不连续面在双重介质热-水-力三维耦合分析中的有限元数值实现

Numerical implementation of discontinuities in dual media 3D model for thermo-hydro-mechanical coupling

在建立双重介质热-水-力耦合微分控制方程的基础上,提出了裂隙岩体热-水-力耦合的三维力学模型,对不同介质分别建立以节点位移、水压力和温度为求解量的三维有限元格式,开发了双重介质热-水-力耦合分析的的三维有限元计算程序,在有限元数值分析中不连续面应力计算采用等厚度空间8节点节理单元进行离散,而不连续面渗流和热能计算时采用平面4节点等参单元进行离散,这样保证了不同介质之间的水量、热量交换和两类模型接触处节点水头、温度和位移相等。通过高温岩体地热开发算例,揭示了在热-水-力耦合作用下不连续面处于低应力区,其张开度随运行时间的延长呈非线性增加,非稳定渗流阶段不连续面显著地控制着渗流场的整体分布,它的水头远高于拟连续岩体介质的水头,而进入稳定渗流阶段不连续面的控渗作用不明显,由于高温岩体地热开发系统中存在大规模的热量补给,不连续面对岩体温度场分布的影响并不显著。

Based on the differential control equations of the coupled thermo-hydro-mechanical processes of dual media, a three dimensional coupled model of dual media to research coupled thermo-hydro-mechanical（THM） processes of fractured rock masses, is proposed. In coupled model, the values of nodal displacement, water pressure and temperature in different media were solved. A three dimensional FEM code. for analysis of coupled thermo-hydro-mechanical processes of dual media is developed tentatively, in FEM program, 3D jointed elements with 8 nodes were used to simulate the crack elements during the stress analysis of discontinuities; and 2D isoparametric elements with 4 nodes were used to simulate discontinuities during seepage and heat energy analysis of discontinuities. So the different media can exchange water and heat flux, water head, temperature and displacement of nodes which are in the interface between two models were equal. Through the numerical computation for heat extraction in HDR; it is shown： that in the thermo-hydro-mechanical coupling process, discontinuous is in low stress state; the crack width increases nonlinearly with the heat extraction; in transient fluid flow stage, the water head in discontinuities was higher than equivalently continuous rock medinm; in steady fluid flow phase, the dominant effect of discontinuities on fluid flow would unconspicuous. Because of massive heat replenishment, the compact of discontinuities on temperature distribution was indistinctive.