Evaluation of seismic bearing capacity on layered geological strata by the upper-bound numerical method

Abstract

This study introduces the Energy Method Upper-bound (abbreviated as EMU), originally proposed by Donald and Chen (1997), for calculating bearing capacities with a focus on earthquake loadings affecting layered geological strata. The theoretical components of this study consist of (1) an extension of Prandtl's solution for bearing capacity analysis to inclined surface loads, (2) a mathematical demonstration of the theoretical congruence between EMU and the Prandtl-Reissner solution, and (3) a validation of the numerical outcomes through four illustrative bearing capacity examples with known closed-form solutions. This innovative approach eliminates the semi-empirical coefficients typically required in conventional bearing capacity evaluations, thus enhancing its relevance to seismic analysis for stratified geological formation that can hardly be evaluated with empirical coefficients accurately. The study also discusses various technical aspects such as seismic load determination, the use of undrained shear strength, and specifications for allowable safety factors under seismic conditions. With these methodologies, the paper assesses the seismic bearing capacities of two different buildings, with different scales and footing types. Additionally, a computer program, BEARING-IWHR, featuring an Excel interface and open-source coding, is available online. This method provides a theoretically sound and practically feasible framework for addressing seismic bearing capacity on stratified foundations.