An elastic plastic approach, modeling deformation of dense sand

Abstract

This thesis examines the mechanical behaviour of dense (dilative) sand. The dense sand was tested under high pressure conditions (80 MPa in one dimensional compression and a confining pressure of 7.2 MPa in triaxial testing) and high temperatures (up to 100C). The behaviour of the dilative sand could be successfully described by using elastic plastic concepts. The triaxial testing program used modified equipment from the University of Manitoba's Soil Mechanics Laboratory (larger specimen sizes). The testing methodology followed typical drained triaxial testing methods, but the temperatures and pressures at which the tests were performed where much higher than typical. The 1-D compression testing was performed in a newly designed and constructed test apparatus. The elastic-plastic model Cam Clay was able to capture many of the aspects of the dilative sands behaviour, modifications to the base model were necessary to account for particle breakage at high stress levels and variations in shear stiffness with shear strain. The normal compression line of sand is considered to be defined in the grain crushing region. The isotropic compression testing performed did not reach stress levels high enough to induce grain crushing. A new equation was developed to describe the isotropic compression behaviour of sand prior to reaching the normal compression line. Triaxial testing was performed at three different temperatures to determine the effect of temperature. No consistent effect of temperature was encountered in either isotropic compression or triaxial shear.