Influence of non-stationarity in friction angle on the performance of the braced excavation system

This study aims to quantitatively evaluate the deformational response of braced excavations in the presence of existing infrastructure while considering the spatial variability of the internal friction angle of soil. The spatial variability is characterized by a non-stationary random field of linearly increasing mean and constant coefficient of variation with depth. Probabilistic analysis with stationary random fields is first performed to provide a reference for the subsequent analysis with non-stationary random fields. The influence of friction angle gradient and vertical scale of fluctuation on excavation-induced deformation responses, such as maximum lateral wall deflection and maximum ground surface settlement, is studied. The findings indicate that neglecting the depth-dependent variation of the friction angle results in an overestimation of lateral earth pressure, which in turn leads to higher values of maximum lateral wall deflection and maximum ground surface settlement. It is also observed that the friction angle gradient significantly affects the location of maximum lateral wall deflection in braced excavation. Additionally, the failure probability of individual components and the overall failure of the braced excavation system are evaluated, considering multiple ultimate and serviceability criteria. A new parameter, building wall torsional tilt, which indicates the degree of differential settlement, is adopted as a serviceability criterion for buildings.