Abstract
Gob-side entry retaining (GER) is a hot issue with regard to saving resources and reducing the drivage ratio in longwall mining. This paper investigates an innovative approach of roof presplitting for gob-side entry retaining (RPGER). RPGER uses the directional cumulative blasting to split the roof in advance. The rock roof within the presplitting range caves in gob after mining. The caved gangue can become the natural rib of the gob-side entry and expands to be the natural supporting body for resisting the upper roof movement. A numerical model of RPGER was established by the discrete element method (DEM), which showed that the supporting effect by the expanded gangue was well functioning. The gob-side entry was in pressure-relief surroundings and featured in the lesser deformation. The roof presplitting design method was presented and validated with a field test. The test illustrated that RPGER reduced the mining pressure on the retained entry side. The expanded gangue on the entry side was gradually compacted. It is the compaction process that played the role of reliving mining pressure, and the compacted gangue became the effective rib of the gob-side entry. The retained entry in the pressure-relief surroundings would stabilize a lagging distance behind the working face. The gob-side entry after stabilization met the entry retaining and the safety production requirements. This work illustrates the mechanism of RPGER and validates its feasibility and efficiency.
Highlights
Coal as a non-renewable energy has been consumed for a variety of purposes regarding industry and livelihood [1]
The maximum pressure decreased by and the average pressure decreased by the help of the caved gangue support, the maximum pressure decreased by 16.8 % and the average. These results showed that the approach changed the fractured roof action mode on pressure decreased by 18.9 %. These results showed that the roof presplitting for gob-side entry retaining (RPGER) approach changed the fractured the roof presplitting
This study investigates an innovative approach of presplitting roof for retaining the gob-side
Summary
Coal as a non-renewable energy has been consumed for a variety of purposes regarding industry and livelihood [1]. He et al (2018) [28] studied the RFGEP application haulage entry of Ningtiaota coalmine He et al (2018) [29] studied the key parameters of RPGER in in a thick-seam fast-extracted mining face and tested industrial effect in the S1201 haulage entry the deep medium-thickness coal seam mining and successfully tested its application in the 21304of Ningtiaota coalmine. He et al (2018) [29] studied the key parameters of RPGER in the deep working face of Chengjiao coalmine.
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