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| Effects of the unloading rate on dynamic characteristic and failure modes of rock under high static loads |
| WANG Chun1，2，3，CHENG Luping1，TANG Lizhong2，WANG Wen1，3，LIU Tao2，WEI Yongheng2，SHEN Wenlong1 |
| (1. School of Energy Science and Engineering，Henan Polytechnic University，Jiaozuo，Henan 454000，China；2. School of Resources and Safety Engineering，Central South University，Changsha，Hunan 410083，China；3. The Collaborative Innovation Center of Coal Safety Production of Henan，Henan Polytechnic University，Jiaozuo，Henan 454000，China) |
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Abstract In order to study effects of the unloading rate on the dynamic characteristics and failure modes of deep rock，the improved SHPB test system combined with dynamic and static loadings，which can simulate the mechanical environment of deep rock excavations subjected to impact disturbance during high static unloading process，was used to carry out the frequent disturbance test under high axial pressure and unloading. The samples were applied by a complete cycle loading. Specifically，a sample was firstly applied with a given axial load referring to the uniaxial compressive strength of deep serpentine，then unloaded till to 50% of the axial load at a certain rate and at the moment，an impact load of 0.4 MPa was exerted，and finally the unloading process terminated. The test results show that the dynamic stress-strain curve of rock and its envelope have a stage of nonlinear development following a short straight line stage，which indicates that plastic deformation of rock specimen plays a dominate role during impact disturbance and unloading. The increase of the unloading rate leads to obvious delaying effect of rock specimen on the impact load，resulting in an increase of rock?s mean strength and the cumulative number of impact disturbance，and causing the interconvertible phenomenon of brittle and ductility. With increasing the pre-axial stress and the unloading rate，the fragmentation of damaged rock mass increases，and they lead to tensile and shear failures，respectively.
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2019, Vol. 38 
