Method for screening key stratum for overburden separation grouting in coal mine

Abstract

A method for screening a key stratum for overburden separation grouting in a coal mine includes: selecting overall analysis objects based on coal mine planning; conducting a primary screening of the analysis objects based on a scope of a subsidence zone; conducting a secondary screening of the analysis objects based on whether there is an old goaf; determining key stratums for screened-in analysis objects, prioritizing the key stratums based on a number of separation spaces and a range of a separation height, setting a safe height based on a diversion fissure zone, and prioritizing numbers of groutable layers based on a potential separation space and a water resistance of a rock stratum; prioritizing the groutable layers based on a fault impact; and comprehensively analyzing grouting priority levels of the key stratums based on results of the three prioritizations, and grouting separation layers of the key stratums in order of priority.

What is claimed is: 
     
         1 . A method for screening a key stratum for overburden separation grouting in a coal mine, comprising:
 selecting overall analysis objects based on coal mine planning;   conducting a primary screening of the analysis objects based on a scope of a subsidence zone;   conducting a secondary screening of the analysis objects based on whether there is an existing goaf;   determining key stratums for screened-in analysis objects based on a key stratum theory; prioritizing the key stratums based on a number of separation spaces and a range of a separation height; setting a safe separation height for key stratums of 50 m based on a diversion fissure zone; and prioritizing numbers of groutable layers based on a potential separation space and a water resistance of a rock stratum;   prioritizing the groutable layers based on a fault impact; and   comprehensively analyzing grouting priority levels of the key stratums based on results of the three prioritizations, and grouting separation layers of the key stratums in order of priority levels,   wherein the key stratums are comprehensively ranked based on the results of the three prioritizations and are given a priority level of superior, medium, or inferior, and the key stratums are grouted in order of their priority level.   
     
     
         2 . The method for screening the key stratum for overburden separation grouting in the coal mine according to  claim 1 , further comprising:
 downgrading or excluding a screened-in separation layer of the key stratum if the screened-in separation layer involves a gas protection layer.   
     
     
         3 . The method for screening the key stratum for overburden separation grouting in the coal mine according to  claim 1 , further comprising:
 selecting a planned-mining working face, rather than a working face under an existing subsidence zone or a mining-completed working face, as the analysis object.   
     
     
         4 . The method for screening the key stratum for overburden separation grouting in the coal mine according to  claim 1 , further comprising:
 excluding an analysis object that is located within the subsidence zone or at a boundary of the subsidence zone, and retaining an analysis object that is located outside the boundary of the subsidence zone.   
     
     
         5 . The method for screening the key stratum for overburden separation grouting in the coal mine according to  claim 1 , further comprising:
 excluding an analysis object with the existing goaf, and retaining an analysis object without the existing goaf.   
     
     
         6 . (canceled) 
     
     
         7 . The method for screening the key stratum for overburden separation grouting in the coal mine according to  claim 1 , wherein prioritizing the key stratums based on the number of separation spaces and the range of the separation height comprises:
 determining a key stratum with more than 5 separation spaces and a total separation height greater than 200 m as a superior key stratum;   determining a key stratum with 3-5 separation spaces and a total separation height of 100-200 m as a medium key stratum;   determining a key stratum with less than 3 separation spaces or a total separation height less than 100 m as an inferior key stratum; and   prioritizing all the key stratums in the order of priority: superior, medium, and inferior, with the order of each key stratum at a same level being random.   
     
     
         8 . The method for screening the key stratum for overburden separation grouting in the coal mine according to  claim 1 , wherein prioritizing the numbers of groutable layers comprises:
 determining a key stratum with more than 5 groutable layers as a superior key stratum;   determining a key stratum with 1-5 groutable layers as a medium key stratum;   determining a key stratum without any groutable layer as an inferior key stratum; and   prioritizing all the key stratums in the order of priority: superior, medium, and inferior, with the order of each key stratum at a same level being random, wherein for an inferior key stratum determined by the prioritization based on the numbers of groutable layers, there are no groutable layers in the inferior key stratum and the analysis object is directly excluded.   
     
     
         9 . The method for screening the key stratum for overburden separation grouting in the coal mine according to  claim 1 , further comprising:
 based on positions of the groutable layers,   determining a key stratum with groutable layers not subjected to a fault as a superior key stratum;   determining a key stratum with at least one groutable layer cut by the fault as a medium key stratum;   determining a key stratum with all groutable layers cut by the fault as an inferior key stratum; and   prioritizing all the key stratums in the order of priority: superior, medium, and inferior, with the order of each key stratum at a same level being random.   
     
     
         10 . The method for screening the key stratum for overburden separation grouting in the coal mine according to  claim 1 , further comprising:
 determining a same level to which a key stratum is assigned in at least two of the three prioritizations as the grouting priority level of the key stratum; determining that the grouting priority level of a key stratum is medium if the results of the three prioritizations on the key stratum are superior, medium, and inferior, respectively; grouting the separation layers of the key stratums in order of grouting priority; and directly excluding a key stratum with inferior groutable layers, without considering the separation layer and the fault impact.