弱胶结泥质软岩的三向压缩损伤特性

针对西部矿区弱胶结软岩在复杂应力状态下的损伤行为,采用三轴压缩试验和等效应变原理,得到泥岩在三轴压缩下损伤变量的演化规律.基于weibull分布,引入修正系数λ建立可考虑泥岩残余阶段变形的统计损伤本构模型.结果分析表明：在三轴压缩下损伤变量呈先减小后增大的变化趋势,损伤演化过程没有水平段,表明受压时泥岩没有实际意义上的线弹性阶段；损伤变量减增变化的转折点恰好为全应力-应变曲线的屈服点和残余阶段起始点,说明该类泥岩的破坏起始于屈服点；当围压<3 MPa时,损伤起始点随围压增大而后移,当围压>3 MPa时,损伤初始点有前移的趋势,高围压下泥岩的峰前塑性提高,产生整体塑性剪切破坏；本构模型能够较准确地描述泥岩破坏的三阶段.

Damage behavior of weakly consolidated soft mudstone under tri-axial compression

In view of the damage behavior of weakly consolidated soft rock under complex stress state,the damage evolution law of mudstone under tri-axial compression was established firstly by employing the laboratory test and equivalent strain principle. Then, a statistical constitutive damage model was proposed based on Weibull distribution, in which a correction coefficient λ was introduced to describe the residue stage. The results show that the damage variable firstly decreases and reach the minimum when the loading stress arrive at yield point, and then increases sharply until to the residue stage. The sample has no actual linear elastic stage under tri-axial compression because there is no horizontal section during damage evolution process,and the failure process is launched at yield point and mainly produces in the second stage. When the confining pressure is less than 3MPa, the failure starting point is shifted forward with the increasing of confining pressure. However, it turns to the opposite when the confining pressure is greater than 3MPa which shows that the plastic behavior of mudstone before peak is enhanced and undergo overall plastic shear failure. The constitutive model could accurately describe the three deformation stages according to the test results.