Controlling And Main Factors Analysis On Roof Of Gob-side Entry Retaining Under Goaf

Depend on gob-side entry retaining of tail entry of11426coal mining face inXieQiao mine, this thesis comprehensive used the methods of theoretical analysis,numerical simulation, and engineering test, analysising the main influence factors andcontrolling technology on roof of gob-side entry retaining under goaf.By using elastic mechanics theory and software MathCAD, analyzed the stressdistribution law of rock stratum under stope; Appling the elastic-plastic theory and slipline field theory to calculate the stope bottom limit yield failure depth of the strata.Using the ground pressure theory, the thesis analyzed formation mechanism andmovement characteristics of the main roof secondary breakage; By using block theoryanalyzed the stability of the "block" of, and expounded the damage process of roofstructure of gob-side entry retaining under goaf.Using FLAC3Dand Tecplot software, numerical value analysised the effects andrespective function of five factors on the stress state and damage depth of rock stratumunder stope, including the floor structure, the mining width, the mining height, thedistance between coal seam and the coal seam dip angle.According to the structure characteristics and damage process of roof, the problemof roof separation and roof falling on the shoulder close to the filling wall should beconsider seriously. Therefore, the support method was put forward, including the U-shape yieldable steel rib, backfilling behind frame, fixing U-shaped rib bolt and anchor,roof reinforcing in pre-filling area, which was applied in the orbital gateway of11426working face in Xieqiao coal mine.The respective function mechanism and theconstruction method was discussed also.The research shows that: the roadway under the goaf is in the stress reducing area,but the roof structure has been widespread damage before mining. In order to ensurethe stability of the roof structure safety, a large number of combined support methodsshould be constructed, of which the supporting intensity is enough to meet theengineering requirements for single coal with the similar conditions. In addition, settingup the U-shape yieldable steel rib increased the construction process, and still need todismantle the fill wall side rib leg when using mechanical templates. Which makes theU-shape yieldable steel rib losing effective supporting capacity, and increasing thepressure of bolts and anchors, even leading to the failure as a whole of the anchor underthe action of shear stress. Therefore, compared with the single coal seam, the gob-sideentry retaining under goaf is more difficult.