FLAC3D流固耦合渗流模型探讨

Discussion on Seepage Model Based on FLAC3D Solid-fluid Coupling

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。

There are 4 seepage models in the FLAC3 D 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 FLAC3 D is realized by adjusting the stiffness ratio and switching mechanicsfluid process. So far,the calculation of solid-fluid coupling is almost based on FLAC3 D in China. The conclusions can be applied to foundation engineering and underground engineering,and the paper can provide reference for similar projects.