土石混合体直剪试验的破坏特征及抗剪强度取值方法研究

摘要

In direct shear tests of earth-rock aggregate,empirical method is always adopted to determine shear strengths,while less considering the variation characteristics of shear stress-shear displacement relationship curves and failure characteristics of shear plane. Based on this,big earth-rock aggregate samples with different moisture contents are collected from typical earth-rock aggregate bank slope in Three Gorges Reservoir area to carry out the indoor direct shear test. The test emphatically analyzes the variation characteristics of shear stress-shear displacement relationship curve,failure characteristics of shear plane,and shear leap phenomenon. Meanwhile, an analytical method,using critical plastic shear strength and ultimate shear strength to determine the earth-rock aggregate shear strength , is put forward. With physical significance , the method can reflect structural characteristics of earth-rock aggregate better than conventional method,and can provide reference for engineering design.%在土石混合体直剪试验中，抗剪强度值的确定往往采用经验方法，较少考虑试验过程中剪应力-剪切位移关系曲线变化特征和剪切面破坏特征。基于此，特选取三峡库区典型土石混合体库岸边坡，现场采集试样，进行不同含水率的土石混合体大试样室内直剪试验，重点对剪应力-剪切位移关系曲线变化特征、剪切面破坏特征以及直剪试验中的剪切“跳跃”进行详细分析，并提出用临塑抗剪强度和极限抗剪强度来分析土石混合体的抗剪强度的方法。该方法具有较好的物理意义，比常规的取值方法更能反映土石混合体特殊的结构特征，值得工程设计计算参考借鉴。