渗透系数对渗流速度影响的热-水-应力耦合二维有限元分析

Coupled thermo-hydro-mechanical analyses of influence of permeability coefficient on flow velocity with 2D finite element method

使用建立的饱和-非饱和介质中热-水-应力耦合弹塑性模型,取一组真实的缓冲材料、岩体及贮存容器(用加热器代替)的物理力学指标作为基本计算条件,以一个假想的核废料处置库为模拟对象,就高、中、低3种渗透系数进行了二维有限元数值分析,考察了近场的渗流速度大小及方向的变化,认识到:在其他计算参数相同的条件下,缓冲材料的渗透系数越高,近场的渗流速度越大,缓冲层达到饱和状态也越快;当缓冲层达到饱和状态后,如果玻璃固化体继续放热,有可能使得近场的温度梯度的作用强于水力梯度的作用,导致渗流速度方向发生逆转,即水分由内向外迁移;依渗透系数不同,其渗流速度的大小、方向有显著差异,这也势必引起放射性核素随地下水流动扩散的复杂多变。

Using the coupled thermo-hydro-mechanical model for saturated-unsaturated porous media developed by the author and taking one set of real physical and mechanical parameters of buffer material, rockmass and canister （replaced by heater） as the basic computation condition, this paper conducts 2D FEM analyses for a hypothetical nuclear waste repository, in which high, middle and low permeability values were applied. Though investigating the change of magnitudes and directions of the flow velocities in the near field, it is realized that： under the condition that the other computation parameters are the same, the higher the permeability of the buffer, the faster the flow, and the time for the buffer to enter a saturated state is also shorter; after the buffer reaches the saturation state if the vitrified waste releases heat continuously, the action of the temperature gradient in the near field may exceed the action of the hydraulic gradient, so that the direction of the flow velocity reverses and the water transports from the inside to the outside; the flow velocity fields have an obvious difference according to different permeability values so that the diffusion of radioactive nuclide with underground water flow is also complex and changeable.