Logical design of yield pillar base in longwall mining

Abstract

Longwall is one of the most widely used methods in mining horizontal and gently dipping coal seams. It is a high production method that requires high initial capital investment. Such characteristics enhance the importance of initial design and hence design process. The entries on both sides of the face are integral parts of the method whose accurate design adds to increased profitability and safety of the mining operation. In this paper, two strain-softening models based on analytical fundamentals have been adopted. These models have been applied to a series of yield chain pillars in a coal seam with the depth of 700 meters. Results obtained from this analysis show that such models can be used in deep coal mining and they produce optimum design dimensions and hence they could be adopted as a valid base for logical design of chain pillars. Finally, sensitivity analysis of the results shows that the final design is highly sensitive to the pillar behavior after the coal peak strength. This further demonstrates the validity of the method as a useful tool in designing pillars in longwall deep coal mining.