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假定骨架、固体颗粒和水均是可压缩的,在此基础上采用两相不混溶流体的理论推导了水的连续方程,通过引入气压恒定这一假定进一步简化为水的非饱和渗流连续方程。基于广义Biot理论给出了固体骨架积分形式的平衡方程,结合非饱和渗流连续方程采用加权残值法推导了流固耦合方程组的有限元列式。通过干燥介质吸水的数值模拟来考察非饱和流固耦合模型的预测能力,数值模拟的结果表明耦合模型可以准确地反映吸水过程的规律。将耦合模型应用于水下大断面隧洞开挖的瞬态分析,可以模拟出开挖引起的EDZ区域孔隙水压力急剧升高、有效应力减小、渗透系数动态变化以及排水对洞室稳定性的影响,计算的结果与国外大型原位实验的一般性观测结论相吻合。
Assuming that the skeleton, solid particles and water are both compressible, the continuous equation of water is deduced based on the theory of two-phase immiscible fluids. By introducing the assumption of constant air pressure, the continuous equation of unsaturated seepage for water is further simplified . Based on the generalized Biot theory, the equilibrium equation of the integral form of the solid skeleton is given. The finite element formulation of the fluid-solid coupling equations is derived by using the weighted residual method in combination with the unsaturated seepage continuity equation. Through the numerical simulation of water absorption in dry medium, the predictability of unsaturated fluid-solid coupling model is investigated. The numerical simulation results show that the coupled model can accurately reflect the law of water absorption. Applying the coupled model to the transient analysis of excavation of large cross-section tunnels can simulate the rapid increase of pore water pressure, the decrease of effective stress, the dynamic change of permeability coefficient and the stability of cavity in EDZ caused by excavation The results of the calculation are consistent with the general observations of large-scale in situ experiments abroad.