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Stability evaluation and cracking research of steep loess slope under continuous rainfall
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摘要: 连续降雨导致边坡失稳破坏是黄土边坡常见的地质灾害之一。为了深入研究连续降雨对黄土陡坡渗流场、变形场及稳定性的影响，利用具有侧向隔渗和纵向减阻作用的隔离槽技术对黄土陡坡的两侧降雨边界进行处理，在此基础上开展黄土陡坡现场连续降雨（6 d）试验并进行数值模拟分析，描述了黄土陡坡开裂过程和特征，分析了坡体含水率和孔压响应，并探讨了裂缝对陡坡稳定性的影响。结果表明：边界隔离会导致连续降雨陡坡坡顶形成近乎横向贯通的裂缝，基本消除了局部降雨以外土体的边界约束效应；连续降雨后期陡坡开裂对坡体含水率及孔压分布产生较大影响，最大含水率及孔压中心以裂缝为竖向对称轴下移，并造成降雨结束4 d后水分总下渗深度为降雨期间的1.3倍；连续降雨导致陡坡的安全系数降低了58%，而降雨结束4 d后陡坡的安全系数提升了9%，降雨期间边坡开裂极易引发陡坡上半部滑坡。研究结果可为黄土地区边坡的降雨灾害防治提供参考。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.
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Key words:
- stability of slope /
- cracking failure /
- steep loess slope /
- isolation boundary /
- continuous rainfall
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图 4 土壤水分传感器布置（单位：m）
Figure 4. Diagram of moisture sensors and rainfall layout (unit: m)
图 11 数值计算中测点体积含水率变化曲线
Figure 11. Water content curve at measuring point in numerical calculation
图 13 数值计算中测点孔隙水压力变化曲线
Figure 13. Pore water pressure curve of slope at measuring point in numerical calculation
表 1 试验场地土的物性指标
Table 1. Physical property of soil at test site
天然含水率 / % 饱和度/% 干密度/(g·cm−3) 抗拉强度/kPa 液限/% 塑限/% 断裂能/(N·m−1) 8.93 25.51 1.32 5.32 26.43 16.42 3.84 压缩模量/MPa 渗透系数/(m·s−1) 湿陷系数 黏聚力/kPa 内摩擦角/° 天然 饱和 天然 饱和 18.05 5.72×10−6 0.11 16.315 9.050 26.62 23.93 
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