高孔隙岩石变形的离散单元模型

A discrete element model of porous rock deformation

实验和野外观测表明颗粒破碎显著影响高孔隙岩石的变形特征.为建立高孔隙岩石变形的数值模型,我们以弹性理论为基础并根据问题的特征进行合理简化,给出了一种颗粒破碎机制,并根据此颗粒破碎条件改进传统的离散单元模型.利用改进的离散单元模型,研究了不同压力条件下高孔隙岩石变形的宏观和微观特征.数值模拟结果表明考虑颗粒破碎的模型能重现高孔隙岩石在不同围压下变形的应力-应变关系、声发射特征、应变局部化和剪切增强压缩等特征.我们还发现,与野外观测结果一致,在高孔隙岩石脆性阶段剪切带内部及附近伴有显著的颗粒破碎.

Laboratory and field observations show that grain crush can rocks. To construct a numerical model for porous rocks, we obtain a prominently affect deformation of porous simplified grain crush criterion based on the theory of elasticity and reasonable assumption. This criterion is introduced into the traditional Distinct Element Model （DEM）. The modified model is used to study the macro and micro behaviours of high porosity rock under different confining pressures. It is proved that the model adopting grain crush mechanism can reproduce the character of stress-strian relation, AE rate, strain localization and shear enhanced compaction which are in good agreement with laboratory and field observations. We have also found that similar to field results, in the numerical model many crushed grains are located inside and near the developed shear band, which is not mentioned in previous models.