剪切带图案的复杂性及应力-应变曲线的离散性

摘要/Abstract

摘要： 在平面应变压缩条件下，通过在岩样左边界靠近下端面的位置及右边界的不同位置预制材料缺陷，采用拉格朗日元法研究了材料缺陷位置不同时的剪切带图案启动、演变及试样的宏观力学行为。在数值计算中，采用了莫尔-库仑与拉破坏复合的破坏准则，峰后岩石的本构关系为线性应变软化。当试样左、右边界上的缺陷距离较远时，剪切带仅出现1条，以通过两缺陷形式贯通试样两边界；当两缺陷距离较近时，启动于缺陷附近的剪切带按各自其固有方向发展，剪切带图案十分复杂。当右缺陷距离试样上端面较近时，由于上端面的约束，仅位于缺陷下方的剪切带能得到充分的发展。若剪切带数量较少且贯通试样两边界时，试样发生脆性剪切破坏，应力-变形曲线软化段比较陡峭；反之，发生韧性剪切破坏，软化段比较平缓。当剪切带的前端迎面遇到试样上、下端面附近的上、下三角形区域时，由于端面的约束，剪切带的方向将改变。当剪切带的前端与试样的纵向对称线距离较近时，剪切带发生折射现象；当距离较远时，剪切带将发生反射现象。

关键词: 岩石力学, 剪切带, 材料缺陷, 应力-应变曲线, 端面约束, 韧性剪切破坏, 脆性剪切破坏

Abstract: Effects of positions of material imperfection at right edge of rock specimen under plane strain compression on initiation and evolution of shear bands as well as stress-strain curves of rock specimen were modeled numerically by FLAC. Two material imperfections were introduced in the form of null element at left and right edges of specimen, respectively. The material imperfection at left edge was fixed; however, the positions of material imperfection at right edge were different for different schemes. The adopted failure criterion was a composite Mohr-Coulomb criterion with tension cut-off and post-peak constitutive relation of rock was linear strain-softening. Only one shear band bisecting specimen through two imperfections is formed and only full development of shear band below right material imperfection is permitted due to end restraint at top of specimen when right imperfection is close to the top. When right imperfection is not close to the top, shear bands are initiated in the vicinity of material imperfections and propagate along their inherent directions so that patterns of shear bands are very complex. Stress-strain curve beyond the peak strength exhibits steeper behavior when the number of shear bands intersecting specimen is lower. Otherwise, strain-softening branch of stress-strain curve undergoes ductile behavior. In the process of shear band propagation, when the tip of shear band head-on approaches two triangular regions affected by strong restraint at top or base of specimen, direction of shear band has to be changed. If the tip is very closer to the symmetrical line in vertical direction of specimen, direction of shear band will be slightly changed (the phenomenon is called shear band refraction). However, if the tip is not very closer to the symmetrical line, the direction will be changed greatly (the phenomenon is called shear band reflection).

Key words: rock mechanics, shear band, material imperfection, stress-strain curve, end restraint, ductile shear failure, brittle shear failure

中图分类号:

TU 451

王学滨. 剪切带图案的复杂性及应力-应变曲线的离散性[J]. , 2005, 26(S1): 25-30.

WANG Xue-bin. Complexity of shear band patterns and discreteness of stress-strain curves [J]. , 2005, 26(S1): 25-30.

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