Three-dimensional constitutive model for cemented sands based on micro-mechanism of bond degradation

Based on the framework of breakage mechanics for geological materials and the critical-state soil mechanics, a three-dimensional (3-D) constitutive model for cemented sands is proposed following the research idea for macro- and micro-mechanical soil mechanics. A yield surface for reconstituted sands is improved for the cemented sands by enlarging the surface size. To consider the behaviors of shear strength in the 3-D space, the Lade-Duncan strength criterion, validated by simulations of 3-D distinct element method (DEM), is used as the critical-state strength surface. A degradation evolution for bond is obtained from 3-D DEM specimens based on the micro-mechanics theory for cemented materials and the simulated results of DEM. By introducing the degradation evolution for bond, the hardening law and flow rule for reconstituted sands are modified and applied for cemented sands. The proposed model is preliminarily verified by predicting the mechanical behaviors of artificially cemented sands in the conventional triaxial compression tests and true triaxial tests with constant mean stress.