Study On Mechanism And Parameters Of Gob-side Entry Retaining Under Limestone Roof Condition

Hard roof is common in China with a wide distribution. Limestone is a typical hard roof with the characteristics of high tensile strength, good toughness and difficult to fracture. In the process of face mining, limestone roof is difficult to collapse with many hidden safety dangers. Gob-side entry retaining is an important development direction of coal mining in China with many advantages such as increasing coal recovery ratio, dropping tunnel heading rate and so on.The study background of this paper is the limestone roof to study the mechanism of gob-side entry retaining under this condition. The research purpose of this paper is to provide evidence for determining the parameters of gob-side entry retaining. Under the premise of ensuring successfully implement gob-side entry retaining, reducing the cost and providing reference for another mines at the same conditions.Firstly, based on the limestone roof occurs fracture or not, the roof movement state can be divided occurs fracture to appear periodic roof pressure and doesn’t occur fracture to appear slowly subsided. The law of roof strata activities about this two conditions were studied. Secondly, by using the theories of “Superposition Laminates” and “Elastic Foundation Plate”, this paper established two mechanics model of gob-side entry retaining with limestone roof. It also analyzed the action mechanism between supporting and surrounding rock of gob-side entry retaining under the two conditions. Then, this paper calculated the parameters of supporting. Thirdly, the max deflection of limestone roof when it reach limit span and the free space under the limestone roof was compared to determine the limestone occurs fracture or not. Fourthly, under the background of construction of Xian Dewang Coal Mine 1493 work face with limestone roof, this paper determined the Daqing limestone appears slowly subsided. The economic comparison was also discussed to determine the scheme of gob-side entry retaining, which is the filling body in the roadway and implement roadway excavation at another side. The scheme of roadway support was also optimized. Finally, as the low efficiency of profit, the scheme wasn’t carried out in industrial test. So, it used FLAC3 D to forecast the effect of this scheme and parameters. The results showed that the scheme and parameters were reasonable and feasible, it can be ensure the success of gob-side entry retaining.