基于巴西圆盘数值试验的砂岩破裂过程分析

在PFC2D平台下设计了均质、含0.2 mm矿物颗粒和含0.2 mm孔隙砂岩的数值巴西圆盘试验。在试件左、右、中间、上部和下部设定了5个半径为5 mm的分析球。分别分析了试件加载过程中的x、y方向应力值。分析发现矿物颗粒的存在极大地增强了砂岩的力学行为,内部分析点x方向应力均高出其他情况x方向应力1～2个数量级,y方向应力则在同一个数量级上增加1～2倍。孔隙的存在弱化了砂岩力学行为,x、y方向应力均在同一数量级上减小1～2倍。说明外部监测到的应力变化与材料内部应力的变化情况有很大差异,这是物质约束与边界约束的不同造成的。

An Analysis of Fracture-Damage Process of Sandstone by Brazilian Disc Numerical Simulation Test

Three Brazilian disc numerical simulation samples of sandstone were established by PFC2D,they are homogeneous sample,samples containing dia.0.2 mm mineral grains and dia.0.2 mm pore.The 5 analytical circular areas with radius of 5 mm each are set up at the left,right,middle,upper and bottom of the test specimens,and the stress values at the x and y directions are analyzed in the loading process respectively.The analytical results indicate that the existence of mineral grains can greatly enhance the mechanical behaviors of sandstones.The stress in x direction at the inner analytical point is 10~100 times higher than the stress in x direction of other cases,and the stress in y direction increases 1~2 times as much as that in the same order of magnitude.The pore existence can weaken the mechanical behavior of sandstone,and the stresses in x and y directions in the same order of magnitude will decrease by 1~2 times as much.All these indicate that the stress changing monitored externally differs greatly from the internal stress changing in a material.This phenomenon is caused by the differences of material constraints and boundary constraints.