应力腐蚀和压力溶解作用下双重孔隙岩体中 THMM耦合过程的有限元分析

在使用Yasuhara等建立的裂隙开度的应力腐蚀和压力溶解模型的基础上，将溶质浓度场引入笔者已开发的双重孔隙-裂隙介质热-水-应力耦合的二维有限元分析程序中，针对一个假设的位于非饱和岩体中且有核素泄漏的高放废物地质处置库，拟定2种计算工况：（1）裂隙开度随应力腐蚀和压力溶解而变化（基岩的孔隙率亦是应力的函数）；（2）裂隙开度和基岩的孔隙率均为常数，进行热-水-应力-迁移耦合的数值模拟，考察了岩体中的温度、裂隙开度的闭合速率、闭合量、孔（裂）隙水压力、地下水流速、核素浓度和应力的变化、分布等情况。结果主要显示：应力腐蚀引起的闭合速率要高于压力溶解引起的闭合速率6个数量级，且两种因素产生的闭合速率随时间先增加后减小，并趋于稳定；当考虑应力腐蚀和压力溶解时，近场的负裂隙水压力上升很高；工况1中裂隙开度和孔隙率减小，使得相应的渗透系数降低，故该工况的裂隙和孔隙中核素浓度较工况2为高；由于不计入负的孔（裂）隙水压力对应力平衡的影响，2种工况的岩体中的应力量值及分布基本相同。

FE analysis of THMM coupling processes in dual-porosity rock mass under stress corrosion and pressure solution

On the basis of using the models of stress corrosion and pressure solution established by Yasuhara et al,the solute concentration field is introduced into the 2D FEM code of thermo-hydro-mechanical coupling analysis for dual-porosity medium developed by the authors.Aiming at a hypothetical nuclear waste repository in unsaturated rock mass from which there is a nuclide leak,two computation conditions are designed:(1) the fracture apertures are changed with the stress corrosion and pressure solution(the porosity of intact rock is also a function of stress);(2)the fracture apertures and the porosity of intact rock are constants,then the corresponding two-dimensional numerical simulation for the coupled thermo-hydro-mechano-migratory processes is carried out;and the states of temperatures,rates and magnitudes of aperture closure,pore and fracture pressures,flow velocities,nuclide concentrations and stresses in the rock mass are investigated.The results show that the aperture closure rates caused by stress corrosion are almost six orders higher than those caused by pressure solution;and the two kinds of closure rates climb up and then decline,furthermore tend towards stability;when the effects of stress corrosion and pressure solution are considered,the negative fracture pressures in near field rise very high;the fracture aperture and porosity decrease in the case 1,so the relative permeability coefficients reduce;therefore the nuclide concentrations in pore and fracture in this case are higher than those in case 2 because the effects of negative pore and fracture pressures on the stress balancing are not reckoned in;the magnitudes and distributions of stresses within the rock mass in two calculation cases are almost the same.