspective of spatial distribution, reservoir size, dam height, type, failure causes, and other aspects. The trend characteristics of dam failure cases since 2000 can be summarized as: (i) Over-standard flooding becomes the main cause of dam failure cases of overtopping; (ii) Dam failure cases caused by quality defects at different locations of reservoirs significantly increased; (iii) The dam failure rate in the western part of China is dramatically higher than in other regions; (iv) Improper operation and management of reservoirs has become an important reason of dam failure incidents. Based on the aforementioned analysis, suggestions for further strengthening the dam safety management are proposed including that more attention should be paid to the impact of climate change on reservoirs, the engineering construction and operation safety supervision system should be continuously optimized, the management and operation conditions in the central and western regions of China should be intrinsically improved, and engineering measures and non-engineering measurements should be taken into account simultaneously in the field of dam safety management.
doi: 10.12170/20210422001
Abstract:
The Yangtze Estuary is a giant multi-channel bifurcated river-tide system, which is affected by medium-intensity tides (mainly semilunar tides) and obvious seasonal variation of riverine inflow, and its hyrodynamic-morphological conditions are very complex. In this paper, the response of discharge to the dynamic characteristics of water and sediment in the maximum turbidity area of the Yangtze Estuary is studied. The research results show that the increase of discharge means the increase of hydrodynamics, which first has two consequences: one is the enhancement of sediment resuspension capacity, the other is the increase of transport capacity; in addition, in the maximum turbidity area of the estuary, because of the river effect, there is often an increase in estuarine circulation, and the change of discharge also means that the transport capacity from the bottom to land also changes. The measured data and mathematical model jointly show that for the Yangtze Estuary, the larger the discharge is, the greater the sediment concentration of the beach with low velocity will be, but in the main flow area, due to the triple effect of the increase of discharge, the sediment concentration in the maximum turbidity area does not increase in one direction. Sediment concentration in the maximum turbidity area reaches the maximum under the discharge of 30, 000-40, 000 m3/s. This study clarifies the sediment suspension state of the estuary under different discharge conditions, which can provide reference for the development and utilization of soil and water resources, ecological environment protection and waterway dredging maintenance in the Yangtze Estuary.
doi: 10.12170/20201026001
[Abstract](23) [FullText HTML](14) [PDF 2778KB](1)
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In the Jiangsu reach of the Yangtze River, one of the most common silting-promoting structures in the cave collapses is tree top-stone. As cutting trees has negative impact on greening and ecology, a kind of curtain-stone composed of floating block, cloth (or geotextile) and stone is invented. This curtain-stone can block the flow and promote the siltation, which is seldom studied. Based on the force analysis of the curtain-stone placed in the equilibrium state in the flow, the differential equations of the forces acting on the curtain-stone micro element are listed, and then the distribution curve (surface) of the curtain-stone along the water depth can be solved, and the relevant coefficients in the curve are determined from the test data. The formula can be used to determine the horizontal projection length and buoyancy of curtain-stone, and also explain the mechanical mechanism of the floating block floating on or submerged in the water, and the curtain floating on or submerged in the river bottom. A local model of the pit collapse near Zhinan village in the Yangzhong section of the Yangtze River is established. The water blocking effects of curtain-stone and tree head-stone are compared in the scour pools of the model. And the water blocking effect results are the same. The use of curtain-stone can reduce the impact on ecology.
doi: 10.12170/20201029001
[Abstract](35) [FullText HTML](13) [PDF 1444KB](5)
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The debris flow has the characteristics of suddenness, fast flow speed and strong destructive force. It is of great practical significance and theoretical value to study its dynamic mechanism and accurately simulate the formation process. This model was created in the framework of a Godunov-type finite volume scheme to solve the shallow water equations (SWEs). At the same time, the introduction of Graphics Processing Unit (GPU) improved computing technology greatly, and increased the computing speed. Taking the dam-breaking flume debris flow movement characteristics and the prediction of the risk range of the landslide and debris flow in Pusa Village, Guizhou Province as a simulation reference, the constructed GAST model was used to complete the simulation of the debris flow tank test and the prediction of the risk range. The results show that the numerical simulation is in good agreement with the measured results; the application of GPU acceleration technology effectively solves the large amount of calculation in the process of debris flow simulation problem; and the model runs fast and efficiently on the PC. The model is an ideal tool to study the sudden debris flow process, and can provide timely and accurate decision support for disaster prediction.
doi: 10.12170/20210114003
[Abstract](18) [FullText HTML](5) [PDF 1632KB](2)
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The effect of valley width deformation during the initial impoundment stage on the subsequent working behavior and the long-term safety of an arch dam has become an increasingly important chanllenge faced by dam engineering and academia. This study aims to analyze the sensitivity of valley width deformation to the absorption curve of fractured rock mass to address the challenge of valley width reduction during impoundment of the Jinping Ⅰ arch dam in China. The methods of unsaturated seepage analysis theory and nonlinear finite element numerical analysis were applied to study the law of valley width deformation during unsaturated seepage process. The influence of valley width deformation on the displacement and stress of the dam was analyzed. The results showed that the slope on both sides of the valley deformed towards the center under the action of the unsaturated seepage field. The deformation of valley width upstream exceeded that downstream. The valley width deformation increased with an increasing elevation of the water level, and maximum valley width reduction occurred in the saturated seepage field. The distribution of displacement and stress of the dam changed little during the unsaturated seepage process. However, the maximum longitudinal displacement and the minor principal stress of the dam decreased gradually with increaseing elevation of the water level. There was a gradul increase in the major principal stress. The valley width reduction had a squeezing effect on the dam body, resulting in a decrease in the maximum longitudinal displacement, the transfer of the major principal tensile stress from the dam heel to the upstream side of the dam abutment, and the extension of the high-pressure stress zone on the downstream surface to the middle of the crown cantilever. The influence of the saturated seepage field on the displacement and stress of the dam was more obvious than that of the unsaturated seepage field. However, the valley width deformation resulting from the seepage field had a limited effect on the displacement and stress of the dam, which would not affect the overall stability of the dam.
doi: 10.12170/20210116001
Abstract:
In order to explore the influence of the severe weather in the seasonal freezing area on the expansion and contraction deformation and physical and mechanical properties of the canal base expansive soil with different water content, the expansive soil in the Altay area of northern Xinjiang is taken as the research object, and the actual freeze-thaw changes in the northern Xinjiang area are simulated indoor The freeze-thaw cycle test under climatic conditions. Based on this, the volumetric deformation test, unconfined compressive strength test and scanning electron microscope (SEM) test of the expansive soil with moisture content of 12%, 16%, and 20% are carried out, focusing on the analysis of the freeze-thaw cycle. The law of influence of action on volume deformation and mechanical properties of expansive soil. The results show that during the freeze-thaw cycle, with the increase of water content, the volume deformation of the sample changes from "freeze shrinkage and thaw expansion" to "freeze heave and thaw shrinkage". The characteristics of the stress-strain curve are closely related to the number of freeze-thaw cycles and the moisture content. The unconfined compressive strength of the sample decreases with the increase of the moisture content and the number of freeze-thaw cycles. Among them, the first freeze-thaw cycle is the most obvious, and it stabilizes after three times. The function fitting shows that the unconfined compressive strength of the sample has an obvious natural exponential relationship with the number of freeze-thaw cycles. The greater the water content, the greater the influence of freeze-thaw cycles on the microstructure of the soil; the porosity of the soil gradually increases with the increase in the number of freeze-thaw cycles. The first freeze-thaw cycle has the most obvious effect, which appears as freezing macroscopically. The effect of freeze-thawing cycle on the degradation of soil mechanical properties.
