Impact compression test of rock material under passive confining pressure conditions

In order to study the dynamic mechanical properties and failure behaviors of coalmine rock material under passive confining pressure condition,a 50 mm variable cross-section split Hopkinson pressure bar(SHPB) apparatus was used to conduct impact compression tests in different loading rates under 45 # steel sleeve constraint condition.The test results show that the ductility and damage resistance of rock material increase under passive confining pressure.The axial failure stress of rock specimens under passive confining pressure is about 1.2 times as large as that without passive confining pressure.The failure strain is also about 1 to 2 times bigger than that without passive confining pressure.The radial stress increases with the growing of axial stain.The failure modes for rock specimens with or without passive confining pressure are different,and that with passive confining pressure is a compression-shear mode.