Geomechanical properties of rocks are necessary for design and construction of various geotechnical and mining projects. These parameters play significant roles in rockmass classification of coal mine roofs and roof control design. Two of the most important geomechanical parameters for designing of various geotechnical projects such as underground excavations are Unconfined Compressive Strength (UCS) and Indirect Tensile Strength (ITS). However, these test methods are time-consuming, expensive and tedious. Also, due to weathering of specimens, after long periods of time, the testing process either is not possible or the test results do not represent an accurate estimation of the rock parameters. In contrary, the Axial and Diametral Point Load test methods (APL and DPL, respectively), are simpler and quicker tests. The loading and failure mechanism of UCS and ITS tests are similar to APL and DPL, respectively. Also, the geomechanical properties of rocks are highly dependent on their moisture content, which play a vital role in long-term planning of geotechnical and mining projects. In this study, an extensive database containing geomechanical properties of three different rock units, i.e., shale, limestone and claystone is developed by collecting and performing tests on obtained roof core samples from a coal mine in the Illinois Basin. The correlation between UCS index and the axial point load index as well as the relationship between the ITS index and diametral point load index are proposed for design purposes. Also, the effect of moisture content variation on the strength reduction of different rocks is demonstrated. This effect on the prediction of a roof fall incidence is investigated and verified by integrating numerical analyses and underground roof fall observation in the studied coal mine in Illinois Basin. Furthermore, using the calibrated numerical model, the effect of influential factors such as room entry width, roof layers, roof supporting system, rock’s moisture sensitivity, and roof layers discontinuity are analyzed. The stability concerns in an underground construction such as a mine could be detected in advance using the methodology presented in the paper. This will enhance the safety and alleviates financial loss.
|Commitee:||Fries, Ryan, Qi, Yan|
|School:||Southern Illinois University at Edwardsville|
|School Location:||United States -- Illinois|
|Source:||MAI 55/03M(E), Masters Abstracts International|
|Subjects:||Civil engineering, Mining engineering|
|Keywords:||Coal mine roof, Mine stability, Moisture sensitive rocks, Point load test|
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