doi: 10.12170/20201128001
Abstract:
The characteristics of fish convection field were analyzed by in-situ observation and numerical simulation. The numerical simulation model of the flow field under the dam of Cuijiaying hydroproject is constructed to calculate the downstream flow field of the hydroproject under different operation conditions in the migratory season, and the distribution characteristics of water depth, velocity and other hydraulic elements are counted. Combined with the observation of the downstream fish cluster distribution in the same period, the response relationship of fish cluster to the flow field is revealed through the comprehensive comparative analysis of fish cluster distribution and flow field characteristic distribution, and the response of fish cluster to the flow field is proposed The preference curve of flow field characteristics provides support for the scientific formulation of ecological operation scheme of Cuijiaying hub.
doi: 10.12170/20200828001
[Abstract](14) [FullText HTML](17) [PDF 1217KB](2)
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Deformation is a key indicator for analyzing the characteristics and evaluating the safety of embankment. In this research, the installation method of sensing fiber equipped with an auxiliary structure was designed for the distributed monitoring of embankment’s internal two-dimensional deformation. A distributed monitoring test was conducted on a prototype embankment and the test result of its internal deformation validated the measurement accuracy and feasibility of the distributed monitoring technology as the maximum absolute error between the test result and the actual measured result of the embankment’s two-dimensional deformation was 4.3 mm; and mm-level measurement accuracy was realized not only for the internal two-dimensional deformation at certain points, but also for the whole section of the embankment, which proves the applicability and advancement of the fibre-optical distributed monitoring technology of the two-dimensional deformation inside the embankment.
doi: 10.12170/20200904002
[Abstract](21) [FullText HTML](9) [PDF 1317KB](2)
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Understanding the changes in the regime of precipitation intensity plays an important role in flood risk mitigation and water resources management. Based on the field data of daily and hourly precipitation from 9 rainfall gauge stations in the Rouyuanchuan watershed from 1980 to 2017 and 10 rainfall gauge stations in the Heshuichuan watershed from 1981 to 2017, the changes in the regimes of annual maximum precipitation intensity of 1 h (Ih) and 1 d (Id) and graded precipitation intensity are analyzed using the MK trend test method. Results indicate that:(1) Spatial distributions of Ih and Id are found quite different, with the spatial variation coefficient (CV) of Ih greater than that of Id, and CV of Ih and Id in the Heshuichuan watershed greater than that in Rouyuanchuan. (2) CV of Id in the Rouyuanchuan watershed is found to increase significantly (α=0.05) at a rate of 0.018/10 a while that in the Heshuichuan watershed is found to decrease significantly at a rate of −0.039/10 a. (3) The extreme Id values in the Rouyuanchuan watershed are found to increase significantly at a rate of 7.68 mm/(d·10 a). (4) It is found that no significant change of graded precipitation intensity happens in the Rouyuanchuan watershed while the precipitation intensity of moderate-grade rains and heavy-grade rains in the Heshuichuan watershed show significant increases at rates of 0.61 and 1.29 mm/(d·10 a), respectively.
doi: 10.12170/20200830001
[Abstract](19) [FullText HTML](11) [PDF 933KB](1)
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The reconstruction and extension project of the long-distance water transfer canal in Northern Xinjiang is key to water delivery efficiency and project safety. In order to solve the existing problems of expansive soil, the new and old anti-seepage geomembrane connection, easy deformation of drainage pipes, and labor force shortage, the multi-functional gapping machine, concrete surface molding machine and other integrated machines were developed, construction efficiency and project safety were enhanced, and the demanded labors were sharply reduced. The KS hot melt adhesive bonding and inner tube spinning geomembrane technology were developed by laboratory test and field demonstration, which ensured the efficient connection of new and old impermeable geomembranes. The deformation resetting device of deeply buried underground hose was developed, through which the blockage of the water body in the foundation of the canal could be unclogged quickly, thus avoiding large excavation and providing support for the long-term safe operation of the channel. A series of equipment and technologies have been demonstrated and applied in the north Xinjiang water supply project, and produced great social and economic benefits. The research results have important reference values to the reconstruction and expansion of similar channel projects.
doi: 10.12170/20200805001
[Abstract](18) [FullText HTML](18) [PDF 1682KB](6)
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A nested morphodynamic model of the Tongzhou Bay and its surrounding sea areas is set up with ADCIRC+SWAN and Delft3D+SWAN models. All Typhoons that affected the Tongzhou Bay during 1949 to 2019 are classified into five types according to the characteristics of their tracks, and for each type a typical typhoon is selected to drive the model. The morphodynamic changes of the study area induced by the typical typhoons are simulated, and the responses of channel-sand system in Tongzhou Bay and its surrounding sea areas to storm surges are analyzed. The results show that the thickness of sediment erosion and deposition in the planning port area during a typical typhoon process is generally small, within about ±0.40 m. The erosion and sedimentation induced by the north-passing typhoon and the east-passing typhoon are relatively large. Generally, siltation usually occurs outside of the entrance of the Basin 3 of the Tongzhou Bay port area, while erosion usually occurs in the Yaosha and Lengjiasha shoals. After a typhoon processes, obvious siltation occurred in the outer channel of Lengjiasha in the north of the port area, and obvious erosion occurred in the original Lengjiasha shoal area. Although the amount of siltation/erosion induced by one storm process is not large enough to affect the port operation and navigation, attention should be paid to the impacts of such siltation/erosion in a long-term time scale.
doi: 10.12170/20200824002
[Abstract](15) [FullText HTML](8) [PDF 1093KB](2)
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Prediction of seepage water level extremum is one of the main means to monitor the safety of the earth rock dam, and dam body seepage water level is an important physical quantity to evaluate the seepage characteristics of the earth rock dam. Currently, the common sense of the extreme value prediction methods is on the prerequisite of giving correct independent variables, when such methods being applied. The most important factor affecting the seepage water level extremum is the upstream water level. When the correlation between the seepage water level extremum and the upstream water level is quite good, the predication accuracy provided by conventional models is quite high; when the correlation between the seepage water level extremum and the upstream water level is weak, the predication accuracy provided by conventional models is low. To resolve this issue, this paper proposes a method of predicting and evaluating the seepage water level extremum, which considers the measured value sequence only and neglects the independent variables. Based on the maximum Lyapunov index, a prediction model is established, and the ergodicity and stationary distribution of Markov chain are applied to evaluate this independent variable model. The example shows that the prediction effect of the prediction model based on maximum Lyapunov index is better than that of conventional methods for seepage water level extremum, which has weak correlation with independent variables, and the error assessment model based on Markov chain provides reasonable evaluation. The prediction model and evaluation method based on chaos theory and stochastic process that is proposed in this paper can form a systematic approach to the sequence prediction as well as evaluation method with high accuracy and strong practicability, covering the weak area of conventional prediction methods. It can be used to establish the prediction model for the measured value sequence with uncertain independent variables.
