Probabilistic Analysis of Basal Heave in Deep Excavation

Abstract

The deterministic model using the factor of safety against basal heave (FS) defined as the ratio of soil resistance over mobilized force is usually used to evaluate the failure of basal heave in excavation. However, such deterministic method cannot deal with model and parameter uncertainty. In this study, one excavation case, in which the basal heave failure has occurred, is employed to study its probability of failure. The uncertainty of undrained shear strength of soil is considered in the analysis based on laboratory tests presented in past studies. The Monte Carlo simulation is then used to perform the probabilistic analysis of basal heave. Results show that the probability of failure for basal heave computed based on the original design and UU test results can be as large as 40% when FS equals to 1.0 and COV of undrained shear strength is equal to 0.2. The probabilistic analysis of basal heave can provide valuable information to advance the excavation design.