METHOD AND SYSTEM FOR DETERMINING RATIONAL WIDTH OF GOB-SIDE WORKING FACE UNDER CONDITION OF THICK AND HARD KEY STRATA

Abstract

The present disclosure relates to a method and system for determining a rational width of a gob-side working face under a condition of thick and hard key strata. The method includes: constructing a piecewise function with a width of a gob-side working face as an independent variable; obtaining values of parameters of the gob-side working face; determining a solution set based on the values of the parameters of the gob-side working face, the piecewise function, and a predetermined function threshold; and determining a numerical value according to the solution set as a rational width and mining the gob-side working face according to the rational width.

Description

Claims

1. A method for determining a rational width of a gob-side working face under a condition of thick and hard key strata, comprising: constructing a piecewise function with a width of a gob-side working face as an independent variable, wherein the piecewise function represents a relationship among the width of the gob-side working face and parameters of the gob-side working face, the parameters of the gob-side working face comprising at least a width of a small coal pillar of a gob-side entry, an entry width, a ruptured zone width, a plastic zone width, a uniaxial compressive strength of coal, a buried depth of a coal seam, a fracture angle, an average capacity of overlying rock above a mining area, and a mining area width;obtaining values of the parameters of the gob-side working face;determining a solution set based on the values of the parameters of the gob-side working face, the piecewise function, and a predetermined function threshold; anddetermining a numerical value according to the solution set as a rational width and mining the gob-side working face according to the rational width.

2. The method according to claim 1, wherein the piecewise function is as follows: ud′=d′−a−r−ρnσ1+KP1, whereinwhen a+r<d′<Hcotα ,P1=d′2-a+r22γtanα+d′2−a+r22HΔσtanα ;when Hcotα<d′<2Hcotα,P1=−a+r22γtanα−a+r22HΔσtanα−γH2tanα2−HΔσtanα+γHd′+32Δσd′+Δσtan2α2Hd′−Δσtanα2Hd′2 ; andwhen 2Hcotα<d′ ,P1=3γH+2Δσ2Htanα+γHD−a+r22γtanα−a+r22HΔσtanα ,wherein u(d′) represents the piecewise function, while d′ is the width of the gob-side working face, a is the width of the small coal pillar of the gob-side entry, r is the entry width, ρ is a sum of the ruptured zone width and the plastic zone width, n is a confining pressure coefficient for different areas of surrounding rock, [σ] is the uniaxial compressive strength of coal, K is an incremental coefficient for stope dynamic-load stress of the gob-side working face, P1 is dead load stress of the gob-side working face, H is the buried depth of the coal seam, α is the fracture angle, γ is the average capacity of overlying rock above the mining area, Δσ is a maximum increment of stress transferred from different overlying rock strata above the mining area to the gob-side working face, and D is the mining area width.

3. The method according to claim 1, wherein the determining the solution set based on the values of the parameters of the gob-side working face, the piecewise function, and the predetermined function threshold comprises: inputting the values of the parameters of the gob-side working face into the piecewise function to obtain a function to be solved; andperforming calculation by letting the function to be solved be less than or equal to the predetermined function threshold to obtain the solution set.

4. The method according to claim 1, wherein the mining the gob-side working face according to the rational width comprises: determining an actual width of the gob-side working face based on the rational width, the width of the small coal pillar of the gob-side entry, and the entry width; andmining the gob-side working face according to the actual width.

5. A system for determining a rational width of a gob-side working face under a condition of thick and hard key strata, comprising: a piecewise function constructing module configured to construct a piecewise function with a width of a gob-side working face as an independent variable, wherein the piecewise function represents a relationship among the width of the gob-side working face and parameters of the gob-side working face, the parameters of the gob-side working face comprising at least a width of a small coal pillar of a gob-side entry, an entry width, a ruptured zone width, a plastic zone width, a uniaxial compressive strength of coal, a buried depth of a coal seam, a fracture angle, an average capacity of overlying rock above a mining area, and a mining area width;an obtaining module configured to obtain values of the parameters of the gob-side working face;a solving module configured to determine a solution set based on the values of the parameters of the gob-side working face, the piecewise function, and a predetermined function threshold; anda rational width determining module configured to determine a numerical value according to the solution set as a rational width and mine the gob-side working face according to the rational width.

6. The system according to claim 5, wherein the piecewise function is as follows: ud′=d′−a−r−ρnσ1+KP1, whereinwhen a+r<d′<Hcotα  ,P1=d′2-a+r22γtanα+d′2−a+r22HΔσtanα  ;when Hcotα<d′ <2Hcotα ,P1=−a+r22γtanα−a+r22HΔσtanα−γH2tanα2−HΔσtanα+γHd′+32Δσd′+Δσtan2α2Hd′−Δσtanα2Hd′2 ; andwhen 2Hcotα<d′,P1=3γH+2Δσ2Htanα+γHD−a+r22γtanα−a+r22HΔσtanα,wherein u(d′) represents the piecewise function, while d′ is the width of the gob-side working face, a is the width of the small coal pillar of the gob-side entry, r is the entry width, ρ is a sum of the ruptured zone width and the plastic zone width, n is a confining pressure coefficient for different areas of surrounding rock, [σ] is the uniaxial compressive strength of coal, K is an incremental coefficient for stope dynamic-load stress of the gob-side working face, P1 is dead load stress of the gob-side working face, H is the buried depth of the coal seam, α is the fracture angle, γ is the average capacity of overlying rock above the mining area, Δσ is a maximum increment of stress transferred from different overlying rock strata above the mining area to the gob-side working face, and D is the mining area width.

7. The system according to claim 5, wherein the solving module comprises: a function-to-be-solved determining unit configured to input the values of the parameters of the gob-side working face into the piecewise function to obtain a function to be solved; anda solution set calculating unit configured to perform calculation by letting the function to be solved be less than or equal to the predetermined function threshold to obtain the solution set.

8. The system according to claim 5, wherein the rational width determining module comprises: an actual width determining unit configured to determine an actual width of the gob-side working face based on the rational width, the width of the small coal pillar of the gob-side entry, and the entry width; anda mining unit configured to mine the gob-side working face according to the actual width.