How stowing affects strata convergence in a shield working

Abstract

At pit 5-6 of the Prokop'evskugol' Group, during the winning work in the Vnucrennii seam, from cross-cut 13 (level+ 60 m, northern panel of pit 6, south) by the shield system with gravity-flow stowing, measurements were made of strata convergence to determine the effect of moving stowage on convergence of seam rock.Seam Vl Vnutrennii is 2.8-8.0 m thick, with a dip of 85-75". The coal is of medium hardness, with cleavage cracks, and is crushed in the hanging and foot walls. The roof is medium-strength argillite, and has thread-like cracks. The immediate floor is weak siltstone with argillite bands, with total thickness of 0.5 m; the main floor is fissured siltstone of medium strength. The seam has not been affected by over-or underworking.Figure i shows the arrangement of the measurement points. The first datum points in the roof and floorof the seam were located in headings before extraction was begun in the first pillar for a period of 35 days, and then with one pillar in advance.The measurements lasted 396 days, during which three pillars were extracted. Pillar 736 (3rd) was extracted with a 6-month break, caused by absence of stowing material. Figure 2 shows the working face arrangement and the roof convergence pattern.The first pillar (70,/) was extracted in 6,/ days, the second (708) in 43 days; extraction of the upper half of fine third pillar (,/86) took 29 days (up to the lengthy break), and the whole of this pillar 8 months (including the stoppage).Over a period of 35 days (before beginning work 30.5 m from the minus level) convergence of strata in the solid coat in the first pillar ahead of the wirming face was 6 mm; at a distance of 12.5 m it was '7.5 ram. The average convergence rate was 0.17 and 0.21 ram/day, respectively. CZ3C3 V--lrnDm ---nr-nE3n OOOO Z J 32 3r 29 28--27"20~r26 . 7~15 708 <r. I 707~1 11125 26 /