doi: 10.12170/20200909002
[Abstract](18) [FullText HTML](9) [PDF 1141KB](1)
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With the increasing application of geotechnical centrifuge model tests and the increasing demand of quantitative analysis, influencing factor and precise control of sample preparation on porosity and void distribution have arisen as a key issue in the development of geotechnical centrifuge modeling techniques. Sand pluviation is an important technique for preparing sand models and widely employed in geotechnical centrifuge modeling, due to the process of its reconstitution similar to the formation of natural coarse sand strata and the advantages of avoiding soil grain crushing and achieving a wide range of relative density. In order to understand the effect of control factors on the porosity of samples prepared by sand pluviation, a discrete element method based on PFC3D is established to simulate the process of sample reconstitution using sand pluviaiton. Through discrete element simulation of the effect of drop height, mesh-grain size ratio, environmental medium, the feasibility of the proposed discrete element method is properly validated with the general knowledge from physical model tests. The results show that the porosity and the drop height appear in an obvious negative correlation, and the rate of decreasing in the porosity gradually attenuates with the increase of drop height. Meanwhile, a positive correlation exists between the mesh-grain size ratio and the porosity, and the latter is found to distinctly increase with the increasing of the former. The density of environmental medium is exhibited in a significant negative correlation with the porosity and has an important influence. Consequently, the layer thickness of model surface water plays a leading role in the control of the porosity.
doi: 10.12170/20200826002
Abstract:
Gravelly soil has been mostly used as the core material of the high earth-rock dam. When the coarse-grained content of a gravelly soil (referring to the mass fraction, the same below) may exceed 50%, the coefficient of permeability of a gravelly soil is highly likely to fail to meet engineering specifications or standards. This is deleterious to the seepage stability of a dam. Three-dimensional finite element numerical simulation was conducted to study the influence of a gravelly soil having a coarse-grained content of greater than 50% on the seepage through a high earth-rock dam. The coefficient of permeability of elements having a coarse-grained content of greater than 50% is assigned a different value compared with those elements having a coarse-grained content equal to 50% in the simulation. The results show that the gravelly soil in the different parts of the core having a coarse-grained content of greater than 55% had little effect on the seepage field and the seepage discharge through the dam, but exerted a significant influence on the seepage gradient. The maximum seepage gradient occurred at the element having a coarse-grained content equal to 50%. For those cases having a coarse-grained content of less than 55% in the lower and middle parts of the core, the increase in the maximum seepage gradient was 36.4%. For those cases having a coarse-grained content of greater than 55% in the lower and middle parts of the core, the increase in the maximum gradient was even higher, and might exceed the allowable seepage gradient, with adverse effects upon dam safety. Therefore, in practice, the downstream filter should be designed based on the grading and the fine particle content of such gravelly soils. Besides, the relative density of such gravelly soil should be controlled to ensure the safety of the body of the dam.
doi: 10.12170/20200829001
Abstract:
The coefficient of permeability of aquifer is an important hydrogeological parameter in foundation pit dewatering design. The calculated coefficient of permeability of the same soil layer by different calculation methods may be different, thus it is very important to select the most suitable calculation method for a certain soil layer to avoid large errors. Based on the test results of single well pumping tests in sandy cobble ground, four common methods, i.e. Dupuit-Kusargent method, Thiem method, straight-line slope method and water level recovery method are used to calculate the coefficient of permeability of aquifer. The difference between the simulated water level and the field measured value is compared, the reasons resulted in the differences are discussed, and the advantages, disadvantages and applicability of each method are pointed out. The analysis results show that the error of Dupuit-Kusargent method is the largest, that of the straight-line slope method is the second, and the error of water level recovery method and Thiem method is small. Furthermore, the results from Dupuit-Kusargent method are greatly affected by the pumping flow rate, its consistency is poor. The consistency of the results from other methods are good. For determination of the coefficient of permeability for sandy cobble aquifer, Thiem method should be preferred when there are more than two observation wells. The straight-line slope method can be used when there is an observation well, and the falling depth and the logarithm of time are in good agreement with the linear relationship. The water level recovery method can be used when there is no observation well. It is not recommended to use Dupuit-Kusargent method due to its large error.
doi: 10.12170/20200912001
[Abstract](20) [FullText HTML](10) [PDF 1444KB](4)
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To study the influence of dip angle of rock bridge on rock mechanical behavior and crack propagation mechanism, the particle parallel bonding model in the PFC3D code was used to obtain a group of microscopic parameters, which could reflect the macroscopic mechanical properties of intact granite via the trial and error method. A numerical model of the combination of micro-void and parallel fissures ① and ② under different rock bridge angles was established, and the deformation and failure process of the sample in the triaxial compression were analyzed. Results show there was no significant effect on the ratio of the initiation strength to the peak strength; when α = 0° and 75°, the crack propagation modes were similar, and wing cracks were initiated at the inner and outer tips of the fissure ① and ②, and then coalesced with the micro-void; when α=15°, 30°, and 90°, the crack propagation mode was relatively close, the wing cracks could be observed at the tips of the fissures ① and ②; when α=45°, 60°, the cracks grew in a similar manner, there were crack coalescence on the shear plane between the fissures ① and ② and the micro-void, and there were shear cracks at the outer tips of the fissures ① and ②. In this case, both the parallel fissures and the micro-void were on the shear plane; the number of shear cracks was far more numerous than that of the tensile cracks, and the micro-cracks extended from the initial damage zone. mage zone.
doi: 10.12170/20200610001
[Abstract](67) [FullText HTML](27) [PDF 1217KB](39)
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The complex nonlinear mapping relationship between the deformation of gravity dam and various environmental quantities makes the input independent variables of the deformation prediction model have high dimension, which affects the accuracy and generalization ability of the prediction model to some extent. To solve the problems, a combined prediction model is proposed, which combines principal component analysis, the cuckoo search algorithm, and the nuclear limit learning machine network. The model uses the principal component analysis method to extract the main component information of the water level, temperature, and time-dependent influencing factors related to deformation, and optimize the input of variables of the network model; furthermore, it uses the cuckoo search algorithm, which exhibits better optimization performance; than, to determine the kernel parameters and regularization coefficients of the kernel extreme learning machine network. With the measured data of a gravity dam, the deformation displacement of the dam in the direction of the dam axis and the upstream and downstream directions are predicted, compared with those of various models, and evaluated with different quantitative indicators. The analysis results reveal that the certainty coefficients R2, of the proposed model in the two different directions are 0.943 and 0.931, respectively, which are higher than those of the traditional neural network model and the stepwise regression model. In the upstream and downstream direction deformation predictions of different measurement points, the accuracy and generalization ability of the model are better than those of the comparison model, thus verifying the feasibility and advantages of the model.
