Experimental Study on the Residual Strength of Coal Under Low Confinement

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• 作者：Fuqiang Gao ; Hongpu Kang
• 关键词：Confined compressive strength ; Residual strength ; Failure mechanism ; Coal
• 刊名：Rock Mechanics and Rock Engineering
• 出版年：2017
• 出版时间：February 2017
• 年：2017
• 卷：50
• 期：2
• 页码：285-296
• 全文大小：
• 刊物类别：Earth and Environmental Science
• 刊物主题：Geophysics/Geodesy; Civil Engineering;
• 出版者：Springer Vienna
• ISSN：1434-453X
• 卷排序：50

文摘

In underground coal mining, coal rib failure of longwall entries is almost certain due to the relative weakness of coal and the presence of high mining-induced stresses. To maintain the coal’s capability of sustaining large loads after failure and substantial deformation, it is crucial to understand its post-peak behavior and subsequently, its residual strength. In this study, triaxial compression tests were performed on a total of 51 coal specimens that were classified into two groups based on the existence of calcite grains. Particular emphasis was given to evaluating the residual strength of the coal specimens. It was found that the presence of calcite grains has significant effect on the brittleness of the coal. Coal specimens containing calcite grains have lower frictional strength than specimens without calcite grains. The tests demonstrated that splitting is completely suppressed when the confinement exceeds 10 % of the coal’s unconfined compressive strength. The Coulomb and Hoek–Brown failure criteria satisfactorily fit the coals’ the peak strength data over the entire confining stress range. The Hoek–Brown failure criterion satisfactorily fits the residual strength data. The parameter m for residual strength is significantly greater than that of the peak strength for both groups of coal. It was also found that as the confinement increases, the increase in residual strength is greater than the increase in peak strength.