Research On Structural Stability Of Fully Mechanized Mining Surrounding Rock In Shallow Buried And Close Distance Room And Pillar Goaf

When fully mechanized mining is carried out on shallow buried and close distance room and pillar goaf,the stability of its surrounding rock structure is more complicated than that of a single coal seam stope.It is the result of various factors affecting each other.This has severely restricted the safe and efficient mining of this type of coal seam,and it is urgent to conduct in-depth research on the structural characteristics,motion laws and stability of the surrounding rock during comprehensive mining above the shallow buried and close distance room and pillar goaf.Surrounding rock bearing structure is the key to the control of movement and deformation of stope rock.If only the external bearing structure of the bedrock with strong bearing capacity is studied,and the bearing effect of the internal structure formed by the movement of the bedrock on the overburden is ignored,this will lead to the distortion of the calculation results of the stability of the surrounding rock structure.Therefore,according to this kind of mining conditions,this paper studies its stability by combining theoretical analysis,numerical simulation and engineering measurement.The main research results are as follows:(1)The simulation study shows that the stress balance shell formed in the interlayer strata plays a good supporting effect on the overburden after the room and pillar mining of the lower coal seam,and the structural integrity of the surrounding rock is good,and the stress of the rock mass above the interlayer rock is basically unchanged compared with the original rock stress.In the mining process of upper coal seam,the internal bearing structure caused by the movement of bedrock transfers the stress of surrounding rock to the surrounding area of the stope.At the same time,it not only plays an important role in protecting the stability of the rock stratum in the structure,but also can resist the movement and deformation of the stope rock stratum,which has an important impact on the ground pressure performance of the stope The stability of surrounding rock is good after the mining of upper coal seam.(2)The research on the surrounding rock structure of fully mechanized mining in shallow buried and close distance room and pillar goaf reveals the formation mechanism of the box girder bridge structure when the upper coal seam face is first weighting,and determines the stress shell height and web.The calculation formulas of parameters such as width derive the analytical conditions to be satisfied when the system is in balance.The mechanical model of overburden collapse structure under periodical weighting was established,and the calculation formulas of parameters such as pressure,shear force and collapse block length at both ends of the basic top were determined.(3)The fragmentation of the broken rock blocks in the mined-out area not only reduces the height of the free space in the mined-out area,but also its bulk-like characteristics enhance the static deformation performance of the impacted member and absorb more impact energy,which can reduce the impact stress very well.The practice shows that during the mining process of upper coal seam working face,there is no abnormal ground pressure behavior,the surrounding rock deformation of roadway is small,the damage depth is shallow,the surrounding rock stability is good,and the upward safe mining is feasible.