Year

2016

Degree Name

Master of Philosophy

Department

School of Civil, Mining and Environmental Engineering

Abstract

An outburst of coal and gas is a key safety risk in coal mining and a worldwide phenomenon. It could be described as sudden ejection of gas and coal from a coal face. In multiple-seam mining, a seam with less outburst proneness is often extracted first prior to extract overlying or underlying seams with high outburst risks in order to mitigate the risks. A large number of engineering practices show that this protective mining sequence, aided by pressure relief gas drainage, is quite effective. Gas pressure in coal seams is often measured and used to assess the de-gassing effect and define outburst-free zones in a degassed seam, often practiced in Chinese coal mines. However, this method has its shortfalls. Firstly, site measurement of seam gas pressure is quite time-consuming as it normally takes a few weeks to complete. Secondly, it can also be problematic due to damages to measurement boreholes and their sealing, resulting in inaccurate pressure readings. To address these issues associated with seam gas pressure measurements, gas content in coal was tried to replace gas pressure to define outburst-free zones in a degassed seam.

The field trial was successfully implemented at the 1492 (1) panel mining #11-2 coal seam in Pansan Mine, Huainan, China. The trial results showed that the gas content of the overlying #13-1 seam was reduced from 8.4 m3/t to about 2 - 4 m3/t following mining the #11-2 seam, this was well below the outburst threshold value of 6 m3/t set for the 13-1 seam . The outburst risk of mining the #13-1 seam in the area directly above the 1492(1) panel was completely eliminated. The gas content measurements were carried out using the direct desorption method as described in the Australian Standard AS3980-1999. The results also indicated that the de-outburst zone extended 12 m outside the panel return gateroad and 24 m outside the panel start line. It should be mentioned that the extent of the de-outburst zone is somewhat different from conventional understanding in China that the zone lies about 19 m inside the panel return gateroad and 30 m inside the panel start line under the panel condition while the others are 12 m outside the panel return and 24m inside the panel start line. As the extent of the de-outburst zone is of fundamental importance in integrated coal production and methane extraction in multi-seam mining environment, more investigations are required to evaluate exact boundaries of de-outburst zones.

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