Drawing mechanisms for top coal in longwall top coal caving (LTCC): A review of two decades of literature

Abstract

This review details the state of the art in research on top coal drawing mechanisms in Longwall top coal caving (LTCC) by examining the relevant literature over the last two decades. It starts with an introduction of the brief history and basic procedures of LTCC. The framework of research on the drawing mechanism, basic concepts, and some theoretical models of LTCC are detailed in sect. research framework of top coal drawing mechanism. The authors note that the Top coal drawbody (TCD), Top coal boundary (TCB) and Top coal recovery ratio (TCRR) are key factors in the drawing mechanism. The Body–boundary–ratio (BBR) research system has been the classic framework for research over the last 20 years. The modified Bergmark–Roos model, which considers the effects of the supporting rear canopy, flowing velocity of top coal, and its shape factor, is optimal for characterizing the TCD. A 3D model to describe the TCB that considers the thicknesses of the coal seam and roof strata is reviewed. In sect. physical testing and numerical simulation, the physical tests and numerical simulations in the literature are classified for ease of bibliographical review, and classic conclusions regarding the drawing mechanism of top coal are presented and discussed with elaborate illustrations and descriptions. The deflection of the TCD is noted, and is caused by the shape of the rear canopy. The inclined coal seam always induces a larger TCD, and a deflection in the TCD has also been observed in it. The effects of the drawing sequence and drawing interval on the TCRR are reviewed, where a long drawing interval is found to lead to significant loss of top coal. Its flowing behavior and velocity distribution are also presented. Sect. practical applications of drawing mechanisms for LTCC mines 4 summarizes over 10 cases where the TCRR of LTCC mines improved due to the guidance of the drawing mechanism. The final section provides a summary of the work here and some open questions. Prospective investigations are highlighted to give researchers guidance on promising issues in future research on LTCC.

Mining‐induced failure characteristics and surrounding rock control of gob‐side entry driving adjacent to filling working face in the deep coal mine

“…It is estimated that over 10 billion tons of coal resources are trapped for protecting buildings, railways, and water bodies from damage, which results in a huge waste of resources 16,17 . To satisfy the need for sustainable development and to avoid surface subsidence, it is imperative to adopt effective technology to maximize the exploitation of these trapped coal resources.…”

“…It is estimated that over 10 billion tons of coal resources are trapped for protecting buildings, railways, and water bodies from damage, which results in a huge waste of resources. 16,17 To satisfy the need for sustainable development and to avoid surface subsidence, it is imperative to adopt effective technology to maximize the exploitation of these trapped coal resources. In recent years, with its unique advantages, a variety of backfill mining technologies has gradually been developed for backfill mining, including solids, pastes, and high-water materials.…”

Creep Fracture Characteristics and the Constitutive Model of Salt Rock under a Coupled Thermo-Mechanical Environment

“…Among the power storage technologies, compressed air energy storage can meet the requirements of high e ciency, large capacity, and long service life at the grid level, so it is valued by countries around the world [7][8][9][10]. Salt caverns are considered as ideal sites for compressed air energy storage because of their high quality geological conditions such as wide distribution, their variety, and large-scale availability, and excellent physical and mechanical properties such as small permeability, low porosity, and compact structure [11][12][13][14].…”

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“…It is usually called an extrathick coal seam when the thickness of the coal seam exceeds 8 m. However, the Datong mining area has developed to the mining of 15 m extra-thick coal seam at present, and more and more extra-thick coal seam working surfaces are gradually established. [1][2][3][4][5] The technology of longwall comprehensive mechanized top coal caving mining (LCMTCCM) has been generally used in the mining of extra-thick coal seams. The research on related technologies of fully comprehensive caving working faces has become a hot spot in the industry.…”