Research On Overburden Strata Migration For Partial Backfill Longwall Mining In Steep Inclined Coal Seam

The key to safe mining of longwall face in steep inclined coal seam depends on the effective utilization and control about the key field of the surrounding rock and the rock mass structure formed.However,the uncertainty key field and variation rock mass structure about longwall mining face in steep inclined coal seam are the key factors that lead to the dynamic disaster of surrounding rock.Partial backfill mining of structural deformation and disastrous deformation in longwall face are carried out.Through the restraining action of backfill body,the key field of surrounding rock becoming and the rock mass structure stabilize are controlled,which is to explore safe and efficient mining of steep inclined coal seam.It is of great significance to enrich the theory of complex coal seam mining.By the multi-disciplinary complex methods of physical simulation,numerical simulation and theory analysis,overburden strata migration under partial backfill mining in steep inclined coal seam was studied.The studied indicate that:(1)The method of partial backfill longwall mining in steep inclined coal seam is put forward.The layout of the area above the artificial filling working surface is given.The mechanical model of the roof rock beam is established,and the three main factors affecting the filling are determined,which are filling rate,filling ratio,dip angle.It is calculated that the location of the roof breakage was shifted from about 0.66 L at 0.55 L.The deflection,bending moment and rotation angle of the roof plate increase with the increase of the full rate,decrease with the increase of the inclination angle,and increase with the increase of the filling ratio.(2)With the increase of the full rate,the stress,displacement and plastic zone range of the roof are all decreasing,but the decreasing trend is not obvious.When the full rate reaches 100%,the stress arch height of the overlying strata is reduced effectively.With the increase of filling ratio,the influence scope of the filling area is getting larger and larger,and the area affected by the fall is getting smaller and smaller.Under the coupling effect of the filling influence area and the declining influence area,the maximum slump location is not located in the upper area of the work,which local in the vertical upper roof of the boundary of the filling body,and the overburden stress arch asymmetry has eased.When the filling by 1/3 to 1/2 change process,the stress of the overlying arch shell decreases 14.5 meters approximately,and the curve is no longer showing the smooth features,the phenomenon of dramatic changes.With the increase of angle,the displacement distribution characteristic is similar to stress,the arch height decreases,and the damage scope of the roof in the filling area decreases.The damage scope of the roof in the unfilled position increases.As the inclination of the coal seam increases from 35° to 40°,the height of the failure zone of the overburden rock decreases from 44m to 38m.(3)Along the strike,when it is unfilled,the strata where the mining face is affected by mining action is higher and the stress on the roof is fully released.The stress value is relatively large.As the full rate increases,the overburden height of the roof is decrease,the stress value also show a decreasing trend.As the filling rate increases,the support load decreases during periodic weighting,the roof weighting step increases,the abutment pressure decreases of coal wall,and the peak abutment pressure shifts to the deep part.Along the tendency,under the effect of filling body,the structure of the key strata has changed,a key pattern in the central region has formed,and the overburden stress arch asymmetry has eased.The upper peak abutment pressure on the working surface is smaller than the lower,and the upper peak abutment pressure is smaller from the coal wall than the lower.As the filling ratio increases,the roof collapse height decreases,and the peak abutment pressure also decrease in working surface,but the upper portion decreases more than the lower portion.