Collapse behavior and control of hard roofs in steeply inclined coal seams
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ORIGINAL PAPER
Collapse behavior and control of hard roofs in steeply inclined coal seams Dongxu Chen 1 & Chuang Sun 1
&
Laigui Wang 1
Received: 21 April 2020 / Accepted: 13 October 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract The control of hard roof collapse in steeply inclined coal seams is a difficult problem in coal mine operations. We used the Linsheng coal mine as the engineering background and investigated the collapse behavior of hard roofs in horizontal and steeply inclined coal seams using discrete element numerical methods. We designed a pre-splitting blasting scheme of hard roofs in steeply inclined coal seams according to collapse characteristics and performed numerical simulations using discrete element methods. The scheme was applied in the Linsheng coal mine and achieved good results. The hard roof rocks clearly exhibit elastic-brittle plastic failure characteristics; we therefore applied an elastic-brittle plastic strain softening constitutive model to calculate the failure process of the coal strata contact surface, which reasonably reflects the failure characteristics of steeply inclined coal strata roofs. We determined the relationship between the coal seam dip angle and roof collapse degree using discrete element methods to obtain the roof collapse law of horizontal and steeply inclined coal seams. We propose a numerical calculation method of advanced deep-hole pre-split roof blasting using discrete element methods. The obtained numerical results are consistent with field applications, which verify the feasibility of the proposed method in studying hard roof control. Keywords Mining engineering . Steeply inclined coal seam . Discrete element method . Hard roof . Pre-split blasting
Introduction About 15–20% of the total coal reserves in China are located in steeply inclined coal seams (Tu et al. 2014) in which hard rock roofs in the overlying rocks are common (Wang et al. 2009). Under these complex geological conditions, coal mining can easily create a large overhanging roof area in rear goaf, which poses safety hazards such as air leakage and gas accumulation. A roof will collapse upon reaching its loading threshold value; numerous adverse events such as strong airflow, large air pressure changes, rock bursts, and other working face dynamic disasters can introduce serious safety threats to mechanical equipment and personnel (Yang et al. 2014a). The collapse control of hard roofs in steeply inclined coal seams has therefore become an important problem in coal mine production.
* Chuang Sun [email protected] 1
College of Civil Engineering, Liaoning Technical University, Fuxin 123000, China
Previous studies have proposed theories and techniques for studying the control of hard rock roofs and the mining of steeply inclined coal seams. Lv et al. (2019) analyzed roof movement laws under different dip angles, mining depths, working face lengths, and backfill ratio and established a theoretical knowledge base for efficient and safe mining of steeply inclined coa
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