Dynamic biaxial compressive strength and fracture pattern of concrete with constant confining pressure

The dynamic compressive test of 66 cubic concrete specimens was carried out on the servo static-dynamic triaxial test machine developed by Dalian University of Technology.The effect of strain rate and lateral confining pressure on the dynamic strength and fracture pattern was studied.The lateral confining pressures were kept constantly with 0,30.5%,61.0% and 91.5% of static uniaxial strength respectively and the strain rate varied from 10~(-5)s~(-1) to 10~(-2)s~(-1).It is revealed that the ultimate strength under any biaxial loading state increases with the increase of strain rate.The strain rate sensitivity of concrete tends to decrease with higher lateral confined stress.The enhancement effect of constant confining pressure on ultimate strength becomes weak at high strain rate.A unified formula is suggested to express all the factors affecting the dynamic properties of concrete under biaxial loading state.