缺陷岩样的变形局部化及剪切面的反射与折射

Strain Localization of Rock Specimens with Imperfections and Refraction and Reflection of Shear Bands

平面应变岩样在单方向施加载荷条件下,采用拉格朗日元法(FLAC)模拟了端面约束对具有初始随机材料缺陷的岩样破坏过程及应力-应变曲线的影响.对于粗糙端面试样,可在试样中部观测到剪切带;靠近试样两端面的弹性区域的形状类似三角形,其高度随着轴向应变的增加而降低,直到达到常数.对于光滑端面情形,未观测到剪切带的停滞及折射现象,而反射现象较常见.对于粗糙端面试样,剪切带不能贯穿试样的两端面;很少观测到反射现象;可见到剪切带的停滞现象;剪切带的折射现象较常见;通常,一条较长的剪切带可以贯通试样;剪切带发生折射之后,其倾角有所降低.粗糙端面时的应力峰值比光滑端面时高.端面约束不同时的峰后刚度及应力峰值所对应的轴向应变没有明确的规律.不同端面条件下,试样中部剪切带花样既有一定的类似性(由于微弱的端面约束与相同的初始随机材料缺陷分布),又有不同的一面(端面约束的不同及两端面附近的剪切带传播至试样中部).

For heterogeneous rock with initial random material imperfections in plane strain compression, the effects of end-restraint on the failure process and the stress-strain curve are numerically modeled, using FLAC. In the case of rough ends, shear bands （SBs） are observed in the middle of specimens. The shape of elastic zones closer to the ends of specimens is like a triangle whose height decreases with increasing axial strain until it reaches a constant value. In the case of smooth ends, SB refraction and decease cannot be observed, while SB reflection is common. In the case of rough ends, SBs cannot intersect the any end of a specimen. SB reflec- tion is seldom observed, but SB decease can he observed close to the ends of specimens. SB re- fraction is also common; usually, a SB bisecting the specimen can be observed. SB inclination decreases once SB refraction occurs. The peak stress at smooth ends is lower than that at rough ends. The effect of end-restraint on the post-peak stiffness and axial strain corresponding to the peak stress is unclear. SB patterns at different end-restraints have a certain similarity in the middle of specimens due to weak end-restraint and a similar distribution of initial random im- perfections. At various end-restraints, SB patterns near the ends of specimens are variable,leading to different SB patterns in the middle of specimens since SBs propagate from the ends towards the middle.