Kaifang Li

Date of Graduation

2016

Document Type

Dissertation

Degree Type

PhD

College

Statler College of Engineering and Mineral Resources

Department

Mining Engineering

Committee Chair

Keith A Heasley

Committee Co-Chair

Yi Luo

Committee Member

Brijes Mishra

Committee Member

Aaron Noble

Committee Member

Ihsan Berk Tulu

Abstract

Catastrophic failure of mine structures, such as coal/rock bumps and cascading pillar failures, is a difficult and longstanding ground control issue which has presented serious safety problems in coal, metal and nonmetal mines. Although various approaches for analyzing this issue have been proposed, it is still hard to predict and/or to eliminate these violent pillar failures due to the poor understanding of the exact mechanism. The local mine stiffness criterion had been recognized as a promising approach for analyzing the issue of dynamic underground pillar collapses. This criterion was initially hypothesized and tested with laboratory experimentation, but with the advent of appropriate numerical models, it can be extended to analyze the stability of the field pillar. To successfully use the local mine stiffness criterion, the post-failure pillar stiffness and the local mine stiffness need to be accurately calculated. Previous research has roughly determined the relationship between pillar stiffness and pillar geometry, but those results were primarily based on the analysis of specimens in the laboratory, which may certainly have the different scale and stress conditions than real pillars in the field.;The objective of this thesis is to fully implement the local mine stiffness calculation into LaModel. Also, as an integral part of this implementation, an improved method for generating strain-softening pillar behavior based on extensive field data was developed and updated. The implementation of the local mine stiffness and strain-softening coal properties will be validated with a number of test models, and then the practical utility of using the local mine stiffness criterion will be evaluated with the back-analysis of a couple of actual case histories.

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