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Abstract In order to study the free charge migration law of different types of coal and rock samples during the process of tensile failure，the charge monitoring system for coal and rock tensile instability and failure is developed under the frame of the Brazil disk splitting test. The mechanical characteristics and free charge migration law are obtained through the real-time monitoring process of sandstone，mudstone and coal samples during tensile instability and failure. The results show that there exist free charges during the tensile process of coal and rock mass. Charge signal abnormal area is corresponding to the stress mutation process in the samples splitting test；and the free charges produced by coal is richer than that produced by sandstone and mudstone during tensile failure. Compared with sandstone and mudstone，the residual strength of coal after fracture still makes the charge signal have larger fluctuation. Charge induction law is different between tensile and compression failure of coal and rock. One of the important reasons for the abnormal charge signal is the damage localization caused by crack propagation under the tensile stress during the tensile instability and failure of coal and rock mass.
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Received: 18 December 2012
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2013, Vol. 32 
