Study On Roadway-in Support Along The Gob-side Entry Retaining In No.3 Coal Seam Of Dongfeng Coal Mine

With the promotion and application of the technology of gob-side entry retaining,thecomplex diversity of the surrounding rock conditions in China's coal mines puts forward higher requirements for the roadway supporting technology.This work studied the roadway support of the 3G20 gob-side entries as engineering background of the gob side entries of No.3 coal seam in Dongfeng Coal Mine.Through the methods of theoretical analysis,numerical simulation,similar material simulation and field experimental,we designed the lane supporting scheme which could improve support efficiency and verified it by field experiments.The scheme solves the problem of failure of gob side entries anchor cables in the Dongfeng coal,and provides reference for support design of roadway support in similar geological conditions.(1)The analysis shows that some breaking anchor bolts in the roadway roof of 3620 working face are caused by the abutment pressure of secondary mining and lateral goaf.With the advancing of the working face,the superimposed stress peaks are continuously transferred to the deep part of the real coal,and the shallow surrounding rocks are subjected to the phenomenon of expansion along the roadway due to repeated loads.The amount of separation generated by the roof is greater than the deformation limit of the anchor cable,resulting in the failure of support structure.It is clarified that the eccentric arrangement of the anchor cable has the function of promoting coordination between the concrete wall and the deformation of the solid coal in the stage where the surrounding rock of the roadway is influenced by the secondary mining,and improves the stability of the anchor cable in the asymmetric deformation tunnel.The key to the control of surrounding rock is to improve the carrying capacity of the solid coal and the breaking capacity of the roof on the side of the goaf,and to reduce the impact of the broken rock in the goaf on the key block B.(2)According to the analysis of surrounding rock conditions of roadway in 3620 working face,the 6.5m thick sandstone can be used to design the roadway support.The results of roadway similar simulation experiments show that the roadway sag angle under this geological condition is 55°,and the eccentrically arranged anchor cable has better control capability than the middle cable anchorage.In view of the asymmetrical deformation distribution in the gob side entries,an anchor cable arranged on the side of the goaf can play a betterb role in controlling the top area in the asymmetric deformation roadway.(3)Based on the research results above,we designed the support scheme which is compatible with the 3G20 gob side entries.The reliability of the scheme was verified by numerical simulation and field observation.The new lane way support design can combine with the concrete wall to constrain the direct top turning sinking and effectively reduce the possibility of anchor cable breakage as well as improve the integrity of the surrounding rock structure.In addition,this scheme could ensure the safety and normal production of the working face and provide an effective basis for further research on the support technology for the laneway gob side entries.