降雨触发不同级配堆积体滑坡模型试验研究

Model tests on rainfall-induced colluvium landslides: effects of particle-size distribution

深入研究降雨条件下堆积体坡失稳规律对滑坡预测预报和防灾减灾具有重要的理论意义和工程实用价值。开发研制了降雨滑坡室内模型试验系统,对3种配制的堆积体土样进行了模型试验。研究了降雨条件下堆积体土坡的渗流、变形、破坏和颗粒运移的规律,探讨颗粒级配对堆积体土坡稳定性的影响。结果表明:坡内土体体积含水率、孔隙水压力和吸力随降雨历程响应明确;湿润锋到达后体积含水率和孔隙水压力持续增加而吸力持续减小,达到峰值后稳定;降雨停止后体积含水率和孔隙水压力立即降低而吸力逐渐增大。坡体破坏瞬时土体位移有一个加速过程。颗粒级配(含石量)对土坡破坏模式具有显著的影响;堆积体含石量为13%,19%,41%的土坡破坏模式分别为多级后退式破坏、冲蚀引起的局部浅层滑动破坏和块状滑动破坏;含石量越小,滑裂面越明显;含石量对细颗粒流失也有影响,含石量越大细颗粒流失越显著,坡脚细颗粒含量越大。

Investigation of the mechanism of rainfall-induced colluvium landslides and a reliable evaluation method for the colluvium slopes are essentially important for theoretical researches and practical projects. A fully instrumented laboratory model test system for rainfall-induced landslides is developed. Three model tests are conducted for three types of granular soils to investigate the seepage, deformation and particles migration of loose colluvium soil slopes under rainfall conditions, and the effects of particle-size distribution on infiltration and slope stability of colluvium slopes are discussed. The results show that the volumetric water content, pore water pressure and soil suction in the slope vary with rainfall infiltration. When the wetting front reaches the corresponding measuring point, the volumetric water content and pore water pressure continue to increase while the suction continues to decrease with time. After some time, the measured values become stable. Once the rain stops, the pore water pressure and water content response immediately and gradually decrease, while the soil suction in the slope gradually increases. The displacement of the slope is accelerated when a failure occurs. The initial particle-size distribution, e.g., the content of stone, has a significant impact on the failure modes. The failure modes for the three slopes, which are composed of colluvium soils with stone content of 13%, 19% and 41%, respectively, are multi-level retrogressive sliding failure, shallow sliding failure, massive sliding failure, correspondingly. With a smaller stone content, the slip surface is deeper. The transport of fine particles is more remarkable and the content of fine particles near the toe of a slope is greater when the stone content increases.