Experimental and numerical studies of a three-dimensional bonded contact model of cemented granular soils
Nazanin Mahbubi Motlagh, Ahmad Mahboubi, Ali Noorzad
Abstract
The simulation of the mechanical behavior of cemented granular material using the discrete element method depends heavily on the bonded contact model. In this study, a three-dimensional discrete element method bond contact model is presented and validated by a series of experimental micromechanical tests on ideal bonded particles (cement-bridged aluminum spheres) subjected to different loading modes. The model uses the cement content and water/cement ratio as parameters affecting the behavior of cemented specimens. The empirical relations between the bonded contact model properties—bond geometry, bond strengths (tensile, compressive, shear, rolling, and torsional strengths) and bond stiffnesses—cement content, water/cement ratio, bonded particle diameter, and particle distance are determined. Discrete element method simulations of drained triaxial tests on cemented specimens are conducted with different cement contents (1, 2, and 3%) and water/cement ratios (0.3, 0.6, 0.9, 1.2, and 1.5) under various confining pressures (100, 300, and 500 kPa) to evaluate the capability of the proposed bonded contact model to predict the mechanical behavior of cemented soils. A comparison between numerical and experimental test results revealed that the bonded contact model can capture the primary mechanical behaviors of these materials (strain softening and dilatancy) with reasonable accuracy by considering two parameters (cement content and water/cement ratio). Microscopically, it is observed that the increase in cement content and the reduction in water/cement ratio increase the maximum inter-particle force magnitude. The number of bonds formed between particles at the beginning and end of the test is affected by the cement content and water/cement ratio.