Experimental study on rock indentation using infrared thermography and acoustic emission techniques

For better understanding of rock fragmentation mechanism and correlative influence factors under the cutter penetration, a set of two-dimensional wedge indentation tests was conducted. Nondestructive detection techniques, including infrared thermography and acoustic emission, were employed to capture rock damage evolution information. Combined with experimental observations, the cavity expansion model (CEM) theory was adopted to interpret the temperature rise differences for different rock damage zones, and the sizes of these zones were quantitatively determined based on the thermal distribution. It was thought that different thermomechanical coupling mechanisms in different damage zones cause their differences in temperature rise degrees. The quantitative estimation for damage zone sizes indicates the plastic zone and core zone initiate and develop sequentially rather than simultaneously. The main influence factors on rock indentation and damage evolution characteristics were also considered, including rock type, wedge indenter geometry and confining stress. Furthermore, some shortcomings of the classical CEM were discussed through the comparison of indentation pressure and damage zone size between the experimental value and theoretical estimation.