Implementing energy release rate calculations into the LaModel program

Abstract

Implementing Energy Release Rate Calculations Into the LaModel Program Morgan M. Sears Mining activity at increasingly greater depths and the tragedy at Crandall Canyon that claimed the lives of nine miners have forced coal bump research to the forefront of mining engineering research. Near the end of the last century, the National Institute for Occupational Safety and Health (NIOSH) and the former U.S. Bureau of Mines investigated the mechanics, conditions, and mitigation of coal bumps. Unfortunately, the exact mechanics of coal bumps is still not fully understood. Following this period, research into coal bumps in the United States has been limited. The Energy Release Rate (ERR) calculation quantifies the dissipation ("release") of the gravitational potential energy of the rock mass as mining progresses. This release of energy can occur passively in the form of heat and sound, or dynamically in the form of coal or rock outbursts. From the initial application of a calculated ERR in the deep hard-rock mines of South Africa, the ERR was found to have a significant correlation with the risk or potential of damaging coal bumps or rock bursts. In the mid 1990s, the ERR was incorporated into the MULSIM/NL displacement-discontinuity computer program and used with limited success. In this research, an ERR calculation is incorporated into the modern LaModel computer program to facilitate an analysis for potential coal bumps. Initially, the ERR calculations in LaModel are verified using a case study of cut sequences originally modeled using the MULSIM/NL computer program. Then, the ERR calculations are applied to a bump-prone mine in Southern Appalachia where a number of different pillar recovery cut sequences were used/analyzed in order to minimize the risk of bumps. Incorporating the ERR calculations into the LaModel program further enhances the most widely used boundary-element model to allow for appropriate bump risk assessment. With this new analysis tool, engineers can adequately perform coal bump risk assessments with an increased margin of confidence. iii Dedication This thesis and its accompanying research are dedicated to the miners and rescuers who lost their lives at the Crandall Canyon mine. Without its mainstream media attention, public outcry, and federal legislation, funding for this project would not have been used for the much needed research in the prediction of coal bumps and rock bursts. I would like to thank everyone who made this project possible. I would especially like to thank Dr. Keith Heasley, my advisor, whose hard work and guidance kept me on track through the countless hours involved in this project. In addition, I wish to acknowledge Dr. Syd Peng and Dr. Yi Luo for being committee members as well as instructors and mentors during both my undergraduate and graduate studies. I would also like to thank Dr. Chris Mark who personally recommended me to be involved with this research. In addition, the ground control groups at the NIOSH Pittsburgh Research Laboratory and Spokane Research Laboratory...

Ground stress in mining (part 2): calibrating and verifying longwall stress models.

“…Figure A1 shows an example of such a law. Details of this constitutive law and its verification are found in Appendix G. • Energy calculations were updated to be in accordance with the equations described by Sears [2009].…”

Theoretical study and application of energy extreme value discrimination method of softening zone for bursting hazard

“…Kidybinski 11 proposed that the elastic strain energy index of coal and rock mass should be considered as the bursting liability index. Singh 12 – 14 and Sears and Heasley 15 proposed a method to judge the bursting liability of coal and rock based on an energy release index and analyzed the relationship between the energy release index and the physical and mechanical properties of coal and rock. Tang et al 16 used the residual energy index, obtained from the difference between the elastic strain energy stored before reaching the peak strength and the energy consumed after reaching the peak strength, to judge the bursting liability of coal and rock.…”

Implementing the Local Mine Stiffness Calculation in LaModel

“…The coal itself is brittle and strong with in-situ strength of 984 psi, based on physical tests. The Darby seam is also known for coal bumps due to the unique combination of geology, high topographic relief, and stiff overburden/interburden characteristics (Newman, 2008;Sears, 2009).…”

“…Multiple seam mining is also practiced in the area and the ability to stack pillars is not typically possible. This situation occurs because different operators who do not wish to divulge proprietary information often conduct mining simultaneously, seams have different mineral owners who wish to maximize their own recovery, or old working may have random pillar layouts with remnant and/or irregularly shaped pillars (Sears, 2009). This means that the contributing mechanisms for coal bumps in the area may be: thick overburden, massive competent formations surrounding the coal seam, and stress concentrations multiple seam mining.…”

“…Currently, three techniques are commonly used to evaluate a dynamic pillar failure event: energy release rate calculation, seismic monitoring and local mine stiffness calculation (Ellenberger and Heasley, 2000;Garvey and Ozbay, 2012;Salamon, 1984;Sears, 2009;Sears and Heasley, 2009;Zipf, 1999). These approaches, combined with the advanced computer technology, provide potential numerical tools for analyzing dynamic failures timely.…”