连续降雨条件下某震后高边坡稳定性分析

基于饱和-非饱和渗流理论,综合考虑降雨入渗引起土体重量增加、渗透力增大以及抗剪强度降低等因素的影响,建立降雨条件下震后高边坡有限元模型,运用自编计算程序USLOPE-FEM进行稳定性分析。研究结果表明:未降雨之前,坡体塑性应变主要集中分布于松散堆积体下部与基岩分界面,边坡已经接近临界平衡状态;降雨量20mm/h时连续入渗使边坡上部土层含水量增加,负压区消失且出现饱和区;随着降雨时间延长,坡体表层暂态饱和区逐渐向内部推移,土体的重量和渗透力显著增大、抗剪强度明显降低,坡体中剪应力整体增大,塑性应变区向坡顶扩展而逐渐贯通;连续降雨6h后,临空面表层出现局部滑塌,连续降雨36h后整个堆积层将沿基岩滑塌逐步堵江。研究成果可为强降雨条件下边坡安全性评价提供参考,也为该边坡的失稳预警与滑坡防治积累资料。

Stability Analysis of Post-earthquake High Slope under Continuous Rainfall

Continuous rainfall is an important factor inducing slope failure,and the causes of saturated-unsaturated slope failure under strong rainfall infiltration are diverse and complex.However,current research on the combined effects that induce slope failure is inadequate,particularly in relation to the increase in soil weight and softening of strength parameters after rainfall infiltration,both of which can impact slope stability.In this study,we establish a finite element model of a high slope following the Wenchuan earthquake in the condition of continuous rainfall.In the modeling process,the factors affecting slope stability caused by rainfall infiltration are considered,such as soil weight increase,penetration increase,and shear strength decrease.Furthermore,to analyze slop stability we employ a self-compiled calculation program,USLOPE-FEM,which is based on saturated-unsaturated seepage theory.Results show that the plastic strain zone of the slope is mainly distributed in the interface between the bottom of loosely accumulated materials and bedrock,and that the slope was close to a critical state of equilibrium before the rain.However,when the rainfall reached 20 mm/h,continuous infiltration increased the soil water content in the upper slope,the area of negative pressure disappeared,and a zone of saturated zone appeared.With continuation of rainfall,the transient saturated zone on the slope surface gradually developed towards the interior,causing a dramatic increase of in the weight and penetration of the slope soil,together with an evident decrease in shear strength.Furthermore,an integral increase of shear stress in the slope occurred and the plastic strain zone extended and interpenetrated gradually to the top of slope. After six hours of continuous rain,a local slump appeared on the surface of the free face,and after 36 hours the whole accumulation horizon gradually slumped along the bedrock and block river.Based on results of calculations and the above analysis,it is recommended that the slope is firstly improved and strengthened in relation to instability during continuous rainfall.It is considered that the results of this study can be used as a reference for evaluating slope safety under heavy rainfall.