Movement Law Of Overlying Strata In Ascending Mining Method And Relevant Position Optimization On Gateway

Movement Law of overlying strata and layout of the overlying mining gateway in 13-1 coal seam were studied after the first workface of 11-2 coal seam mined out in East Zhuji coal mine. The strata subsidence was simplified as deflection of a thin plate which was simply supported on four sides in order to describe it by mathematical method. Probability integral method which is often disappeared in predicting the ground surface subsidence was used to analysis the internal displacement of overlying strata after protective layer mined out. Similar simulation experiment was also carried out in the laboratory to research on movement law of overlying strata and mining disturbance on 13-1 coal seam, instability index was put forward based on FLAC3 D numerical experiment to analysis the position optimization on mining gateway of 1111(3) workface. Results obtained in this paper were shown as follows:(1) The strata subsidence was simplified as deflection of a thin plate which was simply supported on four sides in order to describe it by mathematical method, in which a formula and boundary conditions of single gently inclined strata were put forward. Probability integral method which is often disappeared in predicting the ground surface subsidence was used to analysis the internal displacement of overlying strata.(2) Similar simulation experiment was carried out in the laboratory to research on movement law of overlying strata and mining disturbance on 13-1 coal seam. Main roof would break periodically after immediate roof broke and the roof weighting step was nearly 20-30 m with the advance of workface. 13-1 coal seam sank concordantly with the maximum horizontal and vertical displacement were-130.5mm, 99.8mm and 1.55 m as it located at the bending zone of 11-2 coal seam. The coal seam would also suffer a breakage of volume with the expansion and compression of 15.79 mm and 19.07 mm. The small deformation of 13-1coal seam shown that though the entirety suffered a certain degree of damage, it could maintain continuity which satisfied the basic bargain ascending mining method.(3) Finite element numerical calculation software FLAC3 D was used to analysis the influence of interlayer distance and alternate distance on the stability of gateway. The concept and calculation formula of instability index was put forward based on result of numerical calculation. We optimized the layout of overlying mining gateway though analyzing the instability index of different zone and the best position is ensured to left a internal displacement of 15m-20 m to the mining gateway of 1111(1) face in 11-2 coal seam.(4) The mining gateway of 1111(3) face in 13-1 coal seam was excavated as designed to left a internal displacement of 15 m to the mining gateway of 1111(1) face in 11-2 coal seam where the stress environment was relative good and the structure could keep complete. Bolt support parameters during the driving period was decided based on the results of numerical calculation experiment, it efficiently kept gateway stable for having a cumulative deformation of 114 mm between roof and floor, besides that the gateway working slopes also had a small deformation of 40 mm. Small deformation of the gateway surround rock shown that the bolt support program could keep the gateway away from suffering huge deformation in the driving period.