孔隙气压对核废物地质处置热-流-固耦合影响的有限元分析

Finite element analyses of influence of pore gas pressure on coupled thermo-fluid-mechanical processes in geological disposal of nuclear waste

为考察孔隙气体压力对高放废物地质处置中的热-流-固耦合过程的影响,借用Leiws等建立的可变形孔隙介质中非等温空气流和水流模型,在其水连续性方程中加入了温度梯度引起的水分扩散项,研制出相应的热-水-气-应力耦合弹塑性二维有限元程序。针对一个假定的高放废物地质处置库模型,在相同的初始温度、孔隙水压力和岩体应力条件下,取3种缓冲层中的初始孔隙气体压力,通过数值模拟考察了处置库近场的主应力、饱和度、气和水的流速、温度和孔隙压力的分布与变化。结果显示,当缓冲层中的初始孔隙气压力较高时,其对围岩中应力影响较大。

In order to investigate the influence of pore gas pressure on the coupled thermo-fluid-mechanical processes in geological disposal of high-level radioactive nuclear waste, a 2D elastoplastic FEM code was developed by using the model of non-isothermal air flow and water flow in a deforming porous medium suggested by R. Leiws et al, in which an item of thermal water diffusion was added by the author. Against an assumed model of geological disposal of nuclear waste, the numerical simulations in which three kinds of original pore gas pressure in the buffer were applied, were carried out under the conditions of the same initial temperature, pore water pressure and in-situ stress. The distributions and changes of the principal stresses, saturations, fluid flow velocities, pore pressures and temperatures in near field of the disposal model were analyzed. The results show that the higher original pore gas pressure in the buffer gives a bigger effect on the stresses in rock.