Date of Graduation
Statler College of Engineering and Mineral Resources
Keith A Heasley
LaModel uses a laminated overburden boundary-element model and can not only calculate seam-level stresses and displacements but also surface subsidence for thin tabular deposit such as coal seams. Up to this point, the material property wizards in LaModel were primarily designed for calculating accurate stress redistribution in single and multiple-seam situations and for investigating and optimizing pillar sizes and layouts in relation to overburden, abutment and multiple-seam stresses. However, the critical input parameters which will give the most accurate seam-level stress distribution do not necessarily produce the best surface subsidence prediction. The objective of this research is to develop a methodology for calibrating the critical input parameters in LaModel to produce the most accurate surface subsidence prediction.;For optimum surface subsidence prediction, it was found that the overburden stiffness as defined by the laminations thickness and the gob convergence as defined by the final gob modulus were the two most critical parameters that needed to be calibrated. Using the WVU (Comprehensive and Integrated Subsidence Prediction Model) (CISPM) program as the best empirical subsidence curve, numerous LaModel runs were performed in order to find the values of lamination thickness and final gob modulus which minimized the least-square error between the CISPM and the LaModel subsidence curves. This subsidence matching process was performed for panels with an assumed offset at the edge of the panel (as typically done with empirical subsidence prediction models) and for panels without an assumed offset. Through this curve fitting process, it was determined that the final gob modulus is best determined as a function of the subsidence factor and the lamination thickness is best determined as a function of overburden depth and/or the panel width--to-depth ratio. Ultimately, three different empirical formulas relating the lamination thickness to the overburden depth and/or the panel width-to-depth ratio were determine for the four cases of: subcritical or supercritical panels, with and without offsets. Further, if the user has measured data for subsidence factor and angle-of-draw, the optimum final gob modulus and lamination thickness can be determined from the measured data. These new subsidence prediction formulas have been implemented into new material wizards in LaModel.
Yang, Jian, "Calibrating LaModel for Subsidence" (2016). Graduate Theses, Dissertations, and Problem Reports. 6998.