软化Mohr-Coulomb材料强度参数的测定方法

为了得到试件的粘聚力和内摩擦角随轴向塑性压应变变化的曲线提出本方法。试件的弹塑性本构关系遵循相关联的Mohr-Coulomb强度准则;对常规三轴试验,试件受力进入塑性状态后,处在棱椎状屈服面的棱上,加载过程遵循Koiter流动法则。按经典塑性力学理论,推导得到轴向塑性压应变与轴向应力与轴向应变的关系;在常规三轴试验机上获得不同围压下试件的全程应力-应变曲线,进而可得到各自围压下轴向塑性压应变随加载过程的变化曲线;把来自不同围压下对应同一轴向塑性压应变的应力分别代入屈服面方程,即可求得对应的粘聚力和内摩擦角。结果表明,Mohr-Coulomb材料的两个强度参数的变化由轴向塑性压应变确定。轴向塑性压应变可以作为塑性变形的状态参数,它和试件的受力过程可以唯一确定试件的变形过程。

Strength Parameter Measuring Method for Softening Mohr-Coulomb Material

The purpose of this method is to obtain the curve describing the relations among specimen's cohesion, internal friction angle and the axial plastic pressure strain variation. The elastoplastic constitutive relation of specimen follows associated Mohr-Coulomb strength criterion. In conventional triaxial test, specimen's stress in plastic state is on an edge of pyramid shaped yield surface. The loading process follows the Koiter flow rule. According to the classical theory of plastic mechanics, the relations among the axial plastic compressive strain, axial stress and axial strain were derived. Complete stress-strain curves under different confining pressures were obtained by using conventional triaxial test machine. Then the curves related axial plastic pressure strain and loading process under respective confining pressures were obtained. For a given axial plastic pressure strain, there is a defined stress corresponding to every confining pressure. Thus, the cohesion and internal friction angle for every given axial plastic pressure strain were obtained. Results show that the variation of two strength parameters of Mohr-Coulomb materials is determined by the axial plastic strain. Axial plastic pressure strain can be used as a parameter of plastic deformation. Axial plastic pressure strain and loading process of specimen can uniquely determine its deformation process.