Stress interactions in cracked media during the closure of prestressed cracks

Abstract

Abstract With the increasing pressure, a crack in a medium will be gradually closed, which is affected by stress interactions. The closing process of parallel cracks under vertical stress is simulated here. The coplanar and stacked cracked models are constructed to analyze the influence of two types of stress interaction on the closing process. The spatial distribution of cracks, demonstrated by numerical experiments, has a significant impact on stress interactions and thus the process of crack closure. The mechanisms underlying the delay of crack closure caused by stress interactions are different for the two models. Furthermore, according to the stress dependence of crack microscopic parameters (crack porosity, aperture, and length of major axis), the process of crack closure can be divided into three stages: the linear deformation stage, the contact stage, and the closure stage. In the first stage, no contact is permitted inside the crack. The shielding effect directly leads to a closure lag, and thus a linear stress dependence of the microscopic crack parameter. In the second stage, the shielding effect determines the increasing rate for the stress dependence of microscopic crack parameters in regularly distributed cracked models. However, for the randomly distributed cracked model, local stress interactions result in the eccentric closure of cracks, and thus the crack closure lag. In the last stage, the crack is closed and stress interactions disappear both in the regularly and randomly distributed models.