Innovative Coal Utilization Byproducts Crib
Underground mines extensively use prismatic timber elements (typically 5-6 inch square and 30-36 in long) to construct cribs for support of roof and floor. Such cribs can carry about 70-100 ton load. The overall stiffness of the crib is very low ranging from 30,000 to 60,000 psi depending upon the quality of timber used. Furthermore, the quality of timber is highly variable resulting in highly variable support characteristics. Such cribs also provide considerable resistance to air-flow. Deforestation for utilization of timber as roof supports in mines, should become more difficult in the future as suitable timber reserves become more scarce. To help address these concerns, Dr. Y. P. Chugh of the Department of Mining and Mineral Resources Engineering at Southern Illinois University (SIUC) in Carbondale, Illinois has designed and developed coal utilization by-products (CUBs) -based crib element that overcomes most of the disadvantages of the timber crib element.
| The developed structural elements utilize large percentage (40%) of high LOI (12-18%) coal utilization by-products, have about 2-3 the stiffness of a timber element, and have post-failure characteristics similar to that of a wooden crib element. The elements weigh similar to wooden elements but the design offers significantly low air-flow resistance. Overall, the developed structural element shows equal or better engineering characteristics than a timber element and has the potential to replace timber cribs in underground mines. The crib element dimensions are 6.25 in x 6.25 in. x 30 inches and each element weighs about 42 pounds (see figure at right). | |
The crib is designed to carry about 90-100 tons of vertical load. The developed crib element is fabricated in a pilot scale facility for processing 25-tons per day of CUBs in McLeansboro, IL. This facility and research is funded jointly by the Illinois Clean Coal Institute and the National Energy Technology Laboratory of the U.S. Department of Energy. Laboratory tests have been completed and have been reviewed by regulatory agencies. The characteristics are suitable for mine use. Field demonstration of the developed crib element was performed at an underground coal mine (Galatia mine in Illinois) utilizing a longwall mining system. CUBs-based cribs were installed in the headgate entries. A side-by-side comparison was made between wooden and CUBs-based cribs. We installed four, 8-ft high cribs (see figures below). As the longwall face passed the installed cribs, we watched the performance of those cribs and compared them to wooden cribs. Except for one crib that was knocked out due to caving, the others performed as good as wooden cribs. The cribs held the designed load and did not fail in a brittle manner. Other benefits of CUBs-based cribs are given below.
Fire proof
Less resistance to air flow
Easier to handle
Much stiffer than wood so they provide immediate support to the roof.
The full report of this project is available by clicking on the link below:
Development and Demonstration of a Pilot-Scale Facility for Fabrication and Marketing of Lightweight Coal Combustion By-Products-Based Support and Mine Ventilation Blocks for Underground Mines (Large PDF file, 2 MB)
