Experimental study on fracture behaviors of hard rock under dynamic disturbance with different pre-static loads
GONG Fengqiang1，2，3，ZHANG Le1，LI Xibing1，3，LUO Yong1
(1. School of Resources and Safety Engineering，Central South University，Changsha，Hunan 410083，China；2. State Key Laboratory for Geomechanics and Deep Underground Engineering，China University of Mining and Technology，Xuzhou，Jiangsu 221008，China；3. Institute of Mechanics for Engineering Materials，Advanced Research Center，Central South University，Changsha，Hunan 410083，China)
Abstract：In order to investigate the variation of fractures of pre-static loaded hard rock under the different dynamic disturbance，the fracture toughness tests of sandstone were carried out on three point bending specimen with a straight crack in the center of the red sandstone(SCB) using the electro hydraulic servo testing machine Landmark MTS. Four pre-static load levels(60%，70%，80% and 90% of conventional static fracture load) were selected. The dynamic disturbance tests were conducted by using the sine wave loading. The amplitude of loading were 40%，30%，20% and 10% of the static fracture load and the loading frequency were 1，10，20，30，40 and 50 Hz respectively. Compared with in the conventional static fracture tests，the fracture toughness of rock under different pre-static loads decreased and it decreased linearly with the increase of the disturbance frequency. However，the toughness decreasing effects under the different static pre-loadings are different. The higher the pre-static level，the greater effect of the toughness decreasing. Compared with the conventional fracture displacement，the fracture displacement under pre-static loadings decreased as a whole. The concentrated distribution of disturbance induced fracturing point was found. The fracturing point occurred in the loading stage above the pre-static level when the pre-static load level is less than 90%，while the fracture point occurred in the unloading stage above the pre-static load level when the level of pre-static load is 90%. With the increase of disturbance frequency，the fatigue life span increased firstly，then decreased and finally increased again with an overall trend of increasing. No obvious correlations between the time of fracturing failure，the pre-static load level and the disturbance frequency were found. The cracking effect is about optimal when the disturbance frequency is 10 Hz.
宫凤强1，2，3，张 乐1，李夕兵1，3，罗 勇1. 不同预静载硬岩在动力扰动下断裂特性的试验研究[J]. 岩石力学与工程学报, 2017, 36(8): 1841-1854.
GONG Fengqiang1，2，3，ZHANG Le1，LI Xibing1，3，LUO Yong1. Experimental study on fracture behaviors of hard rock under dynamic disturbance with different pre-static loads. , 2017, 36(8): 1841-1854.
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2017, Vol. 36 
