THE INITIATION OF FLOW IN ANTIGRANULOCYTES MATERIALS

The effects of rotation of principle stress directions on the initiation of flow in particulate materials have been studied experimentally in the Directional Shear Cell. Four materials were tested: sand, coal, kaolinite and bentonite. A range of dampness from dry to full saturation was covered. For sand and coal, the rotation of principal stress directions causes initiation of flow at much lower stress ratios than monotonic loading and the reduction is related to the amplitude of rotation. There were strong indications that similar effects exist in saturated and nearly saturated kaolin but further work is required. Two simple quantitative stress dilatancy relationships are related to basic mechanisms of energy dissipation and have been strongly confirmed in a wide range of experimental conditions. Monotonic shearing of granular material after shear under cyclic rotation of principal stress directions has shown large gains in shear strength and stiffness which are not related to any density change under cyclic loading.