Long-Term Strength of Porous Geomaterials by a Micromechanical Model considering Alternate Wetting and Drying Condition

Jin Zhang,Tao Ni,Shirong Fu,Chong Shi,Bei Han,Feng Xiong

doi:10.1155/2021/6617453

Abstract

This study is devoted to determining the long-term strength of porous geomaterials under alternate wetting and drying condition by statical shakedown analysis. In the framework of micromechanics of porous materials, Gurson’s hollow sphere model with Drucker-Prager solid matrix is adopted as the representative volume element. The effects of alternate wetting and drying are considered as variable water pressure imposed on the inner boundary surface of the unit cell. The cyclic responses are separated as a pure hydrostatic part under compressive/tensive loads and an additional deviatoric part to capture shear effects. The reduction of the long-term strength due to inner water pressure is observed by the illustration of obtained macroscopic criteria with respect to various load parameters. In addition, the accuracy of the analytical solution is also verified by comparing to the results of FEM-based step-by-step computations.

Highlights

Variable loadings exist widely in engineering structures, such as slops, offshore platform foundations, and pavements [1,2,3]
= Σm/Σeq for all the cyclic load path remains constant in a single cycle, which is implemented in Abaqus by the means of multipoint constraint subroutine (MPC) satisfying the imposed uniform velocity field boundary condition
In general (Figures 9–11), an accordance between the results obtained by the proposed macroscopic criterion and the step-by-step computations can be observed, indicating that the established criterion has the ability to predict the long-term safety of the considered porous geomaterials under hydromechanical variable loads

Summary

Introduction

Variable loadings exist widely in engineering structures, such as slops, offshore platform foundations, and pavements [1,2,3]. The obtained macroscopic criterion by homogenization is expected able to predict the long-term strength of porous geomaterials under alternate wetting and drying condition. A micromechanic-based hollow sphere representative volume element (RVE) of porous geomaterials is firstly introduced Using this model, we recall a macroscopic strength criterion proposed by Guo et al [29], which can describe the plastic compressibility and asymmetric behaviors between tension and compression of the studied materials at the macroscale. This section is devoted to calculate the strength reduction of porous geomaterials subjected to variable loadings, comparing to the homogenized yield criterion (Equation (10)). Combining the shakedown condition (14) and the microscopic stress field (20), the following equations at the vertices can be obtained at the shakedown limit state (the equality is reached): ðγC0

KðaÞ C1 ξ2ðθÞ

Numerical Verification by Step-by-Step FEM Computations

Conclusion