Instability Mechanism of a Multi-Layer Gangue Roof and Determination of Support Resistance Under Inclination and Gravity
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Instability Mechanism of a Multi-Layer Gangue Roof and Determination of Support Resistance Under Inclination and Gravity Panshi Xie 1,2 & Yingyi Zhang 1,2
&
Shenghu Luo 1,3 & Jianjie Duan 1,2
Received: 7 April 2020 / Accepted: 18 June 2020 # Society for Mining, Metallurgy & Exploration Inc. 2020
Abstract A multi-layer gangue roof of a steeply dipping coal seam with a large mining height face area was analyzed using physical simulation, numerical simulation, theoretical analysis, and field measurement methods to evaluate the roof deformation and the mechanisms associated with the instability of the hard gangue and soft coal interlayer. The results indicated that the first weighting step of the multi-gangue roof was larger than that of a non-gangue roof, but periodic weighting steps were similar. The overburden collapse height was lower in the multi-gangue roof than in the non-gangue roof due to the buffering and supporting function of the collapsed gangue. Moreover, the failure of the coal interlayer was the key factor in the collapse of the multi-layer gangue. A mechanical model was established for the hard gangue and soft coal interlayer based on a revised Prandtl squeezing theory. The limited load of the interlayer and maximum resistance of the shield support was thus modeled. The maximum resistance of the support increased with the dip angle of the seam and burial depth. It also increased with the interlayer thickness at thicknesses below 2.75 m. It reached a peak when the interlayer thickness was between 2.75 and 3 m and exhibited a decreasing trend when the thickness was greater than 3 m. The results were confirmed using physical simulation and a field test. Certain measures were proposed to control the stability of the gangue roof, including zoning control of the mining height and resistance and advancing the support while maintaining roof contact, thus ensuring the integrity of the support and surrounding rock system. Keywords Steeply dipping coal seam . Hard gangue and interlayer with soft coal . Limit load . Stability control
1 Introduction Steeply dipping coal seams (with inclination angles between 35 and 55°) [1] account for approximately 15–20% of the coal reserves in China. More than 50% of such deep coal seams are made up of high-quality coking coal and anthracite. Fully mechanized caving mining with large mining height is an effective method for mining steeply dipping thick coal seams
* Yingyi Zhang [email protected] 1
School of Energy Engineering, Xi’an University of Science and Technology, Xi’an 710054, Shanxi, China
2
Key Laboratory of Western Mine Exploitation and Hazard Prevention Ministry of Education, Xi’an University of Science and Technology, Xi’an 710054, China
3
School of Energy Mechanics, Xi’an University of Science and Technology, Xi’an 710054, Shanxi, China
[2, 3]. The most important safety aspect associated with this type of mining is the stability and control of the roof [4, 5]. When soft coal and hard gangue make up the immediate roof of a working face, the soft coal inte
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