(1. State Key Laboratory of Geomechanics and Geotechnical Engineering，Institute of Rock and Soil Mechanics，Chinese Academy of Sciences，Wuhan，Hubei 430071，China；2. School of Science，Qingdao Technological University，Qingdao，Shandong 266033，China；3. Department of Civil Engineering，Logistical Engineering University，Chongqing 400041，China)
Abstract：Loading axial compression and unloading confining pressure tests and simulations of particle flow under different unloading rates have been performed，and effects of unloading rate on unloading failure process of brittle rock have been analyzed by multi-perspective macro-meso methods. The results show that，specimens show shear failure in the macroscopic，but show connective failure plane caused by tensile cracks propagation in the microscopic. The phenomenon of bond energy and strain energy simultaneously show the characteristic of negative growth，which could be known as failure precursor of brittle rock. There are several connective failure planes containing discontinuous joints，obvious secondary shear planes and larger distribution area of tensile cracks under high unloading rates. The growing rate of tensile cracks between peak point and inflection point of axial stress grows as unloading rate increases；there are higher shear cracks under low unloading rate. Growing rate of acoustic emission count rate before failure，count rate value around failure and count rate range after failure depend on unloading rate. An increase of unloading rate could cause bond energy，strain energy and friction energy to increase，but kinetic energy to decrease.
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2016, Vol. 35 
