不同角度充填节理花岗岩剪切裂纹扩展规律及断裂机制研究

Shear crack propagation laws and fracture mechanism of filled joint granite with different angles

增强型地热系统储层中岩体节理通常含有充填物,充填节理的剪切力学行为直接影响储层渗透性及连通性。基于不同角度充填节理花岗岩直剪试验,研究了充填节理花岗岩剪切破坏的力学特性、损伤变量演化及裂纹扩展规律。结果表明:充填物及节理角度影响花岗岩抗剪强度,表现为充填物改变裂纹扩展介质,节理角度影响花岗岩剪切时节理面的受力状态;充填节理花岗岩损伤破坏过程分为裂纹闭合、裂纹萌生发育、裂纹扩展破坏3个阶段,损伤变量随着损伤过程进行呈不断增大趋势;节理花岗岩剪切裂纹扩展方向可分为水平方向及平行节理方向,0°与90°节理试件剪切裂纹沿水平方向扩展直至贯通试件,30°、45°与60°节理试件剪切裂纹扩展方向与自身节理角度一致。

In enhanced geothermal systems(EGS)reservoirs,rock fractures in the form of filled joints often contain fillings,and the shear mechanical behavior of filled joints directly affects the permeability and connectivity of the reservoir.Based on direct shear tests on filled joint granite with different angles,this study investigates the mechanical characteristics of shear failure,evolution of damage variables,and crack propagation laws of granite with filled joints.The results indicate that the filling material and joint angle affect the shear strength of granite.The filling material alters the medium for crack propagation while the joint angle affects the stress state of the joint surface during shear.The process of damage and failure in granite with filled joints can be divided into three stages:crack closure,crack initiation and development,and crack propagation and failure.The damage variable increases continuously as the stages progress.The direction of shear crack propagation in jointed granite can be classified into horizontal direction and parallel-to-the joint direction.For specimens with joints at 0°and 90°,the shear crack extends horizontally until it penetrates the specimen.For specimens with joints at 30°,45°,and 60°,the direction of shear crack propagation aligns with the joint angle.