Pore-Pressure Dissipation During Excavation

A finite element analysis procedure is presented that allows analysis of the actual degree of pore-pressure dissipation that occurs during and after excavation. Allowances are made for nonlinear soil behavior, variations in rate of the excavation process, and the presence of impervious support wall sysstems. The validity of the program is checked by comparing predicted results with closed-form one-dimensional solutions, and data obtained in partially drained plane strain tests on a clayey soil. The computed response is found to agree exactly with theoretical results and to closely approximate that observed in the soil tests. In order to investigate dissipation of excess pore pressures for excavations, the results of a series of analyses of one-dimensional and two-dimensional problems are presented. It is found that significant pore-pressure dissipation is likely to occur during excavation except where the soil deposit is of low permeability.