SPLIT HOPKINSON PRESSURE BAR TEST AND NUMERICAL ANALYSIS OF SALT ROCK UNDER CONFINING PRESSURE AND TEMPERATURE

A special split Hopkinson pressure bar(SHPB) under confining pressure and temperature,triaxial static confining pressure and temperature split Hopkinson pressure bar(TSCPT-SHPB),is designed.The uniaxial dynamic mechanical performances of salt rock with the confining pressures ranging from 5 to 25 MPa were studied experimentally and numerically.The salt rock under the condition of temperature ranging from 40 ℃ to 80 ℃ and the confining pressure from 0.0 to 0.5 MPa was also tested with the TSCPT-SHPB.The influences of the confining pressure and strain rate on the dynamic increasing factor(DIF) of axial compressive strength of salt rock and the effects of the temperature and confining pressure on the dynamic mechanical properties of salt rock were analyzed.It is demonstrated that:(1) The effect of confining pressure on the ductility of salt rock is tremendous under dynamic loading.(2) The salt rock is a rate-dependent and temperature sensitive material;and its maximum dynamic compressive strength increases as the strain rate increases;while the peak dynamic compressive strength of salt rock decreases as the temperature increases under the high strain rate of 400 s-1.It is noted that the increase of the maximum dynamic compressive strength under low confining pressures is more obvious than that under high confining pressures.(3) The approximate expression for the effect of confining pressure and strain rate on DIF of salt rock was presented;and the relationship between peak confining strength and temperature under the high strain rate of 400 s-1was also obtained from the test data.The experimental results by the TSCP-SHPB were validated by numerical simulation,in which the modified Drucker-Prager model and its experiment-based parameters were used.