Experimental Study on Instability Characteristic and Bearing Capacity of Slope with Bedrock under Rainfall
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摘要:
为了研究降雨诱导基覆型边坡失稳特性，采用室内模型试验方法对基覆型边坡在暴雨作用下的失稳过程及机制进行了系统研究. 通过探讨降雨前后边坡内土体含水率和孔隙水压力在时间、空间上的变化特性，揭示降雨诱导的边坡失稳机制. 同时通过坡顶加载方法研究了雨后边坡承载力变化规律. 研究结果表明：随着降雨的发展，在坡脚处首先出现土体液化流动现象，随后出现土体局部脱落；随着降雨的持续进行，土体脱落破坏的范围逐渐增大，进而导致上方土体临空面加大，土体破坏后随即被雨水饱和软化而向下滑动，后方土体进一步被侵蚀，最终造成了一定深度和宽度的边坡破坏现象；边坡内土体含水率升高与孔隙水压力的增大是导致边坡失稳破坏的主要因素；降雨停止后，边坡可以承受的极限荷载先增大后减小，最后趋于稳定，而基覆型边坡在顶部静荷载作用下破坏模式呈现出整体和局部滑移模式.
Abstract:In order to investigate the characteristics of slope with bedrock induced by rainfall, the failure process and mechanism of slope with bedrock under rainstorm were studied systematically by laboratory model test. The variation characteristics of soil moisture content and pore water pressure in time and space before and after rainfall were discussed to reveal the mechanism of slope instability induced by rainfall. Besides, the variation law of slope bearing capacity after rain was studied by loading at the top of slope. The results show that with the development of rainfall, the liquefaction flow of soil appears first at the foot of the slope, and then the local shedding of the soil occurs there. With the continuous rainfall, the scope of soil shedding damage gradually increases, which leads to the increase of the free surface of the upper soil. After the soil is damaged, it is saturated and softened by the rain and slides downward, and the rear soil is further eroded, resulting in the slope failure of a certain depth and width. The increase of soil moisture content and pore water pressure in the slope are the main factors leading to the instability and failure of the slope. After the rainfall stops, the ultimate load that the slope can bear increases at first and then decreases, and finally tends to be stable, while the failure of the slope with bedrock shows either a global slip mode or a local slip mode under the top static load.
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Key words:
- slope with bedrock /
- rainfall /
- failure characteristic /
- bearing capacity
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图 3 砂土表观黏聚力和内摩擦角随饱和度变化曲线
Figure 3. Variation of sand cohesion and sand internal with saturation
图 8 孔隙水压力与体积含水率随时间变化曲线
Figure 8. Variations of pore water pressure and water content with time
图 9 边坡内体积含水率不同时间的空间分布
Figure 9. Spatial distribution of moisture content in slope at different time
图 10 边坡内孔隙水压力不同时刻的空间分布
Figure 10. Spatial distribution of pore water pressure in slope at different times
图 14 边坡顶部极限载荷随雨停后时间的变化
Figure 14. Variation of ultimate load with time after rain stop
表 1 各物理量的相似关系
Table 1. Similarity law of each physical quantity
物理量 相似常数 物理量 相似常数 H CH c Cc=CγCH γ Cγ ϕ 1 g Cg $ \mathrm{\nu } $ 1 $ \beta $ 1 Ir ${C_{I{\rm{r}}}} = C_H^{0.5}C_g^{0.5} $ $ \alpha $ 1 k ${C_k} = C_H^{0.5}C_g^{0.5} $ z CH t ${C_t} = C_H^{0.5}C_g^{-0.5} $ θ1 1 q ${C_q} = {C_\gamma }{C_H} $ θ2 1 
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表 2 不同质量含水率条件下的强度指标
Table 2. Strength index under different water moistures
质量含水率/% 饱和度/% c/kPa $\phi $/ （°） 0 0 0 35.89 6 25.75 2.71 32.59 12 51.50 6.09 31.15 18 77.25 6.15 30.98 23 100.00 1.16 29.88
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表 3 边坡降雨试验设计
Table 3. Design of slope rain test
工况
编号降雨持续
时间/h降雨强度/
（mm•h–1）降雨
等级雨停后加
载时间/h1 4.5 21.96 暴雨 0 2 4.5 21.96 暴雨 5 3 4.5 21.96 暴雨 10 4 4.5 21.96 暴雨 20 5 4.5 21.96 暴雨 40 6 4.5 21.96 暴雨 无加载
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表 4 不同含水率下边坡安全系数理论值
Table 4. Safety factor of slope under different water moistures
质量含水率/% 饱和度/% 安全系数 0 0 < 0.10 6 25.75 1.80 12 51.50 3.70 18 77.25 4.20 23 100.00 0.85
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