Date of Graduation
Several different longwall subsidence prediction techniques were analyzed in this study in order to select the most appropriate method for modification and expansion to various field conditions and general applications. These techniques include those developed by the United States Bureau of Mines(USBM) and the National Coal Board(NCB), in addition to the following influence functions: (1) Bals, (2) Knothe's, and (3) zone area. The method that was selected as most appropriate for modification was initially developed from a recent field study conducted in Northern West Virginia over a three year period at 3 different mine sites. The model was refined and generalized using data from 10 different sites located throughout the United States. The refined model considers the mechanisms of ground movements in the vicinity of the longwall extraction in order to predict the maximum possible subsidence and then utilizes a profile function for predicting the subsidence profile. The model requires basic mine geometry, geology and geomechanical properties of the overburden strata as input parameters. In order to substantiate the relationships hypothesized between empirical equations and input data associated with the subsidence model's geomechanical parameters, several physical models of single longwall panels were tested using sand and gelatin for model material and an optical instrumentation technique (holographic interferometry). Different width/depth ratios, seam heights, and geologic compositions were simulated in two different approaches. The first approach was designed to determine the effect of a stiffer overburden on the extent of surface subsidence (angle of draw). Results indicated that the angle of draw increased with a stiffer simulated overburden. The second approach was designed to investigate the shape of the stress relief zones immediately above the simulated longwall panel. Results from the second approach indicated that "in plane displacements" of the mine models could not be recorded with the optical instrumentation technique available in the Mining Engineering laboratory.
Begley, Richard Douglas, "Development of a mechanistic model for prediction of subsidence over longwall mines." (1990). Graduate Theses, Dissertations, and Problem Reports. 8461.