An approach for design of coal pillars in partial extraction coal mining panels with a consideration of roof-pillar-floor interaction.
Pytel-WM; Chugh-YP; Pula-O
Rock Mechanics: Contributions and Challenges: Proceedings of the 31st U.S. Symposium, June 18-20, 1990, Colorado School of Mines, Golden, Colorado. Hustrulid WA, Johnson GA, ed., Brookfield, VT: A.A. Balkema, 1990 Jan; :101-108
In a partial extraction mine layout in coal seams associated with weak floor strata, pillar strength failure, floor strength failure, and roof failures due to differential settlement of adjacent pillars may be expected. In addition, excessive pillar settlement leading to floor heave and surface settlement could also be causes for concern. The relative importance of these failure modes may vary over the panel geometry. Thus, theoretically the pillar and opening sizes should be varied in different areas of the panel to maximize extraction ratio with optimum structure stability. The current mine design practice does not consider different size pillars and openings in different areas of the panel. This paper presents an approach for design of coal pillars in a panel with a consideration of roof-pillar-floor interaction. The main goal of this analysis is to design mine layouts which would maximize coal recovery in different sections of the panel while maintaining pillar, floor, and roof stability. Overriding consideration may include factors such as equipment size, panel eometry, etc. Currently, design of coal pillars is based on strength analysis of a coal pillar and associated floor strata without a consideration of pillar settlements and roof-pillar-floor interaction. The authors think that a design procedure should consider: 1) bearing capacity of coal pillars (pillar strength), 2) bearing capacity of immediate floor strata, 3) differential settlement of adjacent pillars based on strength of roof strata, 4) absolute pillar settlement based on floor heave in mine openings, 5) surface subsidence characteristics such as strains, tilt, settlement particularly where sensitive surface structures are located, and 6) roof-pillar-floor interaction. Over the past three years, the authors have reviewed existing design techniques for design of coal pillars for weak floor strata conditions and developed new techniques which overcome the deficiencies of the existing techniques, Chugh, Pytel and Pula (1989) and, Pytel and Pula (l989b). More specifically, an approximate analytical model (SIU PANEL.2D) for analyzing roof-pillar-floor interaction in one or more panels, Pytel and Chugh (1989), and a general technique for establishing ultimate bearing capacity of a two-layer foundation with c not equal to phi not equal to 0 have been developed, Chugh, Pytel and Pula (1989). These developments now permit the execution of the proposed improved design approach. A brief description of the design elements and the computer program is presented first and it is followed by two numerical examples illustrating the design approach.
Mining-industry; Coal-mining; Mathematical-models; Computer-models; Analytical-models
OP; Conference/Symposia Proceedings
Rock Mechanics: Contributions and Challenges: Proceedings of the 31st U.S. Symposium, June 18-20, 1990, Colorado School of Mines, Golden, Colorado
Southern Illinois University, Carbondale, Illinois