Some problems in numerical analyses of basal upheaval stability of foundation pits

Numerical analysis of basal upheaval stability of foundation pits is a very important method in researches on deep excavation engineering, which is in the initial development stage and is of important issues remained to be understood and solved. Based on analysis of the results of the corresponding researches, combining the experience gained from the researches in three-dimensional parametric analysis of excavation in soft soils, the problems such as spatial effects, failure patterns, selection of soil constitutive models and their parameters are analyzed. Both the three-dimensional analyses and the bilateral plain analyses of basal upheaval stability are emphased. The differences of failure patterns of basal upheaval from numerical analyses and those from the traditional analytical methods in failure pattern recognition are revealed. The great importance should be attached to the loading and/or unloading criteria and yield and failure criteria in selection of soil constitutive models and their parameters. The concept of feasible region for parameters in parametric analysis is firstly put forward.