Study On Dynamic Characteristics Of Mudstone And Sandstone Under Impact Load

It is difficult to evaluate the mechanical properties of deep rock mass in complex stress environment by experience.In addition,it is often subjected to the impact load of four sides.The rock is subjected to the impact of the impact load.Under this dynamic load,the deformation and failure of rock are all related to time.This problem has become a major problem in deep rock engineering,which attracts many researchers to study the dynamic mechanical properties of rock.Deep well coal mining is a very good engineering example.In order to carry out the blasting excavation of rock roadway and the supporting of surrounding rock more effectively,it is necessary to study the dynamic performance of rock under the impact load.the dynamic mechanical properties of common mudstone and sandstone under the impact load are studied by using the diameter 50 mm separation Hopkinson test device.The dynamic mechanical properties of rock samples were tested by changing loading rate.Stress strain,fragmentation and energy dissipation of two kinds of rocks under the impact test condition are mainly studied.The sample is taken from underground tunnel of a coal mine in Huainan mining area.Through the shock test and analysis of the test results,it is shown that in the test strain rate range,with the impact velocity of the bullet increasing,the greater the impact kinetic energy,the smaller the fragmentation of the two rock specimens.With the increase of strain rate,the dynamic yield strength of mudstone and sandstone increases obviously,while the elastic modulus of sandstone remains constant and the elastic modulus of mudstone increases gradually.The dynamic uniaxial compressive strength of the two kinds of rock increases exponentially with the increase of strain rate,showing a strong strain rate effect.The dissipation energies of the two rocks are linearly related to the strain rate,while the crushing size is negatively linear with the strain rate.What needs to be noticed is that the common cracks first appear near one end of the entrance bar,then extend to the vertical to carry out the cracks,and then the mudstone will appear obvious transverse cracks.