ABSTRACT
Multiple seam mining and its associated problems are very serious in Southern West Virginia where poor planning or lack of knowledge in seam interaction often results in complete loss of coal properties. Several measures have been proposed to alleviate the interaction problems under various multiple seam conditions, but few of them are specific in terms of mining plan. Two parallel approaches are adopted for this paper. One is field investigation which consists mainly of mine site visits and gathering of data. The other is the two-dimensional finite element simulation of mine workings using the data gathered as input. Two typical cases which represent the past and present multiple seam mining practice in West Virginia were investigated. Much attention is focused on the interaction problems experienced and the important parameters controlling interaction. Several key parameters controlling interaction in multiple seam mining were analyzed. Proper mining plans, by which the interaction problems can be minimized, are proposed for the individual cases after a better understanding of the interaction mechanism was realized through finite element analyses.
INTRODUCTION
Almost all coal seams in West Virginia are multiple seam, although in some areas it is not so obvious due to non-mining in the adjacent seams or the seam separation is large enough to be ignored. It is, however, becoming increasingly common to mine coal in an area where the working face will be affected by a previously mined-out area or a presently active mine through interaction effects. The adverse ground control problems associated with these interaction effects have increased the risk of mining coal and have attracted more attention (Scurfield, 1970; Whittaker and Hodgkinson, 1971; Dunham and Stace, 1978; Szwilski, 1979; Peng and Chandra, 1980; Stansbury, 1981; Haycocks, et al., 1982; and Pariseau, 1983). During the past decades, the seams selected for mining have been ones of easy accessibility with best physical conditions available and suitability for market desires, i.e. coal with low sulfur and ash, and high heating value. Selection of mining sequence is therefore seldom based on ground control considerations. Problems associated with multiple seam mining are further enhanced by poor planning and the lack of knowledge in seam interaction. As a result, a complete loss of coal properties often occurs. It has been pointed out (Peng and Chandra) that the seam interaction can be avoided, minimized, or on occasion utilized beneficially if careful mining plans are carried out. The development of an optimum mining plan for multiple seam mining should be based on a better understanding of the interaction mechanism, and all possible mining sequences and methods must be considered. Once the optimum mining plans for various multiple seam conditions are developed and made known to the coal operators, it will reduce many unnecessary hardships currently facing multiple-seam coal mining operators thereby greatly reducing the mining cost and increasing coal recovery. Safety and profitability of multiple seam mining will therefore be improved tremendously. This paper presents the results of a recent investigation on two cases of multiple seam extraction and the study of the interaction mechanism.
