Deterministic and reliability analysis of basal heave stability for excavation in spatial variable soils

Nonlinear finite element analyses for deep excavations in soft clay with different geometrical properties of the excavation, wall and soil properties were carried out to assess the basal heave factor of safety. The study indicated that the increase in the basal heave factor of safety with increasing wall penetration depth is more significant for diaphragm walls compared with sheetpile walls. The analyses also highlight that the depth to the hard stratum from the tip of the wall is a key component of the resistance of the excavation system to basal heave failure. A comparative study of the basal heave factor of safety predicted by the finite element analysis with some commonly used limit equilibrium methods was also carried out. Subsequently, reliability analyses that considered the spatial variability of the soft clay were performed and some useful conclusions regarding the effects of spatial averaging as well as the coefficient of variation of the soil properties are presented.