膨胀土边坡非饱和渗流及渐进性破坏耦合分析

A coupling analysis of unsaturated seepage and progressive failure of an expansive soil slope

膨胀土边坡受降雨影响产生膨胀变形,是典型的非饱和土多场耦合问题。为探究降雨入渗对其渐进性破坏的失稳过程,基于饱和-非饱和渗流理论、膨胀土弹塑性本构关系和应变软化理论,利用应变软化模型、FLAC3D二次开发平台和内置FISH语言,提出了一种综合考虑非饱和渗流、膨胀变形和应变软化的多场耦合数值分析法。结合工程实例,通过该方法探讨了降雨入渗条件下膨胀土边坡非饱和渗流、位移响应及渐进性破坏的变化规律。结果表明:膨胀变形和应变软化受控于非饱和渗流的时空分布,对边坡位移响应过程影响显著,也易导致饱和-非饱和分界带形成剪应力集中区。膨胀土边坡渐进性破坏由局部破坏转变为整体性失稳,其塑性破坏区首先随悬挂型暂态饱和区的变化向坡内扩展,雨后逐渐形成第二条由坡脚向坡顶扩展的滑动带,呈现出多重滑动性和后退牵引式的破坏特征。

Expansive deformation of expansive soil slopes caused by rainfall is a typical multi-field coupling problem of unsaturated soils.The instability process of the gradual destruction of rainfall infiltration is investigated in this paper.Based on the saturated-unsaturated seepage theory,the elastoplastic constitutive relationship of expansive soil and strain softening theory,train softening model,FLAC3D secondary development platform and built-in FISH language are adopted,and a multi-field coupled numerical analysis method considering unsaturated seepage,expansion deformation and strain softening is proposed.Combined with engineering examples,this method is used to explore the law of unsaturated seepage,displacement response and progressive failure of expansive soil slopes under rainfall infiltration.The results show that the expansion deformation and strain softening are controlled by the spatiotemporal distribution of unsaturated seepage,which has a significant effect on the slope displacement response process,and it also easily causes the saturated-unsaturated boundary to form a shear stress concentration zone.The progressive failure of the expansive soil slope changes from local failure to overall instability.The plastic failure area of the expansive soil slope first expands into the slope with the change of the suspension-type transient saturation zone.After the rain,it gradually forms a second sliding belt extending from the foot of the slope to the top of the slope,showing the multiple sliding characteristics and backward traction-type failure.