3D stability analysis of unsupported rectangular excavation under pseudo-static seismic body force

ABSTRACT In this paper, the seismic stability number of unsupported excavations in cohesive-frictional soil under the influence of pseudo-static seismic body forces is examined. Three-dimensional finite element limit analysis is employed to numerically solve the upper and lower bounded models of unsupported excavations. The results are represented by a dimensionless stability number which is a function of four dimensionless parameters including the excavation aspect ratio, the excavated depth ratio, the soil’s effective friction angle, and the coefficient of horizontal earthquake acceleration. For the first time in literature, the influences of a soil’s effective friction angle and the coefficient of horizontal earthquake acceleration on the mechanisms of excavation failures are examined and discussed. Also presented is a case study to demonstrate the use of the proposed seismic stability number in studying unsupported excavations in seismic risk areas.