| The main objective of this work is to develop a discrete element model for a bonded granular assembly to simulate rock behavior under uniaxial compression. The model is represented by an assembly of 2-dimensional discs. Detailed algorithms are implemented in the computer program BOND, which is modified, edited, and compiled specially for this work.; The model of a bonded granular assembly is created based on the general structure of sandstone, which is granular in nature and contains cement among particles. In this model, particles and bonds are treated separately. Particles, represented by discs in the model, are rigid bodies, which can deform but not be broken. Particles are able to translate as well as rotate. Bonds, formed conceptually at original particle contact points, can deform and break in the model. The behavior of particle contacts and bonds is controlled by a bond contact model and a slip contact model. The bond contact model shows that bonds can be broken by either a tensile force or a shear force, using the criteria of bond tensile strength and bond shear strength. At contacts without bonds, the slip contact model is active. The slip contact model shows that slip can occur when particle shear contact forces exceed Coulomb strength criteria. Bond breakage is irreversible while particle contacts can be disintegrated and then regenerated.; Both particle contact forces and bond forces vary linearly with deformation. Stiffness is calculated separately for particle contact and bond based on Dvorkin's formulation. In order to save computation time for the main algorithm of the discrete element method, an approximate formula is derived and implemented in the computer program BOND to calculate contact normal stiffness for particles, bonds, and the system from particle and bond properties.; The numerical simulation of the bonded granular assembly under uniaxial compression is conducted using a circular assembly of 1000 discs. Real rock parameters are used in the simulation. The assembly is calibrated using Navajo sandstone mechanical properties that are found in the literature. The stress-strain relationship from numerical simulation results shows that rock has brittle type failure under uniaxial compression. (Abstract shortened by UMI.)... |
