ABSTRACT
In the US, prismatic wooden elements are extensively utilized in underground mines to construct cribs as a secondary roof support. Such a crib typically carries about 62.5–89.3 tons load with low stiffness ranging from 207 to 414 MPa depending upon the quality of timber. The highly variable quality of timber results in varying support characteristics. With a rapid depletion of high quality timber resources, cost of wooden cribs has increased rapidly. On the other hand, management of Coal Combustion Byproducts (CCBs) from power plants has become a major issue to maintaining a healthy coal industry. Researchers at SIUC believe that a CCBs-based artificial crib has the potential to replace a wooden crib with better performance and cost competitiveness while managing CCBs in an environmentally sound manner. First-generation CCBs-based crib element, similar to a wooden crib element, was designed and demonstrated by Chugh. He and his research team have now designed and developed the 2nd generation CCBs-based crib element that overcomes most of the disadvantages of the 1 st generation crib element. This paper focuses on the design and analysis of the 2nd generation CCBs-based crib. Following mix development and product characterization, structural performance and design of the crib element was optimized based on finite element analysis (FEA). With laboratory test results on 1.22 m high prototype cribs as the input, several 3-D nonlinear FEA models were developed to simulate the behavior of full size cribs under various loading conditions. Analysis results revealed that the artificial crib performs well and compares favorably with wooden cribs. A review of laboratory data and the simulation results on full-size cribs by regulatory agencies led to permission for performing field demonstration studies at a longwall face, which proved that the developed structural element has the potential to replace timber cribs in underground mines.
