Design and Development of An Innovative Coal Utilization Byproducts- Based Crib Element for Underground Mine Support

摘要

Underground mines extensively use prismatic timber elements (typically 5-6 in. squareand 30-36 in. long) to construct cribs for support of roof and floor. Such cribs can carryabout 70-100 ton load. The overall stiffness of the crib is low ranging from 30,000 to60,000 psi depending upon the quality of timber used. Furthermore, the quality of timberis highly variable resulting in highly variable support characteristics. Such cribs alsoprovide considerable resistance to airflow. Deforestation, for utilization of timber as roofsupports in mines, should become more difficult in the future, as global warming issuesbecome important.The principal author designed and demonstrated first generation CUBs-based cribelement, similar to a wooden crib element, about six (6) years ago. The author has nowdesigned and developed second-generation coal utilization by-products (CUBs) -basedcrib element that overcomes most of the disadvantages of a timber and first generationCUBs-based crib element. The developed structural element utilize large percentage(40%) of high LOI (12-18%) coal utilization by-products, have about 2-3 times thestiffness of a timber element, and have post-failure characteristics similar to that of awooden crib element. The elements weigh similar to wooden elements but the designoffers significantly lower airflow resistance. Overall, the developed structural elementshows equal or better engineering characteristics than a timber element and has thepotential to replace timber cribs in underground mines. The developed element isfabricated in a pilot scale facility designed for processing 25-tons per day of CUBs.A review of laboratory data on 2-4 ft high cribs (using second generation crib element)by regulatory agencies led to permission to perform field demonstration studies on alongwall face. CUBs-based cribs were installed in the head gate entries about 200 feetahead of a longwall face. Their performance was compared with wooden cribs installedin the same area. The cribs performed well and compared favorably with wooden cribs.Additional field demonstration tests are planned over the next several months.