核废料地质贮存介质黏土岩的三维各向异性热-水-力耦合数值模拟

NUMERICAL SIMULATION OF 3D COUPLED THERMO-HYDRO-MECHANICAL ANISOTROPY OF ARGILLITE ROCK FOR RADIOACTIVE WASTE DISPOSAL

为了解黏土岩在放射性废料长期贮存中的热-水-力耦合过程,结合MontTerri核废料贮存地下岩石试验工程中黏土岩各种物理量的各向异性特点,应用多孔介质力学耦合理论研究了该黏土岩在加热和冷却全过程中由于热荷载引起的耦合效应场。研究过程考虑温度升高引起的孔隙水黏滞性改变对渗透系数的影响。研究结果表明,岩体力学参数、水力学参数和热传导参数的各向异性特性是影响岩体的温度场、孔隙压力场和应力场分布的最主要因素。各向异性耦合模型与各向同性耦合模型的数值模拟对比研究结果表明:各向异性模型数值结果能更加客观地反映该地下岩石试验工程中黏土岩在受热状态下的热-水-力耦合效应;同时,也表明岩体在加热过程中一直处于受压状态,而在冷却过程中局部会出现拉应力,从而有可能导致拉裂缝的产生。

For better understanding of thermo-hydro-mechanical coupling processes of argillite rock in Mont Terri project site during the long-time radioactive waste disposal,coupled fields of temperature,pore pressure and stress are studied during the heating and cooling phases with the theory of porous media mechanics.The anisotropy of thermo-hydro-mechanical behaviour is considered simultaneously during the calculation.The influence of the variation of water viscosity due to temperature variation on permeability of pore water is also considered during the simulation.The whole process of excavation,heating phase and cooling phase have been simulated in the calculation;and the calculated results are analyzed.It indicates that the anisotropy of thermo-hydro-mechanical behaviour of the argillite rock is the main factor affecting temperature distribution,pore pressure and stress fields.By comparing the simulated results of coupled isotropic model and anisotropy model,it is shown that the numerical results of coupled anisotropy model can objectively describe the coupled thermo-hydro-mechanical effect of the argillite rock located in the underground rock laboratory with thermal load.The simulation results also indicates that the argillite rock undertakes the compressive stress during the heating phase,while it undertakes tensile stress locally during the cooling phase;and these tensile stress maybe induce the generation of cracks in the rocks.