A Pore Pressure Equation from Anisotropic Elastoplastic Model and Its Application

A pore pressure equation derived from an anisotropic elastoplastic model is presented here and used to study the effect of anisotropy on pore pressure development for clays. By incorporating the Sekiguchi-Ohta Stress Ratio eta* and Xing's failure equation into the Modified Cam Clay model, an anisotropic elastoplastic model is built, which can account for K0 consolidation induced anisotropy and anisotropic failure in the pi plane for clays. A pore pressure equation is derived from the model in which the effects of Lode's angle and rotation of principal stresses sigma1 and sigma3 are considered. This equation is used to investigated the pore pressure development induced by rotation of the Lode's angle and stress axis in two situations - clay samples under tri-axial stress conditions and plane-strain anisotropic clay ground beneath a strip load. The results show that the pore-water pressure change induced by the Lode's angle rotation in the anisotropic clay ground is negligible, however, the corresponding change induced by the rotation of principal stress axis is significant for the soil right beneath the edge of the load, especially at a relatively shallow depth.