Abstract
Alpu lignite field is an important coal deposit with nearly 2 billion tons of coal resources located in the middle of Turkey. The mine deposit consists of three main seams. The thickness of two of them vary from 4 to 30 m. The surrounding rock mass is very poor in terms of strength. The high clay content and weak rock mass make mechanized mining difficult. In this research, applicability of the longwall top coal caving method was investigated. The very weak strength behavior of the coal and the surrounding strata increases the importance of research in the mine site in terms of ground control. The aim is to design the mechanized longwall mine based on ground control principles. First of all, classification of the roof, coal, inter-burden, and floor strata were classified based on geotechnical aspects. Then, cavability index, shield, and floor bearing capacity were investigated. Different methods were applied to understand the limitations of a mechanized system that is very critical due to the very low strength strata. According to the main results, roof strata was classified as immediately caving while mining height was calculated as 5–6 m. Finally, the relations among geotechnical characterizations of roof and floor strata, cutting and caving heights, and required shield capacity were presented based on analytical and numerical applications. The proposed approach can be used as a ground control method for the applicability as well as the limitations of mechanized longwall mining design in weak strata conditions.
Highlights
Longwall mining is one of the most applicable and effective production methods for underground coalmines
The Alpu lignite coal field with its two billion tons of resources was investigated with respect to the design of mechanized longwall mining systems
The mine site consists of three coal seams in various thicknesses called as seam-A, seam-B, and seam-C
Summary
Longwall mining is one of the most applicable and effective production methods for underground coalmines. Mechanized longwall mining requires heavy machinery and equipment that are shearer for coal cutting, hydraulic shields for roof control, and armored face conveyor (AFC) for the haulage of the coal. The low strength behavior in terms of geotechnical properties of floor and roof strata leads to decrease the top coal recovery due to the limit of the longwall working height. The relation between the productivity of coal seam based on geotechnical properties investigated in the study that is the key factor for the recovery of top coal. Strata movement in longwall mining is generally well described and classified in a caved zone that is behave as an immediate roof. The study aims to investigate the applicability of LTCC as a mechanized underground production method. Mechanized longwall mining was investigated for seam-C as an auxiliary purpose of the study
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