Among all United States underground coal fields, those in Illinois have the highest rate of roof collapse due to its weak and severely moisture-sensitive roof rock units. Rock mass characterization is the key initial step in designing safe and economical roof control in underground coal mines. In this study, performance based roof rockmass characterization is investigated. The geologic conditions as well as underground mine geographic specifications, roof fall analysis, mining method, utilized supplemental roof control measures, and geotechnical properties of roof rock units were considered to link the roof performance to rockmass characterization. The typical roof rockmass characterization methods such as Rockmass Rating (RMR), Q-values, and Coal Mine Roof Rating (CMRR) were utilized to evaluate the roof conditions and roof support design for a case study located in the Illinois Coal Basin. The results of several mine mappings, laboratory test results, and geotechnical issues and concerns are discussed. The roof support designs are analyzed based on the rockmass characterization and are compared with observed performance.
This study shows that 1) CMRR is a reasonable method for characterizing roof rockmass and designing roof support design; 2) Moisture sensitivity and bedding strengths in the horizontal direction are essential parameters for roof support design under weak roof conditions; and 3) Rockmass characterization methods should be modified for rocks that were excluded in the origination of these methods.
|Commitee:||Fries, Ryan, Zhou, Jianpeng|
|School:||Southern Illinois University at Edwardsville|
|School Location:||United States -- Illinois|
|Source:||MAI 55/02M(E), Masters Abstracts International|
|Subjects:||Geotechnology, Engineering, Civil engineering|
|Keywords:||Cmrr, Illinois coal basin, Rmr, Rockmass characterization, Underground coal fields|
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