降雨优势入渗通道对古滑坡复活的影响

Influence of rainfall preponderance infiltration path on reactivation of ancient landslides

水是导致古滑坡复活的重要因素,裂缝可加剧降雨优势入渗,二者的耦合作用是促进古滑坡复活的本质原因。在古滑坡复活案例调查的基础上,采用离心机物理模型试验表明,古滑坡体的渗透性一般较弱,常规降雨很难入渗至深部并促发较大规模滑坡复活;当滑坡表层出现裂缝并逐渐向下扩展时,古滑坡发生大规模复活的可能性显著增大。采用数值模拟方法分析降雨条件下裂缝的深度、位置和数量对古滑坡复活的影响,结果表明:随裂缝深度的增加,渗流影响范围越来越大,雨水到达滑带的时间也越来越短。当裂缝位于滑坡体后部时,滑坡体易沿古滑带发生推移式复活;当裂缝位于滑坡体前部时,易发生渐进后退式复活,且所需降雨时间更短。随着裂缝数量增加,滑体内渗流场影响范围扩大、饱和时间明显缩短,相应地加剧古滑坡复活。因此,及时处理古滑坡表面出现的裂缝是有效阻止古滑坡复活灾害的关键。

Water is one of important factors leading to the reactivation of ancient landslides,and cracks can intensify rainfall infiltration. The coupling effect of water and cracks is the essential reason to promote the reactivation of ancient landslides. Based on studying lots of ancient landslide reactivation cases,the centrifuge physical model tests were carried out. The experiment results show that the permeability of ancient landslides is so weak that it is difficult for regular rainfall to infiltrate into the deep site of landslides,which cannot easily induce the reactivation of large-scale landslides. When cracks appear on the landslide surface and gradually expand downward,the reactivation possibility of ancient landslides in a large scale increases significantly. Furthermore,numerical simulation is performed to analyze the influence of the depth,location and number of cracks on the reactivation of ancient landslides under rainfall conditions. The results indicate that with increasing the crack depth,the influence range of seepage is larger and larger,and the time for rainwater to reach the sliding zone is shorter and shorter. When the crack is located at the rear of the landslide,the landslide is easy to reactivate with a push type along the ancient sliding zone. When the crack is located at the front of the landslide,it is easy to promote the occurrence of progressive reactivation from the front edge to the rear edge,and the required rainfall time is shorter. With increasing the number of cracks,the influence range of the seepage field in the landslide body is enlarged and the saturation time is shortened obviously,which aggravates the reactivation of the ancient landslide. It is suggested that timely treatment of the cracks in the ancient landslides is the key to effectively prevent the reactivation of ancient landslides.