doi: 10.12170/20200728003
Abstract:
The proposed Three Gorges New Channel 's super-long water conveyance corridor runs at high head, high flow, short time and long distance. The water flow is strongly non-constant. It is very important to ensure safe operation of the ship lock. Therefore, aiming at the super-long water conveyance corridor of the last stage of the high head lock, this paper numerically simulates the unsteady hydrodynamic characteristics of the water flow during valve opening. With this mathematical model, the evolution rules of the flow and the water level of the ship lock chamber and the valve door well are studied under different water conveyance corridor lengths and different valve opening times. The results show that longer length of the water conveyance corridor of the ship lock will increase the value and period of inertial superfall, extend the drainage time, reduce the lifting speed of lock chamber water level and decrease the reduction of the valve well water level during valve opening. Increasing the valve opening rate will reduce the drainage time, increase the lifting speed of lock chamber water level and decrease the reduction of the valve well water level during valve opening, but it can’t change the value and fluctuation period of inertial superfall. These results can be used as a reference for the design of the ultra-long discharge corridor in last stage one of the Three Gorges New Channel.
doi: 10.12170/20210207001
[Abstract](4) [FullText HTML](2) [PDF 0KB](0)
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The traditional analytic hierarchy process shows the problem of the possibility of cumbersome calculation and serious inconsistency. Aiming at that, we comprehensively consider the advantages of the optimal transfer matrix and the "three-scale method" to establish an improved analytic hierarchy process. A waterway ecological evaluation system, which consisted of 1 target, 6 criteria, and 17 indicators, was constructed with reference to the basis of existing research. Taking the Jingjiang Reach of the Middle Yangtze River as an example, we evaluated and compared the situation of the waterway regulation works in 2011 (before regulation) and 2015 (after regulation) and concluded that the Channel Health Index (ICH) increased from “good” (in 2011 with ICH=3.432) to “excellent” (in 2015 with ICH=4.187). The ecology of the Jingjiang Channel exhibits significant improvement after the waterway regulation works. The 6 functions under the criterion level are classified into 4 types of influencing factors, according to the reasons for the increase of the health index. The relative deviations of the results calculated by the improved analytic hierarchy process and the traditional analytic hierarchy process are 0.94% (2011) and 0.40% (2015), respectively, which means that the improved analytic hierarchy process simplifies the evaluation scale of the comparison matrix and optimizes the consistency of the matrix while ensuring the accuracy of the calculation results.
doi: 10.12170/20201201001
[Abstract](57) [FullText HTML](16) [PDF 0KB](11)
Abstract:
The landslide of expansive soil slope has the characteristics of long-term and recurrence, so the long-term stability of canal slope after reinforcement is still worthy of attention. In a long distance water diversion project, although the replacement measure for surface soil was adopted, the water vapor exchange between the expansive soil and the external environment was not completely blocked. After two years of operation, the obvious deformation occurred, and then measures of the umbrella anchor reinforcement and drainage hole layout were taken. Based on the monitoring data of the reinforced canal slope, the temporal and spatial deformation characteristics were analyzed by the HCPC method (hierarchical cluster analysis on principal component analysis). On this basis, the typical point was selected, the exponential smoothing method, the autoregressive moving average model and the multi factor nonlinear regression model were applied to analyze and predict the slope deformation. The results show that the deformation of the reinforced canal slope tended to be stable after nearly two months of adjustment, and was mainly affected by the external environment factors and fluctuates slightly at this stage. The deformation of the reinforced canal slope is inhomogenous in space, and the deformation range decreases to both sides with the original deformation body as the center. The canal slope deformation is mainly affected by time dependent effect, as well as rainfall, groundwater level and temperature. In view of the long-term repeated characteristics of expansive soil landslide, the follow-up observation should be strengthened.
doi: 10.12170/20210208004
[Abstract](13) [FullText HTML](4) [PDF 0KB](2)
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The Hechangzhou river reach is a typical braided reach and is one of the most violently changed reach in the lower reaches of the Yangtze River. After the impoundment of Three Gorges Dam, the sediment outflow decreased greatly, the new features of river bed evolution showed up and the navigation conditions changed accordingly in Hechangzhou braided recch. In order to restrain the scour development in the left branch and improve the navigation condition in the right branch channel, three underwater submerged dams in the left branch were successively built. Based on a large amount of measured data, the evolution characteristics of Hechangzhou braided reach were analyzed. Results show that the riverbed in the Liuwei reach continued to cut down in 2009, accompanied by occurrences with bank line collapse and development of central bar. The control effect of three submerged dams is significant, and the measured diversion ratio of left branch in 2019 was about 64%, 12% lower than that of the highest 76% in 2002. The riverbed in the right branch changed from slow deposition to general scour, and the navigation conditions were improved. However, the left branch has experienced a significant scour in local reach and two bank collapse events happened, which should be paid enough attention to.
doi: 10.12170/20201208002
[Abstract](1) [FullText HTML](0) [PDF 0KB](0)
Abstract:
The utilization of surface water resources is difficult in coastal areas due to short flow path and sharp gradient of river channel. Incorporating unconventional water resources such as reclaimed water and desalinated seawater into unified urban water systems in coastal cities is an effective way to alleviate water shortage. A key point to realize the unified allocation of conventional and unconventional water resources is to scientifically determine construction scales of unconventional water sources considering uncertainties of conventional water resources. In this paper, an optimal model for determining construction scales of desalinated seawater and reclaimed water considering inflow uncertainties is established through a case study in Weihai City. The non-dominated sorting genetic algorithm-Ⅱ is adopted to solve the model. Three indexes (reliability, resilience and vulnerability) are used to measure the performance of the whole water supply system and further compare results with the current basic scheme. The results indicate that at the planning level of 2030, the suitable construction scales of reclaimed water and desalinated seawater in Weihai urban area are 230 thousand m3/d and 150 thousand m3/d respectively. Based on these scales, the guarantee rate of urban water supply in Weihai urban area increases from 63.8% to 95.2%, and the average annual water supply cost is 660 million yuan. The results can provide decision-making reference for regional water supply planning.
doi: 10.12170/20201103002
[Abstract](4) [FullText HTML](2) [PDF 0KB](0)
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The prediction of runoff into the reservoir has important indications for the operation of Danjiangkou Reservoir and the utilization of water resources. Based on the gray wolf optimization algorithm (GWO), construct different prediction models, carry out the study of reservoir runoff prediction in Danjiangkou, discuss the selection of network structure hyperparameters, verify the characteristics of global traversability and fast convergence of GWO. The results show that the prediction accuracy and generalization performance of the GWO-LSTM model is better than that of the GWO-BP model and the stepwise regression model. The Nash efficiency coefficient of its verification period reached 0.969 on average. The overall trend forecast is good, and the peak capture is slightly insufficient, which is suitable for prediction of monthly inflow to the Danjiangkou reservoir; The prediction results of model hyperparameters based on empirical values are not as good as GWO. Based on empirical values, the NSE of the verification period is less than 0.5, which does not reach the acceptable range, and there is a certain contingency. It is recommended to select an optimization algorithm with global optimization characteristics for hyperparameter selection; The global traversability and fast convergence characteristics of the GWO algorithm are verified, and the convergence state can be reached after 3 iterations on average.
