三峡库区黄土坡滑坡滑带土直剪应力松弛特征试验研究

滑带土的应力松弛对滑坡的长期稳定性计算和支挡结构的设计具有重要的影响。为研究不同应力状态下滑带土的应力松弛特征,利用全自动直剪仪对三峡库区黄土坡滑坡滑带土在不同的垂直压力σ_n、剪应变γ、剪应变增量Δγ条件下进行了直剪应力松弛试验研究。结果表明:黄土坡滑坡滑带土的应力松弛曲线呈现出应变软化特征;随着垂直压力的增大,滑带土的应力松弛量逐渐增大;随着剪应变的增加,滑带土的应力松弛量呈先增加后减小的趋势;以滑带土应力松弛曲线的最大曲率点(T点)为分界点,可将滑带土的应力松弛过程划分为两个阶段;采用双指数衰减模型能够正确地描述滑带土直剪应力松弛曲线的特征;随着剪应变增量的增加,滑带土应力松弛双指数衰减模型拟合曲线拐点T出现的时间减小,滑带土第I松弛阶段应力松弛量的占比减小,与第II松弛阶段应力松弛量的占比呈轴对称关系,且到对称轴的距离减小。

Empirical Study on Stress Relaxation Characteristics of Sliding Zone Soil in Direct Shear Test on Huangtupo Landslide in the Three Gorges Reservoir Area

The stress relaxation of sliding zone soil has an important influence on the long-term stability calculation and design of retaining structurein landslide.In order to study the stress relaxation characteristic of sliding zone soil at different stress state,this paper carries out the stress relaxation tests of sliding zone soil of Hangtupo landslide in the Three Gorges Reservoir area with different vertical pressure σ_n,different shear strain and different shear strain increment using an automatic direct shear apparatus.The results show that the stress relaxation curves of direct shear stress in the sliding zone soil of Huangtupo slope landslide exhibit a strain softening feature.Before the peak value of shear stress,the steady stress relaxation increases gradually.The stress relaxation amount increases first and then decreases,and the stress relaxation ratio decreases gradually.After the peak value of shear stress,the steady stress relaxation is small and tends to be stable.There is a linear relationship between stress relaxation and normal pressure.The stress relaxation process is divided into two stages by taking the point T of maximum curvature of stress relaxation curve as dividing point.The double exponential decay model can describe the characteristics of the direct shear stress relaxation curve of sliding zone soil correctly.With the increase of shear strain increment,the time reaching point T decreases,and the proportion of stress relaxation in stage I decreases,and the proportion of stress relaxation of the sliding zone soil in stage I shows an axisymmetric relationship,and the distance from the symmetry axis decreases.