Study On The Reasonable Width And Stability Of Narrow Coal Pillar On The Isolated Island Fully Mechanized Caving Face

In recent years,with the continuous development and improvement of coal mining technology,the implementation of the technique of leaving the narrow pillar in the roadway along the empty road has been widely used in production,and the narrow coal pillar has reduced the loss of the section pillar and improved the coal mining.rate.However,the stability of the surrounding rock of the roadway in the island fully mechanized caving face is relatively poor compared with the surrounding rock of the roadway in the general non-isolate fully mechanized top-coal caving face,and the mine pressure appears more severely.At the same time,the unreasonable width of the narrow pillar of retaining roadway will be unreasonable.The roadway is seriously deformed and damaged,requiring multiple repairs,which not only increases maintenance costs,but also causes hidden dangers to the safety of the working face.In this paper,based on the research background of fully-mechanized fully-mechanized caving face of3204 island in Baisheng Coal Mine,on the basis of summarizing and drawing on the achievements of previous researches,the method of calculating,theoretical analysis,numerical simulation and on-site engineering measurement of the surrounding rock structural mechanics model is used to study the island complex.The surface structure characteristics of the surrounding rock,the distribution law of the bearing stress,the width of the narrow coal pillar retaining the roadway,and the stability of surrounding rock of the roadway along the roadway are presented.The main research results of this paper are as follows:?1?The overburden on the 3204 isolated island fully mechanized face has a symmetrical“T”structure in the vertical direction,and a“articulated triangle block”structure at the top of the working face.Under this structure,the leading support pressure concentration factor and the lateral support pressure concentration factor of the island fully mechanized top-coal caving face are higher than those of the general non-isolized fully-mechanized caving face,and are affected greatly by the mining action.?2?Based on the analysis of surrounding rock structure characteristics of isolated island fully-mechanized caving face,a corresponding structural model of surrounding rock mass was established.Combining the stress differential equilibrium equation,the analytical formula was deduced,and the 3204 fully mechanized caving face was obtained.The marginal limit equilibrium width X₀of the edge of the empty coal body is 1.03m.According to the"inner and outer stress field"theory,the S₀ range of the internal stress field for the fully mechanized face of the 3204 island is 11.6m.From this,it is determined that the theoretical width of the narrow coal pillars along the fully mechanized caving face of 3204 island is 4.12⁷.4m.?3?Numerical simulations were conducted to study the change law of the coal pillar's help and stopage stress field,displacement field and plastic failure zone under the condition of different width coal pillars during the excavation of the roadway and the mining face of the island.With the increase of the width of the narrow pillar of roadway,the internal stress increases,the bearing capacity gradually increases,and the deformation of roadway surrounding rock decreases gradually.From the viewpoint of safe mining of working face,coal recovery rate and economic benefit,the reasonable width of narrow coal pillars along the fully mechanized caving face of 3204 island is 5m.?4?The on-site monitoring data on the surface and deep displacement of roadway surrounding rock and the anchor load show that:When the narrow pillar of the roadway of the 3204 island full mechanized caving face is 5m,the maximum moving distance of the two gangways of the mining roadway is680mm,and the maximum of the roof and floor is The approach volume is396mm,and the roadway support design meets the safety production requirements.