THE INSTABILITY OF EN-ECHELON CRACKS AND ITS PRECURSORS

Abstract

En-echelon cracks can be divided into two types: left lateral shear and left step or right lateral shear and right step (LL), and left lateral shear and right step or right lateral shear and left step (LR). The conditions of interaction and stability of two en-echelon cracks are analyzed by using the linear elastic finite element method and theory of fracture mechanics. Then, the fracturing process and precursors of the main fracture in the staggered region of en-echelon cracks are studied by a series of rock experiments. It is found that the geometrical factors of en-echelon cracks influence the interaction and instability of faults and precursors of the main rupture.