THE EFFECT OF FRICTION ON SIMULATED DYNAMIC FRACTURING OF ROCKS

Abstract
During underground nuclear tests, rocks may fail by plastic yielding, which limits shear strength, or by tensile fracture, wherever maximum principal stress exceeds tensile strength. A third mode of failure exists due to friction along closed fractured surfaces. There, friction affects slipping and can thus limit stress. In this paper, we study the effect of fiction on the simulated dynarnic response of rocks to underground nuclear explosions. The coefficient of friction is the ratio of total shear stress applied to a closed fracture surface to normal applied compressive total stress. At low coefficients of friction, the evolving stress field tends to be weakened by fictional slip, which also eases closing of fractures. At high coefficients of friction, the stress field tends to be strengthened, where fractures have closed, but remains weak, where fractures are left open.