Occurrence Mechanism of Roof‐Fall Accidents in Large‐Section Coal Seam Roadways and Related Support Design for Bayangaole Coal Mine, China

Abstract

This study focused on large-scale roof-fall accidents occurred in large-section coal seam roadways of Bayangaole Coal Mine, Inner Mongolia, China, and investigated the occurrence mechanism of roof-fall and the related supporting control method in detail. Firstly, the fracture characteristics of the surrounding rocks on the roadway roof were measured using a stratum detector. The results showed that the roadway roof underwent the most severe failure with a maximum deformation of 3.53 m; the bedding separation and fracture zones were distributed at irregular intervals. Accordingly, the entire stratum was separated into several thin sublayers, significantly reducing the stability of roof. In addition, the roof medium grained sandstone of roadway is water-rich strata, and water aggravates the damage of roof. Next, the mechanism of the occurrence of roof-fall accidents in the roadway was elucidated in detail. The following three reasons are mainly attributed to the occurrence of roof-fall accidents: (i) effects of mining-induced stress and tectonic stress, (ii) existence of equipment cavern on the side of roadway, and (iii) unreasonable support parameters. On that basis, a new supporting design is proposed, including a more reasonable arrangement of anchor cables and bolts, bolts with full-length anchorage which are applicable in cracked and water-rich roadway, high-strength anchor cables, and crisscrossed steel bands. Moreover, high pretightening force was applied. Finally, a field test was performed, and the mining-induced roof displacement and stress on anchor cable (bolt) were monitored in the test section. The maximum roof displacements at the two monitoring sections were 143 mm and 204 mm, respectively, far smaller than the roadway’s allowable deformation. Moreover, the stress on roof anchor cables (bolts) was normal, and no anchorage-dragging and tensile failure phenomena were observed. The monitoring data indicated that the new supporting design was remarkable on the control of large-section coal seam roadway roof deformation.

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

“…e composite roof generally comprises rock that is layered by soft or hard rock interbred or containing weak interlayers and has weak plane development characteristics for the stratum structure, many weak interlayers, small strata thickness, and low interlayer cohesion force [5][6][7]. Many scholars have studied and discussed the stability of composite roof structures of coal seams [8][9][10][11][12]. e main factors affecting the stability of the composite roof structure are considered to be the lithology of strata, strata thickness, number of strata, strata location, and interlayer cohesive force.…”

Evaluation of the Mechanical Instability of Mining Roadway Overburden: Research and Applications

“…He et al [27][28][29] used the material point method (MPM) to simulate the large deformation and failure process of deep rocks, and proposed the support idea of large deformation roadway under the influence of mining. Gu et al [30,31] measured the failure characteristics of the surrounding rocks on the mining roadway roof by using a strata detector, and investigated the occurrence mechanism of roof-fall and the related supporting control method in detail. Xie et al [32] used discrete element numerical simulation to analyze the separation characteristics of compound roof in mining roadway, and established the gray algebraic curve model (GAM) to predict the roof fall accidents.…”

Influence Law of Interbedded Strata and Their Collapse on the Mining of Extremely Thick Coal Seam under Goaf

“…Close-distance coal seams refer to coal seams with small coal seam spacing and substantial influence on each other at mining operations [8][9][10][11]. As a result, the upper coal seam mining damages the surrounding rock and then transmits stress to the bottom plate [10][11][12][13]. Yan [14][15][16][17] conducted a preliminary study on the joint mining theory of short-distance thin coal seams; Zhu et al [18] conducted a relevant theoretical investigation with the following assumption: the interlayer and upper degraded rock formation were regarded as a block and a loose body, respectively.…”