Study On Reasonable Width And Control Technology Of Small Coal Pillar Gob-side Entry Driving In Dong Huai Coal Mine

Many coal mine enterprises apply narrow pillar drift in order to save resources and safetyin production. However, Dong Huai Coal Mine still uses wide pillars of35-40m to protectroadway, which has wasted numerous rescources. It is imperative to promote the applicationof narrow pillar drift in this Mine with the view of increasing the mining rate and prolongingthe mine service-life. Based on the project of “study on the key technology of narrow pillarmining in Dong Huai Coal Mine”, this thesis analyzes the feasibility of adopting narrow pillardrift in this Mine through theoretical analysis, numerical simulation, field observation and soforth. Then a reasonable width of narrow pillar is designed and a concrete supporting schemeis put forward. The scheme turns to be effective, and to some extent can guide and providerefernence to solve the problem of narrow pillar drift in this region.According to the characteristics of gob-side entry driving, the immediate roofmechanical model of narrow pillar drift in Dong Huai Coal Mine is established and then it issimplified into cantilever. Analysis indicates when the roadway is arranged aroud speciallocation,it will be least affected by the immediate roof. The formula deduced for the plasticzone of narrow pillar through gob-side entry driving shows the smaller the rotating angle ofthe key rock is, the less pressure the upper roof will impose on the coal pillar and thenarrower the plastic zone will be. Under the limite equilibrium theory, the reasonal width ofnarrow pillars is analyzed.The force and deformation of the chain pillars with different width during the period ofdriving and stoping has been studied by numerical simulation. It is found when the width ofthe pillars is3-5m, within the stress decreasing zone formed in working face goaf of theroadway upper section, the pillars suffer ratively little stress and are easy to maintain. Butwhen the width is designed as3m, the pillars are likely to be crushed and lose carryingcapability during stoping in working face. When the pillars are of medium width10-22m, thedeformation of roadway during stoping will be oversize due to the stress concentration. Andwhen the width is35m, the deformation will be small because of the strong carryingcapability of the pillars, but it will waste plenty of coal. Through analyses, the resonablewidth of narrow pillar should be5m. In addition, how the stability of narrow pillars can beinfluenced by the strength and thickness of immediate roof, mining depth, mining height, coalmass strength, horizontal stress and working face distance is studied in this thesis.Study on the interrelation of the surrounding rock support of gob-side entry and the bestsupporting time indicates the importance of exerting the carrying capability of surroundingrock and seizing the reasonable supporting time. The key parts, especially the frail roof, theroof of the roadway’s sides and base angle, should be strengthened to support. Through analyzing the bolt pretension’s impact on roadway supporting, it is concluded that the boltpretension in Dong Huai Coal Mine should be controlled between40～60KN.Peeping at the rock stratum of the mine, it is confirmed the length of the anchor cable ofthe mine should be7m. The reinforced support scheme by mainly using anchor cables istested in the intake airflow roadway of3I01working face in this mine. Compared with theordinary support scheme by anchor bolt used by the mine, this reinforced support scheme ismore effective to protect the narrow pillar.