Laboratory and field validation of a LTCC recovery prediction model using relative size of the top coal blocks
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ORIGINAL PAPER
Laboratory and field validation of a LTCC recovery prediction model using relative size of the top coal blocks Jiachen Wang 1,2 & Weijie Wei 1,2
&
Jinwang Zhang 1,2 & Brijes Mishra 3
Received: 13 December 2019 / Accepted: 12 September 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract The recovery ratio of top coal blocks is the direct reflection of drawing effect in longwall top coal caving (LTCC), and predicting the field recovery rapidly and accurately is one of the leading difficult problems. We analyzed the relationship between the recovery and the relative size of top coal, and proposed a recovery prediction model (RPM) in the laboratory. We determined the measurement method of the top coal blocks size, and developed the field setup for measuring the recovery. In addition, we measured the relative size of top coal and the field recovery at four representative LTCC panels in China. The results show that in the laboratory RPM, with increasing relative size of top coal, the recovery increased first and then decreased. Employing the single-opening sequence caving in the panel, the recovery is the maximum when the value of the relative size of top coal is about 0.14. In the field, as thickness of top coal increased, the size distribution curves of top coal gradually changed from convex to concave, and the relative size of top coal gradually increased from 0.005 to 0.202. When the relative size of top coal is large, the recovery also increased and then decreased. However, the value of the field measured recovery is relatively small. When the relative size of top coal is equal to or greater than 0.079, the corrected field RPM can accurately predict the field recovery, verifying the accuracy of the field prediction model. RPM provides a new approach to estimate the recovery, which can greatly reduce the measurement cost and workload, as well as improve the measurement efficiency of recovery. Keywords Longwall top coal caving . Top coal blocks . Average size . Opening length . Recovery ratio . Prediction model
Introduction Longwall top coal caving (LTCC) is an efficient method for extracting thick and extra-thick coal seams, successfully applying in China (Wang et al. 2014, 2015), Australia (Vakili and Hebblewhite 2010), Turkey (Yasitli and Unver 2005; Unver and Yasitli 2006), India (Kumar et al. 2015, 2016; Khanal et al. 2014), Slovenia (Si et al. 2015a, b), Russia (Klishin et al. 2019), and Vietnam (Le et al. 2018, 2019). Figure 1 shows the schematic diagram of a LTCC panel. The shearer extracts the bottom of the coal seam, and * Weijie Wei [email protected] 1
School of Energy and Mining Engineering, China University of Mining and Technology-Beijing, Beijing 100083, China
2
Coal Industry Engineering Research Center of Top-Coal Caving Mining, Beijing 100083, China
3
Department of Mining Engineering, West Virginia University, Morgantown, WV 26505, USA
then the front armored face conveyor (AFC) transfers the extracted coal to the headgate. However, with the mining
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