Propagation Of Tensile And Compressive Stress Wave In Cracked Rock Masses And Dynamic Response Of Underground Openings

In rock masses with a large number of discontinuous structures,the geometric forms and development levels of crack are different.Among them,non-persistent crack is more common in actual engineering.Dynamic disturbances in rock mass engineering usually propagate in the form of stress waves,After the propagation and attenuation of cracked rock mass,the tensile and compressive stress waves act on the rock underground opening,which will lead to the dynamic response,damage and failure of the surrounding rock of underground opening.However,the action law and mechanism of tensile stress wave and compressive stress wave propagating across the nonpersistent crack is still unclear,the dynamic response of rock underground engineering under the action of tensile and compressive stress waves is not fully studied.Therefore,it is of great engineering significance and academic value to study the propagation of tensile and compressive stress wave in cracked rock mass and the dynamic response of underground opening.In order to explore the influence of non-persistent crack on the propagation of stress wave,the propagation of tensile and compressive stress waves across nonpersistent crack is studied by using SHTB and SHPB instruments respectively.The effects of crack persistence and stress amplitude on transmission and reflection coefficients and energy transmission and reflection were compared and analyzed.Combined with the actual rock blasting engineering,numerical simulation is carried out to study the influence of tensile and compressive stress waves on the dynamic response of underground opening,the influence of crack persistence,stress wave amplitude and crack number on the distribution of stress field,deformation of crack and PPV of underground opening was studied.The results show that:(1)SHTB and SHPB were used to study the propagation of tensile and compressive stress waves across non-persistent crack,and the influence of crack persistence and stress wave amplitude on the transmission and reflection coefficients and energy transmission and reflection were discussed.The results show that the amplitude of tensile stress wave have obvious influence on the transmission and reflection coefficient and energy transmission and reflection.The amplitude of compressive stress has no obvious effect on the transmission and energy transmission,but has great influence on the transmission and energy transmission and reflection of filled crack;The crack persistence has a great influence on the transmission and reflection coefficient and energy transmission and reflection.(2)Based on the test results,the transmission and reflection coefficient and the energy transmission and reflection of tensile and compressive stress waves across nonpersistent crack and filled cracks were compared and analyzed.The results show that the propagation of tensile stress wave is more affected by the change of crack persistence and stress wave amplitude than those of compressive stress wave.The changing trends of transmission and reflection coefficients and the energy transmission of tensile stress wave are opposite to those of compressive stress wave.(3)Combined with the actual rock blasting engineering,the finite element numerical simulation was carried out to explore the influence of crack persistence,stress wave amplitude and crack number on the rock stress field distribution,fracture deformation and underground chamber PPV.The results show that the "shuttle" distribution of stress field in rock mass is scattered due to the crack failure,and the more the number of fractures is,the more complex the distribution of stress field is;The deformation of non-persistent crack is not related to the degree of crack persistence,but related to the amplitude of stress wave.Compared with the compressive stress wave,the PPV of the surrounding rock of the underground opening under the action of tensile stress wave is smaller.