doi: 10.12170/20210416001
[Abstract](3) [FullText HTML](0) [PDF 0KB](0)
Abstract:
Large-scale hydraulic model tests can obtain similar phenomena closer to the prototype. This paper conducts experimental research on the overall large-scale landslide conditions that may occur in the near-dam reservoir area, and analyzes the generation, propagation and dissipation characteristics of surge caused by landslides in combination with a three-dimensional numerical model. The results show that the wave height and phase calculated by the numerical model are basically consistent with the experimental results. The type of surge in the reservoir area is a finite depth wave, and the wave energy is distributed along the depth of the water. The nonlinearity near the surge generation area is strong, and the wave height decays rapidly as it propagates; The superposition of surge at the dam abutment appears instantaneous surging. In the test, only weakly nonlinear oscillatory waves were observed in the near field waveform of surge waves. Under the experimental conditions, the impact kinetic energy conversion rate of the block model is about 2%-19%. The kinetic energy conversion rate of the slider is positively correlated with the relative volume and relative thickness, and negatively correlated with the Froude number. The low frequency wave is greatly affected by the topography, and the wave energy temporarily concentrates in the shallow water area of the bank slope, the spectral peak increases, and the high frequency wave increases with time. For narrow and deep valleys, surge waves are caused by large amount of landslides. Although the wave height is obviously weakened when the first wave energy is transmitted to the dam due to the influence of high and steep slope, the highest wave in front of the dam is usually formed by the reflection and superposition of surge waves, and the surge waves in the reservoir area are weak and slow. After the first wave arrives, there is still a risk that surge waves will overrun the dam body.
doi: 10.12170/20201014001
[Abstract](12) [FullText HTML](5) [PDF 0KB](1)
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Due to the long-term erosion of marine engineering by sea water, water molecules containing corrosive media infiltrate into concrete, making steel bars prone to chloride corrosion, causing structural expansion and cracking, which greatly reduces the service life of marine engineering. With the acceleration of marine engineering construction, the use of cement-based conductive composite materials for chlorine removal and corrosion protection has gradually received attention. Conductive composite materials were prepared by adding conductive materials into cement-based materials. Based on the study of mechanical properties and conductive properties of materials, this paper explored the effects of different dosages of polymer emulsion and conductive fillers, and cement-sand ratio on the dechlorination performance of materials. The influence mechanism of conductive fillers and polymer emulsion on the performance of materials was analyzed by SEM scanning analysis, and the mechanism of dechlorination and anticorrosion of materials was explored. The results show that the chloride ion content in the material can be significantly reduced by adding suitable conductive filler and polymer emulsion after 60 V DC piezoelectric infiltration for 180 min, and the chlorine removal efficiency is 84.24% higher than that of the specimen without conductive filler. The research results provide reference for reducing steel corrosion in marine concrete and improving service life.
doi: 10.12170/20210208002
[Abstract](3) [FullText HTML](2) [PDF 0KB](0)
Abstract:
The Yangtze River Channel is the main logistics channel of the Yangtze River shipping and an important link for regional economic coordination.At present, there are many researches on the relationship between transportation infrastructure and economic growth, but few literatures take the Yangtze River waterway as the research object to explore its influence on economic growth.Drew a causal diagram to qualitatively analyze the interaction between the Yangtze River waterway and the Yangtze River Economic belt, and to clarify the mechanism of the waterway construction promoting regional economic growth.Selected the time series data from 2005 to 2009, and used the extended C-D production function model to quantitatively calculate the economic contribution of investment in the Yangtze River waterway construction to the Yangtze River Economic Belt.On the whole, the contribution of economy shows an increasing trend year by year.The economic output of the Yangtze River Economic Belt increases by 1.74 percentage points for every 1 percentage point increase in the input for the construction of the Yangtze River waterway.The results show that the construction of the Yangtze River waterway plays a significant role in supporting the Yangtze River economy.In order to better facilitate the development of the Yangtze River Economic Belt, more investment should be put into the construction of the Yangtze River waterway in the future to improve its carrying capacity, and at the same time, more attention should be paid to scientific and technological innovation and ecological protection..
doi: 10.12170/20200710001
[Abstract](8) [FullText HTML](3) [PDF 0KB](0)
Abstract:
As a new type of foundation, the suction bucket foundation has good technical and economic performances compared with traditional foundations. The key construction parameter, soil plug, and construction efficiency are analyzed through model tests of a suction bucket foundation in silty clay with different suction pressure applied. Measured suction pressure in tests with different suction pressure applying patterns are between the required value and critical value calculated by the DNV standard. The suction pressure in suction releasing pattern is larger than that in suction maintaining pattern for suction bucket to reach the same depth. In addition, the least soil plug degree is obtained in the suction releasing pattern with a large suction pressure increment, provided penetration efficiency is assured. Theoretical analysis shows that the inside friction resistance increases with the gradient of inside pressure along depth and large friction resistance restricts the formation of soil plug. The mechanism of reduced soil plug in suction releasing pattern is explained by the excess pore water pressure results. The earth pressure results show that the normal effective stress mobilized on the bucket wall in the suction releasing pattern is larger than it in the suction maintaining pattern. Accordingly, the side friction mobilized of the former is also larger.
doi: 10.12170/20200519001
[Abstract](15) [FullText HTML](8) [PDF 1266KB](3)
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 county 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 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 the local area, especially coast regions of Yangtze River Delta Area, the ecosystem health index was 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.
doi: 10.12170/20190322001
[Abstract](322) [FullText HTML](159) [PDF 764KB](9)
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.
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2021, (3): 1-1.
[Abstract](31) [FullText HTML](15) [PDF 9488KB](18)
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2021, (3): 1-2.
[Abstract](24) [FullText HTML](15) [PDF 337KB](12)
Abstract:
2021, (3): 1-8.   doi: 10.12170/20210301004
[Abstract](64) [FullText HTML](19) [PDF 1074KB](21)
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Navigation tunnels are regarded as one of the effective ways to solve the layout problem of navigation buildings under the conditions of high mountains and valleys, and their section design is restricted by several factors. An objective optimization mathematical model for cross-sectional dimensions of large navigation tunnels is established in this study based on design passing capacity of navigation tunnels and critical ship speed. Section coefficients of navigation tunnels and tunnel widths are adopted as objective functions, while design passing capacity and critical ship speed are adopted as the constraints of the proposed model. And then, the multi-objective optimization problem of the proposed model can be transformed into a single-objective optimization problem according to the actual situation of engineering projects, and optimal solutions of objective functions can be solved based on the constraints. The proposed model is applied to the cross-sectional dimension analysis of the Goupitan navigation tunnel. The calculation results are in good agreement with the actual project, which verifies the rationality and effectiveness of the model.
2021, (3): 9-15.   doi: 10.12170/20200724002
[Abstract](25) [FullText HTML](6) [PDF 1229KB](5)
Abstract:
Concrete-filled steel tube rock-socketed piles are a new type of deep foundation in deep water and shallow overburden environments, and are widely used in the construction of deep water wharves in inland rivers. In view of the combined bearing characteristics of steel-concrete for concrete-filled steel-filled piles under cyclical horizontal loads such as ship impact force, wave force and current force, three models of large-scale concrete-filled steel tube rock-socketed piles of 1∶7.3 were made. At different heights of the pile body, strain measuring points were arranged on the outer side of the steel tube, the corresponding inner concrete block and the built-in stressed steel bars, with 18.0, 22.5 and 27.0 kN as the cyclic amplitude, to develop the steel-concrete joint bearing law of the concrete-filled steel tube rock-socketed piles test. The results show that the steel-concrete strain of the pile body satisfies the four stages of linear growth, steady fluctuation, severe vibration and sharp decline, and each stage accounts for 8.66%, 79.66%, 6.06% and 5.62% of the fatigue life; the strain of steel pipe on that outside the same pile section is quite different from that of concrete on the inside, and the maximum is more than 80% of the concrete strain. The built-in steel bars and the concrete always maintain strain coordination, and the maximum strain difference does not exceed 20% of the concrete strain; at the top of the pile with a small bending moment, the bending moment of pile body is mainly borne by inner concrete, which accounts for more than 70%. Along the pile, the ratio of the section bending moment borne by the steel pipe gradually increases. At the bottom of the pile, the proportion of the two bending moments is approximately equal. The steel pipe and the concrete are subjected to bending. Simultaneously, at the same pile section, the greater the cyclic amplitude, the earlier the two will reach the bending coordination state.
