Study On The Influence Of Different Strain Rates On The Mechanical Properties Of Salt Rock

In recent years,with the adjustment of China's energy strategy,the development of underground salt rock energy storage has continued to accelerate.However,during the construction and operation of underground salt rock reservoirs,the salt rocks around the reservoir may be subjected to low strain rate loads under static loads due to the velocity of the cavity,the shape of the cavity,the bias stress,or the injection-production rate.The surrounding salt rocks may be subjected to high strain rate loads due to dynamic loads such as earthquakes,fires,or explosions.Considering the factors that affect the safety of salt rock reservoirs during construction and operation,this paper uses a combination of laboratory tests and numerical simulations to study the effects of different strain rates on the mechanical properties of salt rocks.The main contents and conclusions of the research are as follows:(1)Through the static load compression test under the strain rate of 2×10^-5s^-1-2×10^-3 s^-1,it is found that the peak strength of salt rock increases with the increase of strain rate at low strain rate,but the peak strain decreases gradually.The overall change trend of the stress-strain curve of salt rock under low strain rate was basically the same,but there were differences in the curve change in different deformation stages.The damage degree of salt rock increased with the increase of the strain rate,and had a certain rate correlation.(2)Through the dynamic load compression test under the strain rate of 23.470s^-1-53.516 s^-1,it is found that the peak strength and peak strain of salt rock increase with the increase of strain rate under high strain rate.The overall variation trend of stress-strain curve of salt rock under high strain rate is less affected by strain rate,but there are differences in different compression stages.The degree of salt rock failure increased with the increase of the strain rate,and the time for complete failure of the test piece also decreased.(3)Based on the Particle Flow Code(PFC),the mesoscopic parameters of the salt rock numerical model were calibrated by the results of laboratory tests under static load,and the salt rock numerical model compression test was performed at low and medium strain rates.By monitoring the cracks in the salt rock model,it was found that the total number of cracks increased with the increase of the strain rate,but the overall evolution trend of the cracks was less affected by the strain rate.Based on the study of energy dissipation theory,it was found that the trends of the energy characteristics with strain were basically the same,but there were obvious differences in the energy characteristics at different compression stages.(4)Using particle flow program,a numerical model of salt rock SHPB was constructed and numerically studied.It was found that the peak strength of the salt rock model and the total number of internal cracks increased with the increase of the strain rate at high strain rates.The overall evolution trend of cracks with strain was basically the same,but the crack evolution was different at different compression stages.The crack activity was more intense in the plastic deformation stage and the early failure stage.