平面应变状态下岩石剪切带网络数值模拟研究

Simulation of nultiple shear bands in strain softening rock in plane strain

研究了围压、端面约束、试件高度及界面特性对剪切带网络形成的影响。首先对影响剪切带网络形成的因素(包括试件高度、围压及温度、试件端部轴向应变大小的计算方法的差异)进行了分析。之后采用FLAC 3D对平面剪切带网络进行了数值模拟,其中摩擦角及内聚力为应变软化。探讨了倾向于出现剪切带网络的若干条件。若端面缚束较强且存在一定的侧压力,试件中部出现多重剪切带。若端面缚束较弱,试件端部易于形成剪切带网络,且随试件高度的增加剪切带条数增加。界面法向和切向刚度越大,剪切带穿越断层并按其固有方向延伸能力越强,剪切带网络格局越明显。获得的数值结果可在实验中找到佐证,并且可以用来解释地震中的一些剪切应变局部化现象。

The influences of confining pressure, end constraint, height of specimen and interface on networks of shear bands are investigated numerically. Firstly, some factors including height of specimen, confining pressure, temperature, axial strain and different numerical methods were discussed. Secondly, the FLAC 3D was used to simulate planar multiple shear bands and friction angle and cohesion force were dependent on plastic strain. The conditions, under which the multiple shear bands tend to form, were discussed. As end constraint is strong and confining pressure exists, the multiple shear bands appear in the center of specimen. For weak end constraint, the multiple shear bands form in the end of the rock specimen and numbers of shear bands increases with height of specimen. For large normal and tangential rigidity, shear bands can penetrate old fault and propagate along their inherent directions and the form of networks of shear bands is very apparent. The results obtained agree with many experimental tests and can be used to explain some phenomena of shear strain localization in seism.