2021, (3): 16-24.   doi: 10.12170/20200524001
[Abstract](73) [FullText HTML](22) [PDF 1258KB](14)
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Water level plummet is one of the main external factors affecting the stability of bank slope, however, the existing calculation methods need to consider the seepage effect of water level drop on bank slope through the calculation of seepage force or pore water pressure or the coupling analysis of seepage field and stress field, which are complicated and inconvenient for engineering designers to adopt. In order to analyze the influence of water level plummet on the stability of bank slope conveniently, the stress state of one point in the bank slope with and without considering seepage force was analyzed, and an equivalent relationship that the influence of seepage force on bank slope stability could be seen as the decrease of the parameter of cohesion c was obtained. Combining this equivalent relationship with the strength reduction method, a simplified calculation model of bank slope stability was established, and then a simplified stability analysis method for bank slope stability under the influence of water level plummet was proposed. The homogeneous bank slope stability analyses were carried out by the simplified analysis method in this paper, the bank slope globally critical slip field (GCSF) method, Geostudio's Slope/W module method and the traditional ultimate equilibrium methods respectively, and the results show that the safe factors calculated by the above-mentioned methods are in good agreement, with the differences of 2.6%, 3.5% and 3.5% respectively. Then the heterogeneous bank slope stability analyses were carried out by the simplified analysis method in this paper and the slope globally critical slip field (GCSF) method respectively. The results show that the safe factors calculated by the two methods are also in good agreement, with the difference of 3.1%. It is indicated that the simplified calculation method proposed in this paper for homogeneous and heterogeneous bank slope stability analysis is reliable and feasible.
2021, (3): 25-30.   doi: 10.12170/20200521001
[Abstract](54) [FullText HTML](18) [PDF 836KB](12)
Abstract:
In order to investigate whether there is a unique correspondence between the relative humidity of 100% inside dam concrete and the pore water saturation of 100%, dam secondary concrete specimens with a water-binder ratio of 0.5 and different fly ash contents (0, 35%) were formed. The relative humidity inside the concrete specimens was monitored by temperature and humidity sensors and the pore water saturation of the concrete was calculated using a weighing test. The results show that the relative humidity inside the dam concrete with a water-binder ratio of 0.5 was kept at 100% in the insulation humidity state; however, the corresponding pore water saturation was not necessarily 100%; the pore water saturation of concrete without fly ash and with 35% fly ash was 85%~89% and 73%~76%, respectively. This indicates that 100% of the pore water saturation of the dam concrete corresponds to 100% of the internal relative humidity, and the internal relative humidity of 100% is not the only relative humidity corresponding to the pore water saturation of 100%. In the insulation humidity state, for concrete with a water-binder ratio of 0.5, the pore water saturation of concrete with 35% fly ash is less than that of concrete without fly ash.
2021, (3): 31-40.   doi: 10.12170/20200411001
[Abstract](32) [FullText HTML](8) [PDF 1595KB](1)
Abstract:
Through the rubber concrete three-point bending beam fracture test, the load, deflection and crack opening displacement values of the rubber concrete are measured, and the load-deflection curve and the load-crack opening displacement curve are drawn; according to "Hydraulic Concrete Fracture Test Regulations" and ASTM specifications, the fracture toughness and fracture energy are calculated, and the effect of different rubber contents on the fracture performance of concrete and the relationship between the cumulative energy of acoustic emission and fracture energy are studied; and the calculation results of the different fracture toughness calculation formulas given in the two codes are compared and analyzed. The test results show that the maximum load that the concrete can withstand after mixing with rubber is reduced, and the crack initiation toughness, unstable fracture toughness, fracture toughness, fracture energy and cumulative energy of acoustic emission are all reduced; the effective crack length and maximum deflection are the smallest when the rubber content is 10%, and increase when the rubber content is 20% and 30%; the ductility index gradually increases with the increase of the rubber content, and the maximum increase is 41%; and by fitting the fracture energy of concrete harmonic emission cumulative energy curve, the empirical formula in the form of \begin{document}$y=a+b{{\rm{e}}}^{cx}$\end{document} can be obtained. The ductility and deformability of the concrete are improved with the incorporation of rubber, the brittleness is improved and an empirical formula can be used to deduce the degree of damage to the concrete when a certain value of emitted energy is reached.
2021, (3): 41-49.   doi: 10.12170/20200520003
[Abstract](91) [FullText HTML](29) [PDF 4262KB](8)
Abstract:
As the deformation monitoring data of concrete dam has evident non-linear and non-stationary characteristics, and the data sequence contains a certain amount of noise, it is easy to lead to low accuracy predicted by the model. Aiming at the above issues, the deformation prediction model established for concrete dam, which is referred to as the complete ensemble empirical mode decomposition with adaptive noise (CEEMDAN) - permutation entropy (PE) - long short-term memory (LSTM), is proposed. Using the capability of CEEMDAN to adaptively decompose non-linear signals, this model decomposes original deformation data into a set of intrinsic mode functions (IMF) with different frequencies and obvious differences in complexity, which reduces the mutual influence of distinct scale information in the sequence. Then, the IMF quantities with similar complexity are combined and reorganized. Finally, LSTM models are respectively constructed for several re-organized sequences to perform prediction, and then the predicted results are added to obtain the final prediction. This study is based on modeling and analyzing the horizontal displacement monitoring data of a concrete dam. The results demonstrate that the CEEMDAN-PE-LSTM model shows significant improvement in accuracy compared to the conventional model, and is able to better predict nonlinear data sequence. As compared to the LSTM model, the mean average error (MAE), mean average percentage error (MAPE) and relative mean square error (RMSE) are reduced by 76.43%, 75.55% and 74.73%, respectively, suggesting that the proposed model can better exploit the variability of non-linear and non-stationary data by decomposing and reorganizing the original sequence to obtain distinct scale features with improved prediction accuracy, and can be effectively applied to the deformation prediction of concrete dams.
