Study On Mining Roadway Supporting Technology Under The Gob Area Of Close Distance Coal Seams

The 1103 working face of the second coal mine in China Coal Pingshuo Group Co..Ltd is the first working face of 11# coal seam. The roadway of 1103 working face is under the gob of 9# coal seam, and there are many negative factors existed. The first is that the average distance between 11# coal seam and 9# coal seam is only 5m, the roof is thin, and the roof of 11# coal seam is destroyed for the mining of 9# coal seam. The second is that the roof is thin and the ordinary vertical cable (the length is 7m) can not be adopted. The third is that the roof is composed of thin fine sand block, mudstone, thin coal shed and so on and it is lithology is bad. The intensity is low and it is broken. The forth is that the coal mine is influenced by the open pit in the East, the South and the North, the horizontal stress in the earth maybe emerges tensile stress, and it is harmful to the stability of roof. The fifth is that the cross section of roadway is big, the width is 5.5m, and the height is 3.5 m.This paper uses the method of theoretical analysis and numerical simulation to study the arrangement and support of roadway in 1103mining face. According to theoretical calculation it is got that the damage depth of the mining of 9#coal seam to the floor is 5.4 m, and the 11# coal seam and 9# coal seam are both close distance coal seam. The 9#coal seam protection coal pillars are stable by analyzed, and the roadway arrangement of the 11#coal seam select internal way. The internal offset distance of the mining roadway of 1103ming face of 11#coal seam is more than 18.5 m by calculated. Take pressure monitoring to the holders of 9#coal seam, infer the destruction that holders to the floor is small in the scale that the distance to the protection coal pillar is 30 m, and at last determine the internal offset distance of the mining roadway of 1103ming face is 24 m. The roadway adopts cable and truss cable combined supporting scheme according to theoretical analysis. According to FLAC numerical simulation calculation, compare the roadway supporting effect of truss cable with different parameters (cable angle, cable length and the distance between porthole and two sides in the truss cable supporting system and number of the roof cable), and it optimizes support parameters. And the optimal supporting parameters are that the angle of cable in the truss cable is 60°, the length of truss cable is 5 m, the distance between porthole and two sides is 0.2 m, and the number the roof cable is 6. The support scheme is applied to the scene. According to the observation of surface displacement and the amount of roof abscission layer, they are got that roof-to-floor convergence is less than 30 mm, roadway sides convergence is less than 100 mm, amount of roof abscission layer is less than 10 mm. The deformation of roadway surrounding rock is small, and the support effect is good.