Abstract
This paper considers the 333 return airway of the Gaokeng Coal Mine to analyze the deformation characteristics and failure mechanism of the surrounding rock of the composite roof for a loose and weak coal roadway. The reasons for the large deformation are explored and the superiority of the prestressed truss and anchor rope is compared to ordinary anchor cables from the perspective of mechanics to propose a targeted coal roadway support method. Sinking of the composite roof in the coal roadway is accompanied with a release and transfer of the surrounding rock stress. The pressure of the composite roof transfers to the roadway sides and intensifies the fracture process of the coal body. As a result, the ability to support the composite roof is weakened, and it further bends and sinks to form a vicious cycle that repeats itself. Therefore, the support of the composite roof in the coal roadway should consider the roof, roadway sides, and floor as a single unit to achieve the support goal of reinforcing the roadway sides and roof. Based on the above analysis, a comprehensive control technology with a truss and anchor rope is proposed as the main body and a bolt + anchor cable + metal network as the auxiliary. This technology can improve the integral bearing capacity of the composite roof, strengthen the roadway side structures, and reinforce the roadway sides and roof. Numerical simulation and field application results show that the support scheme can effectively realize safe control of the composite roof in coal roadways.
Highlights
With the depletion of coal resources in shallow parts of China, coal mining has gradually extended deeper, the mining environment has become increasingly complex, and the maintenance cost of roadways remains high [1]. e composite roof of a coal mine is composed of rock from different lithologies. ere is a parting face between the rock and its fracture and caving [2, 3]
Liu et al studied the influence of factors, including the lithological characteristics of the roof surrounding rock, roadway section size, rock stress, stratification thickness, and weak intercalation, on the deformation and instability of the composite roof. ey found that the ground stress, size of the Advances in Civil Engineering rectangular roadway section, and thickness of each layer of the composite roof are the three main factors that control its deformation and instability [13]
Chang analyzed the deformation and failure characteristics of the surrounding rock of a mining roadway with a large cross section composite roof in a deep well. ey believed that the roof of each layer is prone to separation due to the high ground stress and dynamic mining pressure, where the deformation of the two sides of the roadway affects the roof stability [14]
Summary
With the depletion of coal resources in shallow parts of China, coal mining has gradually extended deeper, the mining environment has become increasingly complex, and the maintenance cost of roadways remains high [1]. e composite roof of a coal mine is composed of rock from different lithologies. ere is a parting face between the rock and its fracture and caving (weak rock with coal streaks or thin seams produces subsidence displacement) [2, 3]. Chang analyzed the deformation and failure characteristics of the surrounding rock of a mining roadway with a large cross section composite roof in a deep well. Zhao et al studied the failure characteristics of the surrounding rock in deep weak and broken roadways, the composite support method of “shotcreting + grouting anchor bolt + anchor bolt + grouting anchor cable + anchor cable” is proposed by the full-section layer-double arch synergy reinforcement technology [21]. Erefore, this article takes the 333 return airway of the Gaokeng Coal Mine as the research object, analyzes the deformation characteristics of the surrounding rock for the composite roof from a loose and weak coal roadway, describes the reasons for the large deformation, and studies the superiority of the prestressed truss anchor cable compared with the ordinary anchor cable. The comprehensive control technology of the prestressed truss anchor cable is proposed as the main body and the bolt + anchor cable + metal mesh as the auxiliary to ensure the safe use of the 333 return airway in the Gaokeng Coal Mine
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