2021, (3): 50-58.   doi: 10.12170/20200804002
[Abstract](64) [FullText HTML](4) [PDF 1993KB](3)
Abstract:
The spudcan penetration and extraction processes of the jack-up drilling rig will seriously disturb the natural seabed. In the present study, the penetration and extraction processes of the jack-up platform in silty seabed were modeled with the help of an indoor physical model experiment, and comparison was made between the model findings and the field CPT repeated penetration results. Based on this, the disturbance effect of silty seabed caused by a single and repeated penetration and extraction of pile was discussed from a qualitative and quantitative perspective, respectively. The results show that compared with the initial spudcan penetration and extraction process, the geometric size of the pile pit caused by the second process was expanded to some extent; the excess pore water pressure caused by the second penetration of pile was lower than that created during the first pile penetration, and the maximum drop could reach 35%; the disturbance degree of seabed caused by the repeated penetration and extraction of pile generally decreased linearly with the increase of the horizontal distance from the center of the pile, and the soil at the middle layer was disturbed more seriously than shallow and deep soils; in comparison with the initial penetration, the tip resistance of pile during the second penetration reduced to some extent, while the corresponding final peak tip resistance was increased, together with the relatively close pulling forces between them; and the development trend of the pile tip resistance monitored from the indoor physical model experiment showed good consistency with the field CPT repeated penetration test results.
2021, (3): 59-66.   doi: 10.12170/20200611001
[Abstract](90) [FullText HTML](18) [PDF 8431KB](11)
Abstract:
The division of underground drinking water source protection areas in scientific and reasonable ways can prevent water sources from being polluted in the most precise ways and with a lower economic cost. The MODFLOW model was utilized to develop and calculate a simulation of the groundwater flow field of the Hutuo River groundwater source area in Shijiazhuang City. By utilizing the MODPATH, the 100 days and 1 000 days reverse migration trajectories of the tracer particles subjected to two different working conditions were calculated. The results were as follows: the average migration distances of the tracer particles at the end of 100 days under each of the two conditions were 0.54 km and 0.49 km; moreover, the average migration distance of each of the tracer particles at the end of 1 000 days was 6.1 km and 5.6 km. Also, the simulation considered the change of the groundwater flow field under the condition of utilizing the infiltration field. By analyzing the calculation results of these two working conditions, it was concluded that when the pumping wells inside of the water source area were generalized into the well groups, the specific trajectory geometry of the tracer particle reverse migration was more regular, and its migration distance was relatively short. At the same time, by considering the specific water supplement situation of the infiltration field, the whole infiltration field was included in the first-grade protection area as well.
2021, (3): 67-73.   doi: 10.12170/20200408001
[Abstract](196) [FullText HTML](28) [PDF 3143KB](24)
Abstract:
In order to reveal the natural background and spatial distribution pattern of drought-hatching environment in Shandong Province, the distribution of regional drought conditions in Shandong Province is divided by the method of GIS map cascade. Firstly, according to the causes of drought in Shandong Province, four drought factors, namely precipitation, soil moisture content, vegetation index NDVI and air temperature, were selected for GIS grid data processing to obtain corresponding drought factor layers. Then, the analytic hierarchy process (AHP) was used to determine the weight of each drought factor, and the four normalized drought factor layers were weighted and stacked to obtain a comprehensive drought factor map. Finally, the comprehensive drought factors diagram was overlayed with Shandong elevation distribution layer to get five drought areas of Shandong Province: the agricultural area in the northwest plain of Shandong Province is a heavy drought area, the southern part of northwest plain and Jiaolai plain are light arid regions, Shandong peninsula is a relatively humid wet area, the hilly and mountainous area in the south-central of Shandong Province and the southern Shandong coastal plain area are wet areas, and to put forward the suitable drought index of each partition. This study can provide technological support for drought monitoring and early warning in Shandong Province.
2021, (3): 74-83.   doi: 10.12170/20200412001
[Abstract](211) [FullText HTML](28) [PDF 1110KB](16)
Abstract:
Hebei Province is a region where high water demand and low water resources self-yield are extremely unmatched in China and even in the world. With the rapid economic development, it is particularly significant to optimize the allocation of regional water resources scientifically. In this study, Hejian County, located in Cangzhou, Hebei Province, was selected as the study area. Considering the constraint effect of two forbidden red lines of water use amount and water use efficiency, an optimal allocation model of water resources taking social and economic benefits as objective function was established. Then Artificial Fish Swarm Algorithm was employed to solve the model. The results indicate that the available water supply would be 107.28 million m3 in Hejian County and the water shortage rate would be as high as 50.8% in Longhuadian Town, and the water scarcity in each township would be mainly concentrated in agriculture in the planning year of 2025. The water use contradiction in various industries would be obviously improved after the optimal allocation of water resources. The achievements can provide key technical support for the fine management of water resources in Hejian County, and can also provide a reference for other counties in the north to optimize the allocation of water resources.
2021, (3): 84-95.   doi: 10.12170/20200416001
[Abstract](145) [FullText HTML](38) [PDF 1186KB](16)
Abstract:
With the intensification of climate change and human activities, water resources in the basin are more and more affected by the changing environment. It is of great significance to study the change characteristics of watershed water resources system and water demand prediction in the changing environment to support the management and rational allocation of watershed water resources. Based on the principle of system dynamics, coupled with the water demand prediction method considering physical mechanism, this article establishes the model of water resources system. Taking the Yellow River basin as an example, this paper analyzes the change characteristics of water resources system in the Yellow River basin under the action of multi-factor driving and multi-element stress, and predicts the evolution trend of water resources supply and demand in the Yellow River basin from 2017 to 2030 according to five different economic and social development situations in the future basin and the predicted future temperature and precipitation results using MPI climate model. The results show that: (1) The domestic water demand of the Yellow River basin increases continuously with the increase of the population and the per capita water demand of the basin. With the adjustment of industrial structure, the water demand for industry shows a trend of slow decrease, while the water demand for ecology and production increases year by year. (2) On the premise of strengthening the river basin water resources management and increasing the investment in water-saving technology, we should ensure the coordinated development of the basin economy and society, pay attention to the development of the economy while giving consideration to ecological environment protection in the basin, and meet the requirements of sustainable economic and social development in the next stage of the Yellow River basin. (3) In order to ensure the sustainable development of water resources in the Yellow River basin, and realize the ecological protection and high-quality development of the Yellow River basin, it is necessary to adjust the strategies of water resources management in the basin, improve the degree of water-saving, and promote the optimization of the industrial structure of the basin.
2021, (3): 96-102.   doi: 10.12170/20200608001
[Abstract](59) [FullText HTML](28) [PDF 1190KB](5)
Abstract:
According to the data of annual precipitation, annual average temperature of climatological stations and annual runoff of Tongjiezi Station in the Dadu River basin from 1951 to 2012, the Mann Kendall rank correlation test was used to identify the trend of annual runoff sequence, the periodic component was tested based on the wavelet analysis method, the sequential clustering method, the cumulative anomaly method and the Pettitt method were used to diagnose the change point, and the effect of climate changes and human activities on the annual runoff of the basin was revealed based on the comparison of the slope change rate of the cumulative amount. The results show that in the past 60 years, during 1951—1968, the annual runoff showed an insignificant decrease trend, the period of 1969—1987 showed an insignificant increase trend, the period of 1988—2012 showed an insignificant decrease trend, and the period of 1951—2012 showed an insignificant decrease trend; there were 7, 11, 17 and 28 years cycle components; in the past 60 years, change points of the annual runoff in the Dadu River basin were in 1968 and 1987; using 1951—1968 as the base period, during 1969—1987, the contribution rate of climate change and human beings activities to the reduction of annual runoff in the Dadu River basin was 36.22% and 63.78% respectively; during 1988—2012, the contribution rate of climate change and human activities to the reduction of annual runoff was 33.68% and 66.32% respectively; and in sum, human activities are the main factor and climate change is the secondary factor.
