基于环剪试验的黄土滑坡失稳机理研究

Study on instability mechanism of loess landslide based on ring shear test

黄土滑坡启动变形受到外界因素影响显著,宏观上表现为累积位移-时间曲线呈不同形式增长特征。为了研究不同应力水平下黄土滑坡的剪切变形特性和变形机理,文中开展了不同剪应力条件和不同初始剪应力条件下的非饱和黄土环剪试验。试验结果表明:阶跃型滑坡变形过程中,衰减蠕变阶段的变形量呈现逐渐增加趋势,土体由衰减蠕变形态逐渐过渡到非衰减蠕变形态,在达到启动临界应力后呈现出突变状态,具有明显的"触变性"。直线型滑坡变形过程中,土体剪切位移速率和抗剪强度表现出明显的正速率效应;随着剪切位移增加,土体由应变软化特征逐渐转变为应变硬化。结合实例验证了滑坡始终处于"自我调整"状态,外界因素导致滑坡呈现出不同变形行为,试验结果可为黄土滑坡预测预报提供参考。

The initial deformation of loess landslide is significantly affected by external factors.Macroscopically,the cumulative displacement time curve increases in different forms.In order to study the shear deformation characteristics and mechanism of loess landslide under different stress,ring shear tests of unsaturated loess under different shear stress and different initial shear stress were carried out.The results show that the deformation in attenuated creep stage gradually increases and the soil changes from attenuated creep to non-attenuated creep during step landslide deformation process.A sudden change occurs after reaching the critical start-up stress,which has obvious“thixotropy”.In the process of linear landslide deformation,the shear displacement rate and shear strength of soil show an obvious positive rate effect.Meanwhile,the soil gradually changes from strain softening to strain hardening with the increase of shear displacement.It is verified with examples that the landslide is always in a“self-adjusting”state,and external factors have caused the landslide to show different deformation behaviors.Therefore,the results can provide reference for the prediction of loess landslide.