AN ELASTOPLASTIC CONSTITUTIVE MODEL OF SANDS CONSIDERING CYCLIC ROTATION OF PRINCIPAL STRESS AXES
TONG Zhaoxia1，2，ZHANG Jianmin2，ZHANG Ga2
(1. School of Transportation Science and Engineering，Beihang University，Beijing 100191，China； 2. State Key Laboratory of Hydroscience and Engineering，Tsinghua University，Beijing 100084，China)
Abstract：The deformation behavior of sands under cyclic rotation of principal stress axes can be concluded as follows based on the current test results. Firstly，the volumetric strain induced is increased with the increase of cycles number，yet its increase rate is lowered with its progressive accumulation. Secondly，the hysteretic loop is produced for the shear stress and strain components. And the unclosed hysteretic loop tends to be closed with the increase of rotation cycle numbers. Thirdly，the obvious non-coaxiality between directions of the plastic strain increment and stress shows segment characteristics. Finally，the effects of the intermediate principal stress parameter are significant. The accumulation rate of the volumetric strain is increased with the increase of the intermediate principal stress parameter under otherwise identical conditions. Based on the above physical fundamentals of sands subjected to cyclic rotation of principal stress axes，a new cyclic elastoplastic constitutive model for saturated sands aiming at describing the deformation behavior of sands due to cyclic rotation of principal stress axes is developed. And its effectiveness under the complex stress paths including cyclic rotation of principal stress axes is verified by comparison of simulation model and test results；and it is shown that the proposed constitutive model is capable of predicting reasonably the developments of strain components and the volumetric strain in various conditions including principal stress axes rotation.
