Experimental Study On Dynamic Compression Mechanical Properties Of Shale Under Confining Pressure

As conventional sources of oil and gas have dried up,alternative unconventional energy sources(shale gas)have become increasingly popular.In the actual shale gas exploitation project,different impact loads make shale subjected to the impact pressure.Meanwhile,the shale strata in China are buried deep and the rock mass is in a state of complex stress.It is important to study the dynamic mechanical properties of shale under confining pressure.In this paper,the dynamic mechanical properties of shale under confining pressure are studied.The main contents are as follows:(1)Taking the shale gas exploitation in changning county,yibin,sichuan province as the engineering background,this paper selected local shale as the experimental research objective,tested the basic physical and mechanical parameters of shale,ensured the uniformity of specimens,reduced the test error,and provided parameters for the following simulation.(2)The uniaxial SHPB test of shale was carried out,the compressive strength and failure mode of shale under different strain rates were discussed,and the waveform graph of "double wave peaks" under uniaxial compression was determined.The uniaxial dynamic compressive strength had obvious strain rate effect.(3)SHPB test under confining pressure was carried out,and the waveform chart of "single wave peak" under confining pressure was compared and analyzed.Under the same impact pressure,the confining pressure increased,and the dynamic compressive strength and DIF of shale increased.In terms of energy,the specific energy absorption value of shale increases with the increase of strain rate.The incident energy increases with the increase of impact pressure,while the energy utilization rate of rock sample decreases with the increase of incident energy under the same confining pressure.With the same incident energy,the energy utilization rate decreases with the increase of confining pressure.(4)The numerical simulation of dynamic compression of shale under confining pressure is carried out,the parameters of K&C model are determined,and the feasibility of the model is verified by experiments.Through the simulation of SHPB test shale's failure process,it is found that the failure of shale under the uniaxial impact pressure is mainly the tensile failure,and the confining pressure can effectively inhibit the diffusion of shale internal crack.