Analysis of excavation in an elasto-plastic soil involving drawdown of the water table

Abstract

A numerical method is presented which may be used for the solution of problems involving excavation below the water table. When such excavations are carried out, movement of the surrounding soil is caused by two main factors; firstly there is movement due to stress release and secondly, if flow can occur into the excavation, there is settlement caused by the lowering of the water table. In this paper, a fully coupled solution is presented to the groundwater flow -soil deformation problem. Non-linearity of the soil behaviour is introduced through the use of the well known Modified Cam Clay model. The problems of correctly determining the equivalent tractions to be removed from the finite element mesh when simulating excavation, and of determining the position of the free surface of the groundwater are also discussed. An example is given for a simple problem in order to illustrate the theory. Soil displacements, stress fields, fall of the free surface and pore pressure fields are some of the results which are presented.