Study On The Law Of Stress Wave Propagation And Energy Transfer In Different Jointed Rocks

In this paper,based on the analysis of discontinuous deformation theory of joints and the time domain recursion method,the propagation equation of stress wave perpendicular incident into multiple parallel joints is derived by mathematical deduction,and the transmission coefficient and energy transfer coefficient of stress wave in jointed rock mass are obtained.Based on SHPB test principle and requirement,similarity theory and statics test,the physical and mechanical mix ratio and parameters of the model material were obtained.Using the improved SHPB test device,the stress wave intensity is controlled by changing the pressure of the bullet firing device,and the initial ground stress on the rock specimen is changed by pressurizing the axial confining pressure device.Considering the influence of the number of joints on the propagation law of stress wave,the specimens with no joints,single joints,double joints and triple joints were designed and fabricated respectively.In the one-dimensional dynamic load test,the SHPB test device is used to carry out one-dimensional dynamic load impact test on rock joints.The following conclusions are drawn :(1)With the same impact pressure,the transmitted stress wave coefficient decreases gradually with the increase of the number of joints.When the impact pressure is 0.2MPa,0.25 MPa,0.3MPa,0.35 MPa and 0.4MPa,and the number of joints increases from 0 to 3,the amplitude of transmitted stress wave decreases by 74.54%,63.13%,52.27%,41.83% and 38.63%,respectively.The transmission coefficient of onedimensional stress wave in unjointed rock decreases with the increase of impact pressure.When the number of joints is 1?3,the transmission coefficient of onedimensional stress wave increases first and then decreases with the increase of impact pressure.(2)Under the same impact pressure,the increase of the number of joints will lead to the decrease of the stress wave energy transfer coefficient.When the impact pressure is 0.20 MPa,0.25 MPa,0.30 MPa,0.35 MPa and 0.4MPa,and the number of joints increases from 0 to 3,the energy transfer coefficient decreases by 95.1%,88.5%,83.3%,74.7% and 70%.With the increase of impact pressure,the energy transfer coefficient in unjointed rock and single jointed rock decreases gradually.The stress wave transfer coefficient increases first and then decreases with the increase of impact pressure in double and triple joint rock masses.In three-dimensional movement combination loading experiment,using the improved SHPB experiment device,on the specimen containing different Numbers of parallel joints under the preload of impact test,draws the following conclusions:(1)the confining pressure is constant,with the joint quantity increase gradually,onedimensional stress wave transmission coefficient are presented in the joint rock decreases gradually.When the confining pressures are 2MPa,4MPa,8MPa and 12 MPa,the amplitude of transmitted stress wave decreases by 48.64%,37.43%,32.27% and42.02%,respectively,when the number of joints increases from 0 to 3.When the impact pressure and axial pressure are constant and the confining pressure increases from2 MPa to 4MPa,the transmission coefficient of jointing rock shows an increasing trend,the increasing amplitude is 3.56%,6.00%,7.73% and 26.16%,respectively.When the confining pressure increases from 4MPa to 12 MPa,the transmission coefficient of jointing rock shows a decreasing trend.The reduction rates were 37.80%,32.46%,28.77%and 55.03%,respectively.(2)With the same confining pressure,the energy transfer coefficient of stress wave gradually decreases with the increase of the number of joints.When the confining pressure is 2MPa,4MPa,8MPa and 12 MPa,and the number of joints increases from 0 to 3,the energy transfer coefficient decreases by 68.20%,56.67%,48.19% and 56.50%.When the confining pressure increases from 2MPa to12 MPa,the energy transfer coefficient of joined-rock firstly increases and then decreases.In SHPB experiment was carried out for different joint rock impact test,the time history curve,peak stress,the stress wave transmission coefficient and the energy transfer coefficient of four Angle analyzes the test results,it is concluded that the stress wave in the joints and the propagation rules of rock specimen and energy transfer law of the blasting excavation of geotechnical engineering has important theoretical guidance and practical significance.