Abstract
One of the most challenging safety problems is ground instability during crossing overlying remnant pillars (CORP). Ground instability not only causes injury to miners or fatalities, but also leads to interruptions in the mining operations and breakdowns in equipment. In this paper, 12 major parameters influencing the ground instability were firstly determined based on extensive international experience associated with CORP. The consequences of the ground instability were then assessed in terms of miners' health and financial losses. Afterwards, a practical method to assess the ground instability risk of lower-seam longwall panels during CORP was developed based on its probability and consequence. Finally, this method was successfully used to determine the best scheme for CORP of LW10-103 at Mugua coal mine. The main advantage of this method is that it enables mining engineers to easily use international experience for assessing the risk of ground instability and selecting reasonable supports during CORP.
Highlights
As the intensity of coal mining increases, coal resources at shallower depths continue to decrease, so there is a need to extract lower seams in many mining areas [1,2]
The risk assessment confirms that the risk level of ground instability is extreme, as shown in table 8
Various types of difficulties resulting from overlying remnant pillars, including ground instability in the face and entries, pose a significant threat to mining operations, equipment and miners’ health in the lower seam
Summary
As the intensity of coal mining increases, coal resources at shallower depths continue to decrease, so there is a need to extract lower seams in many mining areas [1,2]. The longwall workings will cross the overlying pillars in order to 2 maintain the continuity of production and increase the recovery of coal resources [3]. Crossing overlying remnant pillars (CORP) increases the risk of ground control. The lower-seam longwalls need to cross these remnant pillars for continuing mining. Another situation is that the upper and lower working faces have the same advancing direction. At this time, entries will be staggered from the overlying remnant pillars to ensure the stability of the roadway. The lower-seam longwall will inevitably be affected by the overlying remnant pillars during the extraction
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