2021, (3): 103-110.   doi: 10.12170/20201013004
[Abstract](18) [FullText HTML](4) [PDF 3331KB](5)
Abstract:
The sea platform of Hangzhou Bay Sea-Crossing Bridge is near the center the bridge. The pier groups under the platform combined with ramp piers and main bridge piers compose complex bridge pier groups which induce significant scour around sea platform. In order to deeply understand the scour characteristics around the sea platform, based on field data, the scour characteristics around sea platform, the seabed evolution and minimum elevation of ramp piers were analyzed. In addition, the hydrodynamic characteristics around sea platform were also studied using numerical simulation. The research result shows that there is general scour in the region between upstream 500 m and downstream 1000 m, and in each side of the sea platform, there is local scour, whose maximum scour depth is nearly 14 m. The scour hole extends to the upstream region and induces some scours around ramp piers with considerable depths. In general, the scour depths of ZB and ZC ramp piers in upstream region are deeper than those of ZD and ZE ramp piers. This may be because the upstream ramp pier is affected not only by the sea platform but also by main bridge piers. The distribution of minimum scour elevation of each ramp pier has relationships with the distribution of spring tidal current.
2021, (3): 111-118.   doi: 10.12170/20201014002
[Abstract](33) [FullText HTML](4) [PDF 2057KB](5)
Abstract:
In this study, a total of 57 tests were performed to investigate the effects of three relative roughnesses (0.51, 0.86, 1.34) and six slopes (−0.02, −0.03, −0.04, −0.05, −0.07, −0.10) on the hydraulic characteristics of F-type jumps over adverse-sloped sinusoidal-corrugated beds, whose Froude Number ranged from 5 to 11. The experimental results show that compared to the classic hydraulic jump and the F-type jump on the smooth bed, the adverse-sloped sinusoidal-corrugated bed can effectively reduce the roller length and sequent depth ratio. And the rough bed is beneficial to stabilize the F-type jump. The velocity profiles are more sensitive to the relative roughness than the slope, and the relative roughness affects the similarity of these velocity profiles and the development of boundary layer thickness. The velocity profile is most uneven near 0.4 times roller length away from the initial point of the F-type jump. After 1.2 times the roller length, the momentum correction coefficient of the profile is almost 1.0. The shear force coefficient of the adverse-sloped corrugated bed is 10~16 times that of the horizontal-smooth bed, which indicates that the adverse-sloped sinusoidal-corrugated bed is very effective in energy dissipation over short distances.
2021, (3): 119-125.   doi: 10.12170/20200623001
[Abstract](60) [FullText HTML](11) [PDF 3346KB](9)
Abstract:
An effective emergency treatment for the pit collapse is vital to slow down the flow velocity of the pit pond and prevent the further development of the pit pond. The scheme of tree head-stone has been widely used in engineering application owing to its capacity of promoting siltation. The height and the spacing distance of the tree head-stone were generally determined by engineering experience, and these empirical values were short of theoretical and experimental basis. The arrangements of tree head-stone in pit collapse were tested using the physical model at Zhinan village, along the Yangzhong embankment of the Yangtze River. In this study, three heights and three spacing distances were orthogonally combined in the testing scheme, and the flow direction and velocity were measured at 12 locations using the three point method. Based on the analysis of the experimental results, the surface velocity was greatly affected by inertia, and the bottom velocity was dominantly controlled by the topography of riverbed. In comparison of the experiments with different heights and spacing distances, the mean flow velocity increased with the spacing distance of the stone, but decreased with the increasing height of the tree head. The resulting low flow velocity increased the possibility of siltation. Because the investment cost would increase with the height of tree head and the low spacing distance of stone, the best relative height of tree head and the spacing distance of stone were 0.15 and 6 m×6 m, respectively.
2021, (3): 126-135.   doi: 10.12170/0201120002
[Abstract](50) [FullText HTML](11) [PDF 889KB](4)
Abstract:
This study identifies risk factors associated with the utilization of mine water resources, and based on the objective of a bilateral coordination between supply and demand, selects three primary indicators, namely water volume, water quality, and economy (cost), and 12 secondary indicators of risk assessment to establish a risk assessment index system for mine water use. A mine water utilization risk assessment model is constructed on the basis of the set pair analysis (SPA) theory. Seven mining areas in the Xinghan area of the Jizhong coal base are selected as typical cases, and the analytic hierarchy process and SPA are applied to conduct mine water utilization risk assessment. The evaluation results of the two methods are consistent: Xingtai and Gequan have a low risk, whereas Zhangcun, Xiandewang, Xingdong, Dongpang, and Xipang have a medium risk. The risk level is mainly affected by water quality and volume, and is least affected by economy. The evaluation results are in line with the actual conditions of mine water resource utilization, thus confirming the feasibility of the SPA theory for mine water utilization risk assessment. The model can also be applied to risk assessment in other mining areas.
2021, (3): 136-143.   doi: 10.12170/20200830005
[Abstract](32) [FullText HTML](7) [PDF 2330KB](412)
Abstract:
At present, the research on the mechanism of vegetated slope mostly focuses on the mechanical effects rather than the hydrological effects of vegetation roots, and even there are some studies focusing on the hydrological effects, and most of them only focus on the water uptake and transpiration of single plant roots. In order to investigate the effect of plant spacing on hydraulic characteristics of the vegetated soil, such as the soil suction and water content at different depths, in multiple plants conditions and the drying-wetting processes, monitoring on the soil suction and water content at the observation points were carried out in the model tests composed of the vertical geotextile belts (water-retaining and reinforcement belts) and vegetation, in which the plant spacing was 20, 30 and 40 cm respectively. The model test results show that the maximum suction of the soil in the test with a plant spacing of 20 cm was 5.3% and 43.3% higher than that of the test group with a plant spacing of 30 cm and 40 cm respectively during the drying process. It can be concluded from the model test results that the smaller the plant spacing is, the more intense the water competition between plants, and the more obvious increase of suction in the soil. Within the root depth of vegetation, the suction and volumetric water content of the soil decrease with the depth of the soil, and the soil below the root depth is basically unaffected. Under the rainfall condition, rainwater preferentially infiltrates into the soil along the cracks, so the slope should be prevented from cracking. Since the vertical geotextile belts are installed on one or both sides of the plant root system, the plant spacing is actually the distance between the vertical geotextile belts. When the geotextile belts are used for slope protection, the distance between geotextile belts should not be too large, and they should be arranged under the principle of “fine and dense” in accordance with the cost and the spacing of plants.
2021, (3): 1-1.
[Abstract](19) [FullText HTML](15) [PDF 0KB](1)
Abstract:
2013, (6): 47-53.
[Abstract](1033) [PDF 1145KB](33)
2014, (3): 70-76.
[Abstract](3219) [PDF 1143KB](209)

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

Editor-in-Chief:Li Yun

PostCode:210024

Tel:025-85829135

Email:jnhri@nhri.cn

ISSN:1009-640X

CN:32-1613/TV

Postal Distributing Code: 28-19

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Publication Period: Bimonthly （1979 initial issiue）