Seismic soil resistance for caisson design in sand

The exact solution of the passive resistance acting on a caisson foundation due to earthquake-induced loading is important for the seismic design of caissons. In this study, the three-dimensional soil–caisson interaction was taken into account in the determination of the ultimate soil resistance by considering the idealised passive wedge developed in front of a rectangular caisson in sand. A simplified analytical formulation of the seismic passive earth pressure coefficient and its distribution along the wedge height was developed by using the limit equilibrium method and a pseudo-static approach. For the same dataset of input parameters, the seismic passive earth pressure coefficient with a horizontal seismic acceleration coefficient value of 0·2 was approximately 62·7% lower than that for a static condition. The present study emphasises the requirement of correct estimation of the mobilised soil–soil interface friction angle and the height of the passive wedge in order to determine soil resistance. Parametric studies were also carried out to understand the effects of horizontal and vertical seismic acceleration coefficients and the soil–soil interface friction angles. The results of the study compare well with the available experimental data. The solutions proposed should be useful for the seismic design of caissons.