By: B. P. Hucka
This study is intended to help Utah coal operators plan longwall and room and pillar mining operations. Cleat and joint orientations were performed in 22 active mines located in the Book Cliffs, Wasatch Plateau, Emery, and Coalville coalfields in Utah. Since joints in mine roofs very often outline slabs or blocks which may bell if not properly supported, this study should help to improve the safety of mine workings. Further, the productivity of continuous miner operations can be improved if working faces are oriented parallel to the main cleans.
The frequency of cleat distribution and orientation in the seams was investigated and the results of approximately 4000 field measurements are presented both as rose diagrams and contoured stereographic projections (Schmidt). This report also includes the macroscopic and microscopic (maceral inventory and rank determination) descriptions of coal seams, and addresses the extent of healing of cleat planes, sometimes responsible for changes in cohesion, by calcite or other accessory minerals.
Analytical data suggest that cleats in coal and joints in outcrop rocks are the result of tectonic forces. Cleats and joints are influenced by the presence of faults. Generally, in mines located close to faults, divergence of the two main cleat and joint systems occurs, with the face cleats or main joints oriented roughly parallel to the orientation of the faults. Further, cleats in coal and joints in surface rocks maintain the same pattern in the Book Cliffs, Emery, and Coalville coalfields; as a result, they may serve to predict the cleat orientation in coal seams. This phenomenon is important for mine layout purposes. However, in the tectonically more disturbed Wasatch Plateau coalfield, in some instances the cleat directions in the coal diverge with the joint directions, implying that prediction of the cleat orientations in coal is less reliable.
Pages: 47 p.
Plates: 2 pl.
Location: Carbon, Emery, Sanpete, Sevier, Summit, and Utah Counties
Media Type: Paper Publication