Study On Bolt Support Technology Of Coal Roadway Under Goaf In Close Seam

The short distance coal seam group is generally mined by the way of downward mining.After the upper coal face is mined,the roof of the lower coal seam is damaged by the mining stress,and the backward stress of the overlying strata will be transmitted to the bottom coal seam through the section coal pillars,resulting in the complex stress environment of the lower coal seam and the difficulty of supporting the mining roadway.The traditional I-steel shed supporting technology has been used in the mining roadway under the short distance goaf in Chaili Coal Mine,which has the disadvantages of backward technology,poor supporting effect and prone to spontaneous combustion of coal.In this paper,the field test,theoretical analysis and numerical simulation are used to study the bolt support technology in the goaf of Chaili Coal Mine.(1)In view of the problems of backward supporting technology and poor supporting effect in the short distance coal seam in Chaili,the short anchoring and pulling test was carried out on the roof of the mining roadway under the goaf with different layer spacing,and the minimum layer spacing for the anchoring of the mining roadway under the goaf was determined to be 6m.Based on the theory of slip line and the formula of floor failure depth,the floor failure depth of the upper coal face after mining is calculated,and according to the bolt support mechanism,the minimum layer spacing of bolt support is determined to be 5.5m;the minimum layer spacing of bolt support under different layer spacing conditions is determined to be 6m by numerical simulation.According to the analysis results of the above three methods,when the interval is more than 6 m,the bolt support can be used in the roadway under the goaf of Chaili Coal Mine.(2)For the coal seam roadway under the close goaf which can be supported by bolt,the bolt support design is carried out by using the composite beam theory,and the preliminary bolt support parameters of the mining roadway are determined.On this basis,the finite element numerical simulation software is used to calculate and analyze different bolt support parameter schemes,and the reasonable and technically feasible bolt support scheme is determined.(3)The application of bolt support in the transportation roadway of the East 606 working face under the 23 of Chaili Coal Mine shows that the working resistance of two groups of bolts is affected by the driving roadway within 50m from the heading of the roadway,and the working resistance increases.The working resistance between 50-200m from the heading of the roadway is basically stable with little change.Within 200m from the driving head,the roof movement of the transportation roadway is within 140mm,and the total movement of the two sides is within 100mm.It shows that the support system can always maintain the active support for the surrounding rock,the support effect is good,and can meet the requirements of the safety and stability of the roadway.The application of bolt support in the goaf of short distance coal seam is of great significance to improve the technical and economic benefits of the mine,to realize the high-yield,high-efficiency and intelligent mining of the mine,and to the bolt support in the goaf of similar short distance coal seam.