Abstract
This research presents the grouting method of preventing rib sloughage which severely impacts mine safety and longwall retreat speed in thick coal seam with numerical simulation and laboratory tests. Based on the analysis of the plastic failure mode of five types of coal seam, roof strata ahead of the longwall face, and fractures developed in the coal seam, the following results are drawn, the range and degree of plastic failure generated in the coal seam and roof strata ahead of the longwall face gradually decreased as the coal mass strength increased; the grouting boreholes are essentially laid out within the coal rib instead of the roof. For a particular case of a coal mine in Shanxi province, a novel cement-based material was grouted, which fulfilled the reinforcement requirements under the tectonic stress regions and front abutment zones. Besides, the grouting borehole construction requested predrilled boreholes, full borehole intubation, lengthened hole sealing, and multiple-step drilling and grouting. This study can provide a theoretical framework of a design overview and practical basis for similar mining conditions in other coalfields.
Highlights
Thick coal seam resource reserves account for 44% of the total coal supply in China and constitute more than 45% of the total output [1]
Continuous improvement of coal mining technology, coal mining equipment innovation, and ground control theory and technology research related to high-intensity mining all enable an extensive application of the thick seam mining techniques in China
Rib sloughage and roof collapse along the longwall face often occur during the mining process, especially when encountering adverse geological conditions such as faults, collapsed columns, and topple mining zones
Summary
Thick coal seam (thickness ≥ 3:5 m) resource reserves account for 44% of the total coal supply in China and constitute more than 45% of the total output [1]. Rib sloughage and roof collapse along the longwall face often occur during the mining process, especially when encountering adverse geological conditions such as faults, collapsed columns, and topple mining zones. In the minor accident, powered support topples over; in the serious accident, large-area roof caving happens, which seriously decreases advancing speed and may even cause unexpected casualties These adverse effects greatly limit the development of thick seam mining and restrict the mining efficiency of the associated thick seam equipment [3,4,5]. A site test at a thick seam mine was conducted with this new material, and rib sloughage in this longwall face has been successfully prevented, which indicates that the technique of rib sloughage prevention based on geological structure exploration and deep hole grouting in the front abutment zones is applicable and feasible [2,3,4, 6, 8]. This study reports the field results of this new technique
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