FLAC3D流固耦合渗流模型探讨

FLAC3D有限元软件内置4种渗流模型，直接决定计算结果正确与否。渗流场在三维空间中分布复杂，难以根据计算公式定量选用何种模型，不同文献渗流模型选择标准也不相同。为了找到简单、快速、合理的选择方法，有必要对4种渗流模型进行受力分析。以一100 m×100 m×10 m各项同性弹性立方体为例，基于4种渗流模型设计4种工况。通过对比和分析各工况下总应力和孔隙水压分布情况，主要结论如下： 1）模型A、模型C外荷载均由土颗粒骨架承担，其余2种模型流体也参与受力； 2）流体分担外荷载的比例与刚度系数和时间有关； 3）FLAC3D流固耦合过程正是通过调整刚度比、打开和关闭力学-流体进程来实现的。目前我国流固耦合计算基本基于FLAC3D有限元软件，文中结论适用于基础、隧道、基坑等工程，可供相关从业人士借鉴参考。

Discussion on Seepage Model Based on FLAC3D Solid fluid Coupling

There are 4 seepage models in the FLAC3D finite element software; it is decided by selecting proper seepage models whether the result of numerical calculation is right or not. The seepage field distribution in three dimensional space is complicate; as a result, it is difficult to decide a quantitative yardstick. There are different selection methods in different references. It is necessary to make stress analysis on the 4 seepage models, so as to choose a simple, rapid and rational model selection method. Four construction cases based on the 4 seepage models are designed, with a 100 m×100 m×10 m isotropic elastic cube as an example. The total stresses and seepage field distributions of the 4 construction cases are compared. The conclusions drawn are as follows: 1) For model A and model C, the soil skeleton carries all loads; for other 2 models， the fluid carries partial load too. 2) The load sharing ratio of fluid is based on the stiffness ratio and time. The solid fluid coupling process in FLAC3D is realized by adjusting the stiffness ratio and switching mechanics fluid process. So far, the calculation of solid fluid coupling is almost based on FLAC3D in China. The conclusions can be applied to foundation engineering and underground engineering, and the paper can provide reference for similar projects.