Design Considerations for Multiple-seam Mining With Case Studies of Subsidence and Pillar Load Transfer.
Matetic-RJ; Chekan-CJ; Galek-JA
Coal Min 1987 Dec; 24(12):36-40; 28th US Symp. of Rock Mechanics, :1095-1106
The U.S. Bureau of Mines, as part of a program to improve mine planning and development, is currently investigating interactions associated with multiple-seam mining. Two common interactions that occur between adjacent coalbeds are subsidence and pillar load transfer. This study involves underground observations and measurements at two mines each affected by these interactions. At the mine affected by pillar load transfer, overburden depth reached a maximum of 1,000 ft (303 m) in the problem area, innerburden thickness was less than a pillar width (30 to 35 ft) (9.1 to 10.6 M), and instrumented pillars in the upper mine showed a ratio of piller core pressure to skin pressure of 8:1. At the mine affected by subsidence, measurements showed that undermining had little effect on upper mine pillar stability, but had a more sever effect on the development and maintenance of entries. Roof-to-floor measurements recorded over four times more convergence in entries developed over gob as compared with entries developed over support pillars in the lower mine. Alternative design and ground support considerations are discussed for both case studies.
Coal Min., V. 24, No. 12, Dec. 1987, PP. 36-40; 28th Us Symp. of Rock Mechanics, PP. 1095-1106