Discrete element modelling of cavity expansion and pressuremeter test

Abstract

Cavity expansion in soil or rock is an important area in theoretical geomechanics because it provides a useful and simple tool for modelling many complex geotechnical problems. This paper describes the simulation of cylindrical cavity expansion and pressuremeter testing of granular materials using the discrete element method (DEM). The Pressuremeter test is one of the most important applications of cavity expansion theory. The theory of cylindrical cavity expansion has been adapted by geotechnical researchers and engineers as the most important interpretation method for self-boring pressuremeter tests in soil and rock. It is also used to describe the soil properties of cone pressuremeter tests. To compare the DEM simulation results with continuum analysis, analytical solutions of large strain expansion of Mohr-Coulomb material are also given. For simplicity, the soil stress-strain behaviour is considered as elastic-perfectly plastic. Some biaxial test simulations using DEM are performed to obtain the basic granular material properties for obtaining cavity expansion analytical solutions based on continuum mechanics. Macro properties of the samples for various input micro parameters are presented and used to obtain the theoretical cavity expansion solutions. The comparison between the numerical simulations and analytical solutions shows good agreement. A range of pressuremeter test simulations of various initial porosities using different particle shapes were conducted. The simulations demonstrated the validity of DEM simulations of the pressuremeter test, providing micromechanical insight into the behaviour.

Keywords:

• discrete element methods
• cavity expansion
• pressuremeter test
• biaxial test