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dc.contributor.authorChen, Gangen_US
dc.date.accessioned2015-07-28T19:21:19Z
dc.date.available2015-07-28T19:21:19Z
dc.date.issued1989en_US
dc.identifier.urihttp://hdl.handle.net/10919/54779
dc.description.abstractAdopting yield pillars has been considered an effective way of alleviating ground control problems and increasing production. The purpose of this research was to study the behavior of yield pillars and to develop the design criteria. After a literature review, two 2-D finite element models were developed, each following a different non-linear approach. The first model adopted the successive iteration technique incorporated with the Mohr-Coulomb yield criterion. The second followed the elastic—plastic approach, implementing a generalized Von Mises yield criterion. Extensive underground monitoring was conducted and the finite element models were compared with the field data, both yielding promising results. Three different longwall entry layouts were investigated. The yield-stable-yield pillar system was considered to be the best design. A parametric analysis was also performed. The triaxial factor and Poisson's ratio were found to be the most important material properties affecting pillar yielding. The progressive failure hypothesis for pillar design was critically examined. The analysis suggested that the formulation defining the stress distribution in the yield zone under this hypothesis may be satisfied only in extreme cases and, therefore, the actual distribution can be different. An improved equation, describing the stress distribution in the yield zone, was derived by statistically analyzing the results of fmite element simulations. The latter equation fitted the observed field data better than did the original equation, and it was further developed for estimation of yield zone width. Consideration was also given to yield pillar design. Three possible yield pillar sizes were proposed in this paper. The maximum yield pillar size was considered to be twice the width of the yield zone. Based on the pressure arch concept, the minimum yield pillar size was determined by accepting that yield pillars were only supporting the rock strata under this pressure arch. A suggested yield pillar size was obtained by selecting a size which would force the peak stress at the center of the yield pillar to equal the average tributary stress. The case studies conducted in this research indicated that the predicted yield pillar sizes were reasonably accurate.en_US
dc.format.extentxi, 173 leavesen_US
dc.format.mimetypeapplication/pdfen_US
dc.language.isoen_USen_US
dc.publisherVirginia Polytechnic Institute and State Universityen_US
dc.rightsThis Item is protected by copyright and/or related rights. Some uses of this Item may be deemed fair and permitted by law even without permission from the rights holder(s), or the rights holder(s) may have licensed the work for use under certain conditions. For other uses you need to obtain permission from the rights holder(s).en_US
dc.subject.lccLD5655.V856 1989.C536en_US
dc.subject.lcshPillaring (Mining) -- Designen_US
dc.titleInvestigation into yield pillar behavior and design considerationsen_US
dc.typeDissertationen_US
dc.contributor.departmentMining and Minerals Engineeringen_US
dc.description.degreePh. D.en_US
dc.identifier.oclc19720228en_US
thesis.degree.namePh. D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.grantorVirginia Polytechnic Institute and State Universityen_US
thesis.degree.disciplineMining and Minerals Engineeringen_US
dc.contributor.committeechairKarmis, Michael E.en_US
dc.contributor.committeememberFaulkner, G. J.en_US
dc.contributor.committeememberKarfakis, M.en_US
dc.contributor.committeememberHaycocks, C.en_US
dc.contributor.committeememberLucas, J. R.en_US
dc.type.dcmitypeTexten_US


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