Comprehensive Analysis of Stability of Coal Seam Composite Roof Based on Analytic Hierarchy Process

Abstract

The composite roof structure of coal roadway is complex, and its stability is related to lithology of strata, strata thickness, number of strata, strata location, and interlayer cohesive force. Based on a simplified model of the composite roof structure, simulation test, analytic hierarchy process (AHP), and Matlab, programs are employed to comprehensively analyze the structural stability of roofs. The structural stability of the composite roof is demonstrated to decrease with the lithology of strata, strata thickness, and interlayer cohesive force and increase in number of strata and distance of hard-and-thick strata from the roadway. The decreasing order of influence of these factors on the composite roof structure is as follows: lithology of strata, strata thickness, number of strata, strata location, and interlayer cohesive force. Lithology of strata is the main factor affecting stability. The bending strength decreases with the increase in number of strata, and the influence of strata position on stability decreases from the first layer to the fourth layer. According to the AHP, an expression for the comprehensive influence coefficient (k) for the stability of the composite roof structure is proposed, and the surrounding rocks are divided into three levels using this equation: grade I with 0.7 < k < 1 (stable), grade II with 0.4 < k < 0.7 (slightly stable), and grade III with 0 < k < 0.4 (unstable). A scientific basis to evaluate the stability and control of the composite roof of a complex structure is thus provided.