Study On Stress Distribution And Deformation Characteristics Of Roadside Backfilling Body For Gob-side Entry Of Fully-mechanized Caving And Optimization Of Roof Pre-split Blasting Angle

The vertical deformation at the top and the horizontal deformation near the gob-side entry of the roadside backfilling body is serious in 3307 fully mechanized caving face in Tang'an Coal Mine.This paper is to further study the stress distribution and deformation characteristics of the roadside backfilling body of the gob-side entry with the panel advancement and optimize the roof pre-split blasting angle based on the application situation.The aim is to reduce the stress and deformation of the roadside backfilling body,improve the bearing performance of the roadside backfilling body,and avoid the failure of the gob-side entry retainedTherefore,the research contents are analyzed by means of field investigation,theoretical analysis and numerical simulation.The required support resistance for the roadside backfilling body of the gob side entry is calculated.The distribution of the stress and characteristics of the deformation of the roadside backfilling body are analyzed under the mining influence.Thestress environment of the gob-side entry,the distribution of the vertical stress and characteristics of the vertical deformation of the roadside backfilling body with different pre-split angles are discussed.And the main conclusions are as follows:Firstly,according to the theory of key stratum and the basic law of broken roof strata in gob-side entry,the supporting resistance of the roadside backfilling body is calculated by using superimposed continuous slab model,whose value is11.23 MPa.and also combining with the geological conditions of 3307 fully mechanized longwall panel.Secondly,by means of numerical simulation,the stress distribution and deformation characteristics of the roadside backfilling body in the process of propulsion of the panel are studied.The stress(including the vertical stress,horizontal stress and shear stress)and the deformation(including the vertical and horizontal deformation)show the law that both first increasing and then maintaining stability with the continuous advancement of the panel.The distribution of the vertical stress,horizontal stress and shear stress on the roadside backfiling body show a trend of increasing first and then decreasing on the roadside backfilling body.The vertical deformation shows a non-uniform deformation characteristics with small vertical deformation near the gob-side entry and large vertical deformation near the gob.The horizontal deformation presents a non-uniform deformation feature in the roadside backfilling body with severe deformation of the upper part and moderate deformation of thelower part.Thirdly,by means of numerical simulation,the stress distribution and deformation characteristics of the roadside backfilling body in the mining influence of the adjacent panel are studied.With the advancement of the panel,the vertical stress and the vertical deformation of the roadside backfilling body at different positions under the mining influence are also increasing.Under the first mining influence,the vertical stress of the backfill is symmetrically distributed when the panel is 5m ahead and it shows an asymmetric distribution when the panel is at other distance.The vertical deformation of the top of the roadside backfilling body shows a uniform sinking feature under the first mining influence.Under the second mining influence,the vertical stress of the roadside backfilling body is asymmetrically distributed,and the vertical deformation of the top shows a non-uniform deformation.Meanwhile it is shown that the primary mining has a great influence on the roadside backfilling body in the middle and end of the panel and the second mining has a great influence on the roadside backfilling body in the middle of the gob-side roadway through the analysis and comparison of vertical stress(peak vertical stress)and vertical deformation of the roadside backfilling body beside the roadway in different positions.Finally,by means of numerical simulation,the influence of the angle of the roof pre-split blasting on surrounding rock stress environment of gob-side entry is studied,which is more beneficial to the maintenance of the gob-side entry.It isconcluded that with the increase of the angle of the roof pre-split blasting,the stress environment of surrounding rock of gob-side entry is obviously improved.The vertical stress on the coal wall of the gob-side entry and the roadside backfilling body are reduced from 23.47 MPa and 12.19 MPa to 18.06 MPa and9.55 MPa,respectively.The stress concentration factor in the coal wall side also decreased from 2.76 to 2.12.The vertical stress of the roadside backfilling body shows an asymmetrical distribution characterized by increasing first and then decreasing from the side of the entry to the side of the gob.The peak vertical stress is located at 1.2 m(at the roadside backfilling body near the gob).Meanwhile,the vertical deformation of the backfill is also decreasing,and shows the characteristics of uniform sinking.The optimal roof pre-split angle is 90°.