LONG-TERM HIGHWALL STABILITY IN THE NORTHWESTERN POWDER RIVER BASIN, WYOMING AND MONTANA
AuthorSmith, William K
AdvisorGlass, C. E.
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PublisherThe University of Arizona.
RightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
AbstractTime-dependent behavior of natural and excavated slopes in sedimentary rocks is a subject that is poorly understood at present but that is now an important consideration in the design, operation, and reclamation of energy-extraction facilities, in part because of the environmental considerations mandated by the Surface Mining Control and Reclamation Act of 1977 (Public Law 95-87). A slide in an abandoned, unreclaimed strip mine northwest of Sheridan, Wyoming, has been analyzed as an example of a long-term slope failure in the region. This slide occurred in early 1975, some 20 years after cessation of mining. This investigation used Spencer's limiting equilibrium method and an elastic-plastic finite element method incorporating the Drucker-Prager yield criterion. This slide was found to fit the model for time-dependent failure proposed by Nelson and Thompson (1977) in which the time to failure is related to Skempton's residual factor. The Nelson-Thompson hypothesis is extended for use with the three-dimensional Drucker-Prager yield criterion. The residual factor (R) may be computed from the factors of safety with respect to peak (F(p)) and residual (Fᵣ) material properties, using either the Mohr-Coulomb or Drucker-Prager criterion, by the relationship R = [(F(p) - 1)/(F(p)-Fᵣ)] At the present time, the Spencer limiting equilibrium analysis is a more usable tool for ordinary slope design than the elastic-plastic finite element analysis because of the speed, simplicity, and ease of including the effects of ground water in the Spencer analysis.
Degree ProgramGraduate College
Mining and Geological Engineering