Coal burst is a high safety and production risk in underground coal mines. It involves a sudden release of strain energy stored within the coal or rock mass due to the disturbance of an unstable state of equilibrium. To improve our understanding of coal burst, it is important to quantify the energy transition involved in this dynamic failure process, since energy sources that cause coal burst are highly complex. This paper provides an overview of progress on understanding coal burst mechanisms, particularly in evaluating two of the energy components associated with coal burst, strain energy and gas expansion energy, using analytical and numerical modelling. Energy release, particularly research on cleating and jointing, is also assessed for a clear understanding of the energy transition process. The energy requirements of the ground support system for coal burst control are then discussed. The paper reports our progress on a multi-element coal burst research in Australia mostly funded by ACARP.
Coal burst is a form of violent and dynamic failure of coal or rock, with high velocity ejection of materials from an abutment or longwall face in underground mines, and is a significant threat to mining safety and productivity. The occurrence of a coal burst is a highly complex process as a range of mining and geological factors are involved that are challenging to quantify. Extensive studies have been conducted to assess the contributing factors, the causal mechanisms and the control of coal burst (Dou and He. 2001; Holland, 1955; Peng, 2008; Zhang et al., 2017 Zhao et al., 2010). Although this dynamic rock or coal failure has been investigated previously from different perspectives, understanding the circumstances in which coal bursts occur and the likelihood of their occurrence in coal mines still needs improvement.
A key element limiting the understanding of coal burst mechanisms is the uncertainty in assessing and quantifying the energy sources, accumulation and release. There are a range of energy components involved and they have different roles and contributions. Recent research in Australia into understanding coal burst (Canbulat et al., 2018) highlighted the following four main research topics:
1. Coal burst mechanisms (both direct and indirect)
a. Energy sources
b. Energy storage (geological units and material properties)
c. Energy release and damage mechanisms
2. Triggers (or causative factors)
a. What causes or initiates failure?
b. How is the energy release manifested?
b. Identification of "coal burst risk domains" at a mine site
a. Preventative measures for elimination of risk (i.e., mine design criteria)
b. Mitigation of risk (i.e., support design)