Abstract

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 mechanical loading, a series of indention tests were performed on granite specimens. In the experiment, fracture process and resulting infrared radiation fields of specimens were respectively recorded by synchronized digital image correlation system and infrared camera. Then, thermal characteristics of mixed shear-tensile and tensile conical crack were analyzed. Experimental results indicate that the highlighted temperature localization is mainly caused by shear deformation within the localized fracture process zone. It is shown that in the initiation process, 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 crack 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. These thermal effects strongly correlated with the stress states in the cracking process. The new findings from the infrared radiation temperature distributions improve our understanding of fracturing process of rock mass. Furthermore, it will provide some fundamental references for geophysical prospecting in jointed rock mass.