Probabilistic basal heave stability analyses of supported circular shafts in non-homogeneous clayey soils

Abstract

Circular shafts are commonly used to construct accesses to facilitate tunnel boring machine works and can be used as ventilation systems, subway stations or emergency exits. This study presents a probabilistic analysis of supported circular shafts in undrained and non-homogeneous clayey soils to reflect the uncertainty influences of the soil undrained shear strength at the ground surface, non-homogeneity coefficient, unit weight and soil-wall adhesion factor. The basal heave safety factor is evaluated by an axisymmetric lower bound Finite Element Limit Analysis and a probabilistic analysis is discussed using the adaptive Polynomial Chaos Kriging technique-based Monte-Carlo Simulation and a Global Sensitivity Analysis (GSA). After deterministic and probabilistic comparisons, academic cases are performed to get some insights for the following problems: (1) importance of the uncertainty’s consideration; (2) effect of the soil-wall interface; (3) influence of non-homogeneous soils on the circular shaft’s stability. Besides, some sensitivity analyses are conducted to discuss the input random variables importance. Obtained results show that the coefficient of variation, soil-wall adhesion factor and soil non-homogeneity coefficients have a remarkable influence on the circular shaft stability.