短时强降雨对排土场碎石土边坡稳定性的影响

Effect of short-term heavy rain on gravel soil slope stability of waste dump

为了研究排土场层状碎石土边坡在短时强降雨条件下的入渗过程及稳定性,首先在SEEP/W中进行降雨条件下的饱和-非饱和渗流分析,得到不同时刻的瞬态孔隙水压力分布,然后将SEEP/W模拟结果分别导入SIGMA/W和SLOPE/W,进行孔压-应力耦合分析和边坡稳定分析。最后通过对雨后不同时刻边坡内部孔隙水压力值变化情况的比较分析,探讨了雨后滑坡的发生机理。研究结果表明:强降雨对排土场碎石土边坡浅层影响最大,边坡浅层基质吸力随含水量的增大迅速降低,降低范围逐步向深部扩展,雨后基质吸力缓慢增大;降雨时排土场边坡渗流流速较大的区域主要集中在透水性最强的边坡浅层,当坡底存在弱透水层时,坡脚会很快产生涌水现象,涌水速度会逐渐增大,地下水位也会随之提高,雨后涌水减弱,地下水位降低;排土场边坡位移在降雨初期增加最快,之后增加速度趋缓,雨后会继续增大;降雨时排土场边坡安全系数快速下降,雨后随着边坡浅层水分继续下渗,边坡浅层下部含水量升高,最危险滑面位置会向基质吸力减小的边坡浅层下部发生转移,因此安全系数会继续降低至最小值,然后才开始缓慢增大。排土场层状碎石土边坡在短时强降雨作用下容易在雨后的一个较短时间内发生浅层滑坡。

In order to examine the effect of short-term heavy rain on stability of layered gravel soil slope of waste dump,firstly,saturated-unsaturated seepage analysis was carried out to obtain distribution of pore water pressure within the slope at different time using SEEP/W.Then distribution of pore water pressure within the slope was imported to SIGMA/W and SLOPE/W to carry out coupled stress-pore pressure analysis and slope stability analysis.At last,slope failure mechanism after rain was analyzed through the comparison of pore water pressure within the slope at different time after rain.The results show that surface of slope is most remarkably affected by heavy rain.The matric suction of surface of slope decreases rapidly from surface todeep slope along with the increase of water content.After rain,the matric suction of surface of slope increases rapidly first,and then increases with a relatively lower rate.Surface of slope has the largest seepage velocity due to its high permeability.If there exists a water-resisting layer in the bottom,water will come out of the slope from the slope toe with a rising flow rate and ground water level during the rain.The largest displacement increases rapidly first,and then increases with a decreasing rate during the rain and keeps increasing after the rain.The safety factor of slope decreases rapidly during the rain.After rain,the critical slip surface moves to the bottom of surface of slope,which has a lower matric suction due to water infiltration.Moreover,the safety factor of slope keeps going down to the minimum before it increases.It is most possible for the layered gravel soil slope of waste dump to fail shortly after short-term heavy rain.