New Technology for Longwall Ground Control. Proceedings: U.S. Bureau of Mines Technology Transfer Seminar. Pittsburgh, PA: U.S. Bureau of Mines, 1994 Aug; :37-51
MULSIM/NL, developed by the U.S. Bureau of Mines (USBM), is a three-dimensional boundary-element-method computer program for stress analysis of coal mines. The PC-based program computes stresses throughout a mine. Engineers can then judge whether the stress levels are acceptable and, if not, adjust the mine layout accordingly. Users need material properties for coal, gob, and surrounding rock mass. In this paper, tables give suggested values for Young's modulus of the rock mass and suggested input parameters for strain-hardening gob, and figures give suggested input parameters for strain-softening coal. Different approaches are discussed for assigning material prperties in MULSIM/NL models, namely: (1) uniform, (2) confinement, (3) width-to-height (w/h) ratio, and (4) combined. An example analysis of a longwall panel shows how to select and assign material properties to a model based on these suggestions. Discussions illustrate how to interpret the stress analysis results. A second example shows the analysis of a longwall panel that lies under oald workings. The advantage of MULSIM/NL is that it can analyze complicated mine layouts, including multiple-seam interactions. The stress information provided by MULSIM/NL can help coal mining engineers avoid hazardous ground conditions, expensive repairs, and costly production delays due to inadequate mine planning.