Influences of Anisotropic Undrained Shear Strengths of Clays on Pullout Capacity of Planar Caissons

Abstract

In this paper, the pullout capacity of planar suction caissons in anisotropic clays is investigated by the lower bound (LB) and upper bound (UB) finite element limit analysis (FELA), where Anisotropic Undrained Shear (AUS) failure criterion is associated with the analysis. The strengths of natural clays are conceivable to be anisotropic due to the characteristics of unequal shear strengths obtained from triaxial compression and extension tests. In the AUS failure criterion, there are three anisotropic undrained shear strengths obtained from triaxial compression, triaxial extension, and direct simple shear. Other failure criteria for ideal isotropic materials may be unfortunate to capture these anisotropic shear strengths since those models consider only a single undrained shear strength. New solutions of the pullout capacity of planar suction caissons in anisotropic clays are first-time derived based on three main dimensionless parameters, which are the ratio of depth to width of caissons, adhesion factor, and the ratio of undrained shear strength obtained from triaxial compression and triaxial extension. The pullout capacity factor affected by these parameters is also discussed in the paper to portray the influence of strength anisotropy of clays. The solutions to this problem can be used as design charts for general design purposes.