滑移孤石稳定性分析及失稳过程研究——以四川省马边县某孤石为例

Stability Analysis and Failure Process of Sliding Boulder——A Case Study in Mabian County, Sichuan Province

停留在高陡山坡且部分埋入土体的大体积独立崩积物——孤石,在降雨和地震等不良地质情况下会发生失稳破坏并威胁坡脚居民的生命财产安全,独立滑移破坏为孤石的一种主要破坏形式。为了探究独立滑移孤石的滑移力学原理,分析土体物理力学参数对孤石滑移失稳的影响。基于库伦土压力理论,建立上部楔形体土压力计算模型、下部楔形体模型和左右土体模型,使用Mathematics软件分析模型公式中的抗剪强度、黏聚力和滑裂角等对土压力的影响,并使用Flac3D有限差分法分析滑移孤石的失稳过程。结果显示,上部土体所提供的下滑推力随着抗剪强度和黏聚力值的增大而呈减小趋势,下部土体模型能承受的孤石最大推力约19 kN,当孤石推力大于19 kN时,孤石下部土体将以29.22°的滑裂角滑出;下部土体所提供的抗滑力随着抗剪强度和黏聚力的增大而增大,有限差分法模拟得到了孤石以推动表层土体向临空面滑移的方式失稳。孤石周围土体的抗剪强度和黏聚力对孤石稳定性具有控制作用,降雨使抗剪强度和黏聚力降低是孤石滑移失稳的主要原因。

The large-volume isolated collapsed material,which remains on the high and steep slopes and partially buries in the soil,may collapse and cause damage under unfavorable geological conditions such as rainfall and earthquakes,and threatens the safety of life and property of the residents at the foot of the slope.Isolated sliding is a major failure form of a separated stone.In order to explore the slide mechanism of the isolated rocks,the influence of soil physical and mechanical parameters on the stability of the boulders was analyzed.Based on Coulomb’s earth pressure theory,the upper wedge soil pressure calculation model,the lower wedge shape model and the left and right soil model were established.The influence of shear strength,cohesion and slip angle on the earth pressure was analyzed by using the Mathematical software.And the Flac3D finite difference software was employed to analyze the failure process of an isolated rock.As a result,the sliding thrust provided by the upper soil decreases with the increase of shear strength and cohesion.The maximum thrust of the isolated boulder that the lower soil can withstand is about 19 kN.The soil under the boulder will slide out at a slip angle of 29.22°when the thrust is greater than 19 kN.The anti-sliding force provided by the lower soil increases with the increase of shear strength and cohesion.The failure mode obtained by the finite difference simulation shows that the surface soil pushed by the boulder slides toward the free face.The shear strength and cohesion of the soil around the boulder have a controlling effect on the stability of the boulder.Rainfall,which reduces the shear strength and cohesion of the surrounding soil,is the main reason for the instability of the isolated boulders.