降雨作用下生态边坡客土稳定性研究

Analysis on stability of borrowed soil in ecological slope under rainfall effect

生态边坡客土的破坏具有沿土-岩界面滑移的特性,针对这类浅层边坡,Mohr-Coulomb理论不能较好地描述低应力水平的破坏特征。而且,在降雨条件下,边坡湿润峰抵达土-岩界面后,界面抗剪强度与客土入渗速率迅速降低,坡面径流剪切力迅速增大。为了研究降雨作用下生态边坡客土稳定性,建立了描述界面破坏特征的剪切应力-位移模型,在此基础上,结合GA模型和质量守恒定律,考虑降雨入渗-径流过程的影响,对降雨过程中客土极限状态进行分析,得到客土容许位移变化规律。研究结果表明:降雨过程中,客土容许位移具有平稳-逐渐减小-平稳的三段式变化规律;降雨初期,入渗水重力与坡面水流剪切力的综合作用增大了下滑力,容许位移值由稳定阶段进入逐渐减小阶段;降雨后期,入渗水抵达土-岩界面,界面抗剪强度迅速减小,容许位移值降至最小值。

The failure of the borrowed soil of ecological slope has the characteristics of sliding along the soil-rock interface,and then the low stress level failure characteristics of this kind of shallow slope cannot be well described by Mohr-Coulomb theory.Moreover,under the condition of rainfall,the interface shear strength and the infiltration rate of the borrowed soil rapidly decrease along with the rapid increase of the slope runoff shear stress after the slope wetting front reaching the soil-rock interface.In order to study the stability of the borrowed soil of ecological slope under the rainfall effect,a shear stress-displacement model for describing the interface failure characteristics is established.On the basis of this,the rainfall infiltration-runoff process is considered in combination with GA(Green-Ampt)model and the law of energy conservation,and then the ultimate state of the borrowed soil during rainfall is analyzed,while the changing law of allowable displacement is obtained as well.The study result shows that the allowable displacement of the borrowed soil has a changing law of three-stages,i.e.steady—gradually decreasing—steady during rainfall.In the early stage of rainfall,the downwards sliding force is to be increased by the comprehensive effect of both the infiltrated water gravity and the slope flow shear stress along with the allowable displacement coming from the steady stage into the gradually decreasing stage,while the interface shear strength is to be rapidly decreased and the allowable displacement is to be lowered to its minimum value when the infiltrated water reaches the soil-rock interface in the late stage of rainfall.