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| STUDY OF DYNAMIC MECHANICAL CHARACTERISTIC OF SANDSTONE SUBJECTED TO THREE-DIMENSIONAL COUPLED STATIC-CYCLIC IMPACT LOADINGS |
| JIN Jiefang1，LI Xibing2，ZHONG Haibing1 |
| (1. School of Architectural and Surveying Engineering，Jiangxi University of Science and Technology，Ganzhou，Jiangxi 341000，China；2. School of Resources and Safety Engineering，Central South University，Changsha，Hunan 410083，China) |
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Abstract Cyclic impact tests on sandstone under different axial and confining pressures are conducted with a modified three-dimensional split Hopkinson pressure bar(SHPB)，in order to analyze the impact resistance of sandstone with cyclic impact number and to research the effect of axial and confining pressures on dynamic fatigue mechanical properties. Confining pressures are set as 4，8，10 and 12 MPa，and four levels of axial static stresses are 49，84，105 and 125 MPa，respectively. Incident waves in input bar are approximately constant，and incident energy is 230 J. The results show that total cyclic impact number will decrease with the increase in axial stress when the confining pressure is constant. The total cyclic impact number has an increasing trend with the increasing confining pressure when axial compression is constant. With the increasing cyclic impact number，dynamic peak stress，deformation modulus at loading stage and elastic strain decrease，whereas dynamic peak strain and residual strain increase. Rock dynamic peak stress has a good negative linear correlation with average strain rate. When the confining pressure is constant，the absolute values of linear-fitted slope of dynamic peak stress and average strain rate increase gradually with the increase in axial stress；and when the axial stress is constant，the bigger the confining pressure is，the smaller the absolute values of linear-fitted slope is. Decreasing axial compression or increasing confining pressure is able to improve rock resistance to cyclic impact loads when the rock is under three-dimensional static stress.
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Received: 13 August 2012
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2013, Vol. 32 
