Mapping and Application of Roof Joint Patterns for Ground Control in An Illinois Mine

摘要

An analysis of the Roof Falls Data Base (RFDB) forunderground coal mines in Illinois for the period 2004–2008indicated that about 80% of the roof falls occur at intersectionsand are associated with geologic anomalies or a rapidly changinggeologic environment. Most falls are associated with anomaliessuch as clay dikes, differential compaction faults, shear zones,joints and fractures, and geologic structure. Therefore, a betteranalysis of the geology with emphasis on mapping anomalies suchas joints and fractures and their application is necessary to improveground conditions and safety. Such studies within Illinois CoalBasin are limited. This paper presents a mapping study of the jointorientations with documentation of dip of the several lithologicalunits that lie directly above the Herrin No. 6 Coal seam aroundsouthern Illinois. These units include the Energy Shale, AnnaShale, and Brereton Limestone. The mapping was done in threemines and the data were plotted on a stereographic projection todetermine the average characteristics of joint planes. The studymines included two deep underground mines and one shallowhighwall mine. This study has helped identify favorable miningand support orientations in areas of highly variable geology. Theseare currently under review by the cooperating coal company forexperimental roof control studies.