Abstract
In view of problems with roadways with a compound roof, such as the occurrence of instability in the roof strata, ease of separation of the layer caving, difficulty of maintenance, and poor safety, we established a mechanical calculation model of a roadway with compound roof using the elastic mechanics theory, taking the stability control of a roadway with compound roof at a coal mine in Guizhou Province, China as the research background, and based on the actual characteristics of the coal seam and the roof and floor slate. Expressions of the separation layer and instability limit load of compound roof were derived, and the calculation and verification were carried out in combination with the actual conditions. By means of numerical simulation, the distribution and evolution laws of stress, displacement and plastic zone of roadways with a compound roof were studied, and the deformation characteristics and instability mechanism of roadways with a compound roof were revealed: (1) in early stage deformation of roadway, the amount is large, the speed is fast, and the scale is wide; (2) compound roofs are vulnerable to abscission and instability, the bearing capacity of the two sides is low due to softness and cracking, the shear failure of side angles and vertex angles weakens the strength of surrounding rock, and the self-bearing capacity of surrounding rock is low; (3) the bolt and anchor bear relatively large tensile force, and the support structure is easy to be broken up. On this basis, the stability control principle of a roadway with compound roof tunnel was put forward: fast and timely support; high-strength bolt strong support; improving the stability of the roof and the bearing capacity of the two sides; restraining the shear failure of the key bearing parts such as the side angles and the bottom angles, and targeted stability control technology for roadways with a compound roof was developed. The field industrial test showed that the deformation of this roadway with a compound roof was effectively controlled and the overall stability of the roadway was effectively improved. The results of this study could provide useful reference for a roadway with a compound roof under similar conditions.
Highlights
Among mine accidents in China, roadway roof accidents account for the majority, while among roadway roof accidents, those involving a compound roof are the most severe
The compound of the transportation roadway of mining face 1603 consists of mudstone, The compound roof of the transportation roadway of mining face 1603 consists of mudstone, the the 3#, 4#, and coal seams, and their tonsteins
All kinds of joints and cracks develop in thewhen compound roof, and they haveconvergence a large impact on mm, and the deformation of two sides is mm; it is min later, the roof is 258 the weak link of rock, the weakness of which is enlarged after the roadway is excavated, and rock is the overall strength of rock
Summary
Among mine accidents in China, roadway roof accidents account for the majority, while among roadway roof accidents, those involving a compound roof are the most severe. Wu et al [24–27] put forward the criteria and basis for judging separation stability, through five levels and six orthogonal factors including original rock stress, roadway width, compound roof lithology, compound roof thickness, structural cohesion, and structural internal friction angle that affect the separation of the compound roof. He et al [28–31] analyzed the characteristics of a jointed compound roof, pointed out its deformation mechanics mechanism with dual attributes of expansion type and structural deformation type, studied the transformation process from composite to a single mechanical mechanism, and put forward the form and sequence of combined support with bolt, mesh, and cable. This work is beneficial in furthering the excavation and support process for complex and difficult roadways, which is of important theoretical value and practical significance
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