塑性扩容梯度对孔隙介质岩体中T-H-M耦合作用的二维有限元分析

由双重孔隙-裂隙介质热-水-应力耦合模型退化为单一孔隙介质模型,将其与岩体扩容梯度引入笔者所研制的二维有限元程序中,使用Mohr-Coulomb准则,计入塑性扩容对岩体孔隙率及渗透系数的影响,针对一个假设的实验室尺度且位于饱和孔隙介质岩体中的高放废物地质处置库模型,拟定不同扩容梯度值的5种工况,进行4年处置时段的数值模拟,考察了岩体中的温度、正应力、塑性区、孔隙率及渗透系数、孔隙水压力和地下水流速的变化、分布情况。结果主要显示,相比于不考虑扩容梯度的工况,考虑扩容梯度工况的正应力、孔隙率及渗透系数、孔隙水压力和地下水流速等的分布与塑性区的分布有明显的对应关系,呈现了某种"剪切带效应";正应力量值、塑性区面积、孔隙率及渗透系数、孔隙水压力、地下水流速等均随所取扩容梯度值的变大而增加。

2D finite element analyses of effects of plastic dilatancy gradient on T-H-M coupling in porous rock mass

The coupled thermo-hydro-mechanical (T-H-M) model for dual- pore-fracture media was degenerated into a model for single pore media; then this model and the gradient of rock dilatancy was introduced into the FEM code developed by the first author; also the Mohr-Coulomb yield criterion was used and the effects of dilatancy of plastic rock on porosity and permeability of rock mass were considered. Aiming at a model of hypothetical nuclear waste repository in a saturated porous rock mass with a laboratory scale, five computation cases with different values of rock dilatancy gradient were designed; then the corresponding numerical simulations for a disposal period of 4 years were carried out; and the states of temperatures, normal stresses, plastic zones, porosities and permeabilities, pore pressures as well as flow velocities in the rock mass were investigated. The results show that：compared with the case without considering dilatancy gradient, the distributions of normal stresses, porosities and permeabilities, pore pressures and flow velocities correspond to obviously the distributions of plastic zones, so some “shearing effects” are presented; all of the values of normal stress, areas of plastic zones, porosities and permeabilities, pore pressures and flow velocities increase with the raise of given dilatancy gradient.