Experimental study on re-crushing behaviour of crushed limestone based on acoustic emission location method

The examination of non-uniform deformation and re-crushing characteristics of crushed rock and coal is fundamental to understand porous structure evolution of the caved zone. This paper proposed a new index to evaluate the re-crushing degree of mixed crushed limestone based on an innovative compression-acoustic emission (AE) location method. Results showed that the evolution of the AE characteristic parameters was closely related to the deformation stages. The AE cumulative count and energy curves exhibited different trends corresponding to the initial, linear and plastic compression stages of the stress-time curve, respectively. However, the AE amplitude was mostly lower than 50 dB, and the peak frequency was concentrated at 20-40 kHz during the compression. In addition, the three-dimensional (3D) AE location event energy level (LEEL) was proposed to illustrate particle re-crushing degree. There was layered re-crushing phenomenon in the compression process of crushed limestone. Comparing the quantity and energy level of 3D AE location events in each layer, we discovered that the re-crushing behaviour in the middle layer was the most active, and that in the upper layer was approximately twice than that in the lower layer. High energy level AE location events could significantly influence the evaluation of re-crushing degree.