S. Utili
Dept. of Civil Engineering, Strathclyde University, Glasgow, United Kingdom
R. Nova
Dept. of Civil Engineering, Politecnico di Milano, Milan, Italy
Keywords: distinct element method, bonded geomaterials, cohesive frictional materials
ABSTRACT :
A new contact bond model based on the Mohr-Coulomb failure criterion has been implemented in PFC2D to reproduce the behaviour of frictional cohesive (c, φ) geomaterials. According to this model, the bond strength can be clearly divided into two distinct micromechanical contributions: an intergranular friction angle and a cohesive bond force. A parametric analysis has been run to validate the proposed model and to calibrate the micromechanical parameters. Simple relationships between the macromechanical strength parameters (c, φ) and the corresponding micromechanical quantities have been obtained so that they can be used to model geotechnical boundary value problems with the DEM without need of further calibration.
1 Introduction
In recent years, some authors used DEM to reproduce the behaviour of bonded grains in 2D. (Potyondy and Cundall, 2004), used the parallel bond model offered in PFC to study the brittle behaviour of granites under compressive loading. (Jiang et al., 2006) introduced a bond model in the code NS2D to study the behaviour of bonded granulates. (Delenne et al., 2004) performed experimental tests on pairs of aluminium rods glued by an epoxy resin to deduce micromechanical relationships between relative displacements and forces at the contact between rod pairs. In all these cases the bond between two particles possesses a finite width and therefore the particles exchange not only a normal and tangential force but also a moment at their contact point. As a consequence, the number of micromechanical parameters requiring to be calibrated becomes larger than the case of unbonded particles. In the present paper, a model for cohesive frictional geomaterials where particles only exchange forces at the contact points is proposed. Therefore, only one additional micromechanical parameter is required to pass from the unbonded case to the bonded one. The paper is divided into three parts. In section 2 the procedure used to run the numerical biaxial tests will be illustrated. In section 3 it will be shown the calibration of PFC parameters to reproduce the behaviour of frictional cohesionless geomaterials while in section 4 it will be shown the calibration for frictional cohesive geomaterials.
0 comments:
Post a Comment