Deterministic and probabilistic basal heave stability analysis of circular shafts against hydraulic uplift

Abstract

Circular shafts are commonly required for urban development. Their construction often encounters underground water, which can make shafts more prone to hydraulic heave and to soil uplifts which may cause serious accidents. Therefore, the basal heave stability analysis of shafts subjected to a hydraulic uplift is essential to ensure their safety. In this study, deterministic and probabilistic analyses of supported circular shafts in clayey soils subjected to hydraulic uplifts are presented. The effects of the permeability anisotropy coefficient (rk), the soil-wall interface strength coefficient (ri) and the soil tension cut-off coefficient (rt) are discussed. The basal heave safety factor is evaluated by a Finite Element Limit Analysis (FELA). A Stochastic Finite Element Limit Analysis (SFELA) is introduced to perform the probabilistic analyses by coupling the FELA, an adaptive Polynomial Chaos Kriging (PCK), the Monte-Carlo Simulations (MCS), the First Order Reliability Method (FORM) and the Global Sensitivity Analysis (GSA). It is then carried out to get valuable probabilistic results. Several academic cases are considered: (1) effects of rk on the flow vectors, seepage pressures and water head distributions; (2) effects of rk, ri and rt on the shaft stability considering by safety factor and failure probability; (3) importance rank of rk, ri, soil cohesion and friction angle. The results indicate that the permeability anisotropy coefficient, the soil-wall interface strength and the tension cut-off have a remarkable influence on the circular shaft stability when a hydraulic uplift is considered.