Strength reduction method for safety coefficient of heave-resistant stability of asymmetrically-loaded excavations in soft soil areas

A two-dimensional finite element model incorporating the strength reduction method is established to study the base heave problem encountered in asymmetrically-loaded excavations in soft soils. The parametric studies are conducted to investigate the influences of distribution range, distance from the bracing structures and amplitude of the asymmetric loading on the base-heave resistance factor. Meanwhile, comparisons are made among the above numerical results, the limit equilibrium method and the limit analysis method. The analysis results show that the heave-resistance factor decreases when the distribution range of the asymmetric loading increases or the distance between the asymmetric loading and the bracing structures decreases. The base-heave resistance factors of excavations with different depth/width ratios all show a linear decrease with the increasing amplitude of asymmetric loading. Compared to the strength reduction method, both the Terzaghi limit equilibrium method and the limit analysis method overestimate the base-heave resistance factor of an asymmetrically-loaded excavation, while both the Bjerrum & Eide limit equilibrium method and the code method (based on Prandtl mode) are conservative since they underestimate the factor.