Experimental investigation on infrared radiation features of fracturing process in jointed rock under concentrated load
International Journal of Rock Mechanics and Mining Sciences
In case of earthquakes and crustal movement, the concentration of impounding load over a large region of crust can cause disturbances to the stratum. In order to quantitatively investigate crack initiation, propagation and coalescence processes of jointed stratum based on thermal variations caused by concentrated load, a series of indentation tests were performed on jointed granite specimens, failure process was respectively recorded by synchronized digital image correlation system and infrared camera. Then, strain and infrared radiation temperature of mixed shear-tensile and tensile conical crack were analyzed. In the initiation process, experimental results indicate that the abnormities in the temperature concentration factors are caused by the frictional-thermal effect for mixed mode crack and the thermoelastic effect for tensile mode crack. Subsequently, in the propagation process, these two cracking types followed newly proposed criteria, namely, the maximum temperature gradient criterion for mixed mode crack and the minimum temperature gradient criterion for tensile mode crack. In addition, the intensity of temperature concentrations in crack initiation stage and coalescence stage are more pronounced than that of crack propagation stage. The new findings from the infrared radiation temperature distributions provide some fundamental references for geophysical prospecting in jointed rock mass.
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