Abstract
Synopsis To solve the support stability control problem for a coal face with large angles along both strike and dip (CLSD), the ’support-surrounding rock’ mechanical model has been developed, which takes into account the impact of the dip angle of the seam on the stability of the support in the strike direction. The mechanical relationships of the critical topple angle and critical slip angle of the support along the strike of the coal face with large dip angle and the support height, support resistance, friction coefficient, and other factors have been derived through the mechanical analysis of support stability in the strike direction of CLSDs in the free state, the operating state, and the special state. The research findings were applied to a fully mechanized CLSD in Xinji Coal Mine. The maximum underhand angle and overhand angle in strike are 42° and 25° respectively, and the maximum dip is 39°. It is calculated that during underhand mining and overhand mining, the critical support resistances for avoiding support toppling are 3723 kN and 1714 kN respectively, and the critical support resistances for avoiding slipping of the support are 7405 kN and 6606 kN respectively. Thus, the selection of type ZZ7600/18/38 hydraulic roof support for the coal face is justified. Measures to prevent sliding of the support and the installation of a limiting stop maintain the support runs in good condition and ensure safe and efficient mining of CLSD.
Highlights
A coal seam with a large dip angle (CLDA) is a seam that dips at 35°–55°
CLSD refers to a coal face having a large underhand angle or large overhand angle in the strike direction, as well as a large dip angle
If the working resistance of the support (7600 kN) and the maximum dip angle of the coal face are entered into Equations [10], [12], [14], and [16], neither the critical topple angle nor the critical slip angle of the support in the operating state are reached at the stage of underhand mining or overhand mining
Summary
A coal seam with a large dip angle (CLDA) is a seam that dips at 35°–55°. CLDAs account for about 15–20% of China’s coal reserves and 5–10% of the output. CLDA mining is challenging due to the difficulty in controlling the stability of the roof, floor, and the coal face equipment, the difficult operating environment for workers, frequent accidents, and low extraction rates. Chinese scholars have focused on the support stability control mechanism in a coal face with large dip angle. Lin et al (2004) analysed anti-topple, anti-slip, and skew stability of hydraulic support for fully mechanized caving mining under the condition of large dip angle based on statics. They studied three kinds of stability of hydraulic support for fully mechanized caving mining with large dip angles. All the research findings to date that analyse the support stability start from the point of view of the coal face dip angle. There are few reports in the literature on research into support stability for CLSD
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