FEASIBILITY OF LONGWALL MINING IN THE SPURGEON COAL FIELD, PIKE AND WARRICK COUNTIES, INDIANA

CHEN TAIR HUANG, Purdue University

Abstract

The Spurgeon Coal Field, an area of nine square miles, is located in southern Pike and northern Warrick Counties, Indiana. In this region, overburden thickness increases above 120 feet (37 m), and strip mining based on current equipment and highwall procedures is uneconomical. Hence longwall mining, a procedure involving high-productivity and -safety aspects is under consideration. For longwall mining to succeed, several specific geological and mining conditions must occur. An essentially uniform thickness plus continuity of the coal (Indiana Coal V) was determined through examination of drilling data and interpretation of cross sections, isopach maps and structural contour maps prepared. No coal discontinuities (channels, wash outs, faults) were indicated for the Spurgeon Field. Continuous and regular caving of the immediate roof after mining was also necessary for a successful longwall operation. Based on drill core strength, the caveability classification of the immediate roof qualified as "fairly good/good, easy caving". These findings were favorable for adopting the longwall method. An aspect of concern is the shallow overburden (average 150 feet) (46 m) of the field as other longwall mines in the U.S. have overburdens in excess of 800 ft (244 m) and experience is based on these conditions. The general proposed layout and design for longwall mining were evaluated. High horizontal stresses due to the shallow overburden were considered in the design of the chain pillars. Wilson's confining core approach for estimating the location of the peak stress and the tributary area concept of the maximum potential loading were combined to develop a procedure for determining dimensions of the chain pillar. The existence of high horizontal stresses allows for the reduction in size of the chain pillar in the hydrostatic stress state. Owing to the similar geologic condition of the Illinois Basin and the coal fields of England, the SEH (Subsidence Engineering Handbook) approach was used to evaluate the maximum potential subsidence above the central region of the panel. If the panel width selected is above 500 ft (46 m), maximum subsidence should be about 4.1 ft (1.25m). The hyperbolic tangent function was applied to predict the subsidence profile.

Degree

Ph.D.

Subject Area

Civil engineering

COinS