泥岩核废料处置库温度-渗流-应力耦合参数敏感性分析

Parameter sensitivity analysis for thermo-hydro-mechanical coupling model of clay tunnel for radioactive waste disposal

针对比利时HADES地下实验室PRACLAY现场加热试验,应用温度-渗流-应力耦合弹塑性模型,模拟现场加热过程中泥岩核废料处置库的水力学响应特征。采用单因素分析法,就泥岩热、水、力学参数对核废料处置库围岩孔压、温度、有效应力的影响进行了三维有限元分析。并基于参数敏感性分析结果,就温度、渗流、应力三场两两耦合作用对处置库围岩水力学响应的影响程度进行了系统分析。研究结果表明:泥岩热、水、力学参数中,渗透系数、弹性模量以及导热系数对加温所导致的超孔压的值影响较大;凝聚力、内摩擦角以及热膨胀系数对孔压的影响较小,但会显著影响围岩的有效应力;导热系数对围岩温度场的分布有决定性影响,温度传递的差异会显著影响围岩的孔压和有效应力;不同的热、水、力学参数对孔压、温度以及有效应力的影响机制是不同的,温度、渗流、应力三场两两耦合作用对围岩水力学响应的影响程度也存在显著的差异性。温度场对应力场、温度场对渗流场的耦合效应十分显著,加热后,围岩超孔压的产生以及热膨胀导致的有效应力变化会显著影响处置库的稳定。该研究结果在一定程度上可以为核废料处置库泥岩的热、水、力学参数的确定及耦合机制分析提供科学依据。

A thermo-hydro-mechanical coupled model was used to simulate hydraulic reaction of the PRACLAY in-situ heating experiment which was conducted in Belgium underground laboratory HADES. The 3D finite element simulation was performed for the sensitivity of parameters to the pore water pressure, effective stress and temperature of surrounding rock under thermo-hydro-mechanical coupled conditions by using a single factor analysis method. The effects of two coupling factors among temperature, seepage and stress were comprehensively investigated upon hydraulic reaction of rock around the repository. It is shown that the permeability, elastic module and thermal conductivity are the uppermost ingredients influencing the pore water pressure. The cohesion, friction angle and thermal expansion efficient have a negligible effect on the pore water pressure, but have a remarkable effect on the effective stress. The distribution of temperature field of surrounding rock is only affected by the thermal conductivity. The influence mechanism of various parameters on pore pressure, temperature, and effective stress is different. There exists a difference in the effects of two coupling factors among temperature, seepage and stress upon hydraulic reaction of surrounding rock. The strongest coupling is found from thermal to hydraulic and mechanical behaviour. The excessive pore pressure induced by heating greatly affects the stability of surrounding rock, so does the variation of effective stress caused by thermal expansion. The results of this study have a certain value for the determination of parameters and analysis of coupling mechanisms of clay tunnel for radioactive waste disposal.