Influence of Spatially Varying Soil on Basal Heave Analysis of Braced Excavation

The basal heave of excavation is generally evaluated with a factor of safety. In reality, the implementation of the probability analysis, in which the uncertainties of models and parameters can be adequately considered, is beneficial to the design of geotechnical engineering. Of various sources of uncertainties, the spatial variation of stratigraphy is a quite new research topic and its effect on the engineering behavior is still required further studied. This study aimed at investigating the effect of spatial variation on analysis of excavation basal heave in soft clay. The basal heave analysis proposed by the Taiwan building code, as well as the random field theory, is adopted to be capable of simultaneously considering the uncertainties and spatial variation of geomaterial in such analysis using Monte Carlo simulation. An actual excavation case history, in which the basal heave occurred, is used to conduct the intended analysis. Comparing with the conventional deterministic analysis method, the analysis results revealed that the probability of failure against basal heave would be reduced when the spatial variation is considered in the analysis.