分级循环荷载下裂隙岩石疲劳破坏特性与能量演化机制OA北大核心CSTPCD

The crack propagation mode,fatigue deformation characteristics and energy evolution pattern of cracked rock under graded cyclic loading are of great significance to the safe construction and operation of underground engineering.Conventional splitting test,graded cyclic load test and non-contact deformation measurement test were carried out considering the crack angle,crack number and distribution.The failure characteristics and dynamic elastic modulus were analyzed,and the relationship between axial irreversible deformation and fatigue life was studied.From the perspective of energy,the total absorbed energy,released strain energy and dissipated energy in the failure process were calculated,and the relationship between energy evolution and the response of crack propagation mode was analyzed.The results show that:(1)The fatigue deformation of rock can be divided into the initial deformation stage,stable stage and the accelerated failure stage,and the hysteretic loop curve presents the characteristics of"thin-dense-thinness".The dynamic elastic modulus of every 200 cycles is analyzed and that of the second loading stage is strengthened.In addition,the dynamic elastic modulus decreases after the third loading stage.(2)The total absorbed energy,dissipated energy and elastic energy all showed an upward trend.The total absorbed energy increased slowly,and the growth rate gradually slowed down with the increase of cycles.The dissipated energy increases rapidly after entering the failure stage,but the elastic strain energy does not change obviously,and the dissipated energy is more in the middle dip angle.(3)During failure process,wing cracks and inclined secondary cracks are generated,and the interaction and merger of the cracks result in continuous plastic strain accumulation and small particle debris,which is different from the brittle failure mechanism under static load.