Abstract
This study investigates the stability problem of gob-side entry retaining (GER) and backfilling wall which located under the key block B. Based on the combined research of elastic–plastic mechanics, structure mechanics and modern theory of mining-induced pressure, the caving characteristic and roof structure over the GER were analyzed, and the vertical force and the torque on retained entry roof were also derived as the position for the retained entry varies. On the basis of the specific geology in Huainan mining area, the results indicate that a relatively more stable position for retained entry neighbors the hinge point of block A and B, and it also located at a scope ranging from this point to the one-third length of block B in horizontal direction. As to appropriate position for backfilling wall, this study recommends partial-road-in backfilling method for GER. Field trial conducted at panel face 12418 of Xieqiao Mine demonstrates that the recommended width for original entry is 3.6 m and the preferred width proportion between original retained entry and original entry is 75 % or so whereas the avoidable one is 88 % or so. These findings provide qualitative references to the mines which share similar geology as what Huainan mining area characterized.
Highlights
Gob-side entry retaining (GER), which reserves the headgate of previous district sublevel and turn it into the tailgate of district sublevel, is a promising green mining method, and has great economic benefits (Xu 2009; Xue et al 2013; Zhang et al 2014)
This study investigates the stability problem of gob-side entry retaining (GER) and backfilling wall which located under the key block B
Obtained results indicate that deformation law of higher coal side in these five measure sites shows a high degree of consistency, the curves change is obviously not induced by the different size of original entry in Table 2, nor by the specific position of backfilling wall in retained entry in the same table
Summary
Gob-side entry retaining (GER), which reserves the headgate of previous district sublevel and turn it into the tailgate of district sublevel, is a promising green mining method, and has great economic benefits (Xu 2009; Xue et al 2013; Zhang et al 2014). Zhang et al (2005) suggested original-position GER in view of the roof movement law of the fully-mechanized coalface with top-coal caving, whose main technical scheme was to take large section. Huang et al (2011) aimed at the technical difficulties of GER in fully-mechanized coalface with solid material backfilling and they analyzed structural mechanics model of surrounding rock, they put forward a new technical for entry side backfilling. On the basis of the aforementioned results, the vertical force and torque on the gob-side entry were obtained as the position of the entry varies under the key block B, the method of partial-road-in backfilling for GER was presented and applied to the Xieqiao Mine.
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