Effect of Particle Size on the Energy Evolution of Crushed Waste Rock in Coal Mines

Excerpt

Coal mine waste rock is an inevitable product of driving entries and the exploitation and washing of coal resources, (Fan et al. 2014; Yossifova 2014). During the extraction process, the overlying strata gradually sink and collapse gradually, forming a caving zone, a fractural zone and a bending zone above the coal seam (Peng 2008; Adhikary and Guo 2015; Basarir et al. 2015). Given the overlying stress, the caving waste rock is compacted and develops another balanced state. The waste rock produced by driving entries and washing of coal typically accumulates on the surface, which may result in landslides and environmental pollution (Brake et al. 2001; Hughes et al. 2007; Adibee et al. 2013). Considering the large dam of accumulated waste rock on the surface, some scholars have proposed a processing method for filling the gob area with broken waste rock to support the overlying strata (Junker and Witthaus 2013; Guo et al. 2014; An et al. 2016). This method can both effectively control the overlying strata deformation and dispose of the waste rock (Zhang et al. 2015). Most importantly, dynamic hazards caused by hard roofs, such as rock bursts, coal and gas outbursts and shockwaves (Li et al. 2016), can be prevented by filling the gob area with crushed waste rock. When a hard roof sinks, deforms and exerts stress on the crushed waste rock, the compaction of the crushed waste rock undergoes energy release and dissipation. Moreover, the particle size has an important effect on the energy evolution of the crushed waste rock. Waste rock with various particle sizes corresponds to different compaction effects and energy release and dissipation phenomena. Therefore, studying the energy evolution of crushed waste rock under compaction is of great significance for revealing the control mechanism of dynamic hazards induced by hard roofs. …