基于物理模型试验的库水下降与暴雨作用下滑坡破坏机理研究

Model test of landslide of hanging rock wall under the action of reservoir water and rainstorm

摘要

【目的】三峡库区水位变化与降雨是滑坡发生的主要原因，为探究库区滑坡在库水下降与暴雨耦合作用下的变形与破坏机理。【方法】以吊岩壁滑坡为原型构建1:87缩尺物理模型，通过布设孔隙水压力、土压力以及位移传感器来监测滑坡内部应力变化以及变形过程。设置5种工况，进行两阶段加载试验，结合岩土体数值模拟软件建模，通过极限平衡法构建吊岩壁滑坡稳定性评价模型。【结果】结果显示：暴雨诱发滑坡滑体孔隙水压力增幅达到126.7%,显著高于单一水位骤降工况下的水压力值；土压力在滑坡不同位置呈现不同变化，前缘水位骤降导致土压力值由3.5 kPa降至2.84 kPa,中上部暴雨荷载的施加引发土压力值由2.02 kPa增至2.83 kPa;位移监测显示工况5累计位移量达到0.848 m,是单一水位工况下的5.65倍；根据数值模拟结果，通过贡献度计算得出库水位下降对稳定性的影响比重为48.6%,暴雨作用对稳定性的影响比重为51.4%。【结论】结果表明：库水位骤降主导滑坡稳定性劣化，通过渗透压力梯度诱发前缘牵引破坏；暴雨作用加剧滑带软化，驱动后缘推挤变形。二者耦合产生链式破坏效应，“175 m降至145 m水位骤降+暴雨”工况安全系数降幅达8.1%,为最不利工况。

Abstract

[Objective] Water level fluctuations in the Three Gorges Reservoir area and rainfall are recognized as major triggers of landslides. To investigate the deformation and failure mechanisms of reservoir landslides under the coupled effects of reservoir drawdown and heavy rainfall, [Methods] a 1:87 scaled physical model of the Diaoyanbi landslide was constructed. Changes in internal stress and deformation processes within the landslide were detected using pore water pressure sensors, soil pressure sensors, and displacement sensors. Five scenarios were designed, and a two-stage loading test was conducted, combined with numerical modeling using geotechnical simulation software. A stability evaluation model for the Diaoyanbi landslide was established based on the limit equilibrium method. [Results] The result indicated that heavy rainfall increased the pore water pressure within the sliding body by 126.7%, significantly exceeding the water pressure under single rapid drawdown scenarios. Soil pressure exhibited varying changes across different positions of the landslide; at the front edge, rapid water drawdown reduced the soil pressure from 3.5 kPa to 2.84 kPa, while in the middle-upper section, rainfall loading increased the soil pressure from 2.02 kPa to 2.83 kPa. Displacement monitoring revealed that cumulative displacement under Scenario 5 reached 0.848 m, 5.65 times greater than that of the single water drawdown scenario. Numerical simulations showed that the influence of reservoir drawdown on stability accounted for 48.6%, while the impact of heavy rainfall accounted for 51.4%. [Conclusion] The findings demonstrated that rapid reservoir drawdown predominantly deteriorates landslide stability, inducing frontal traction failure through the gradient of seepage pressure, while rainfall intensifies shear band softening and drives rear-edge push deformation. The coupling of these factors produces a chain failure effect, with the safety factor under the “175 m to 145 m water level drawdown + heavy rainfall” scenario decreasing by 8.1%, representing the most adverse condition.

关键词

吊岩壁滑坡 / 孔隙水压力 / 库水位骤降 / 暴雨耦合 / 模型试验 / 数值模拟 / 渐进破坏 / 降雨

Key words

Diaoyanbi landslide / pore water pressure / rapid reservoir drawdown / rainfall coupling / model test / numerical simulation / progressive failure / rainfall

基金资助

国家自然科学基金项目(59035679)

2002 年高等学校博士学科点专项科研项目(20020183061)