Abstract: Rock burst is a geological disaster under high stress environment excavation.Unloading test is done under different confining pressures loading and gradient on top loading-unloading on one sided by the large size of rock specimens.The strain of each measuring point inside of the test specimen is collected,combing with the macroscopic damage phenomenons of rock burst,the rock burst properties of brittle rock under different confining pressure unloading conditions is analyzed.The test results show that:the failure model of brittle rock after rock burst is affected directly by the different confining pressures caused by specimen unloading test;the initiation critical crack point during the rock burst process located in specimen unloading surface is caused by the tensile failure of the middle of specimen unloading surface firstly,then caused by the rock compression failure of the upper and lower of specimen unloading surface;the vertical strain value of the specimen point under the high confining pressure environment is larger than the value under the low confining pressure environment at the rock burst transient;the specimen rock burst intensity caused under high confining pressure loading and unloading path is relatively large.

Key words: Brittle rock, Unloading pressure, Stress gradient, Rock burst properties