Analysis of the dynamic behaviour of the hangingwall beam during a seismic event

dc.contributor.advisorMartin, JBen_ZA
dc.contributor.authorDaehnke, Aen_ZA
dc.date.accessioned2014-10-11T12:16:25Z
dc.date.available2014-10-11T12:16:25Z
dc.date.issued1992en_ZA
dc.descriptionBibliography: leaves 68-72.en_ZA
dc.description.abstractIn a deep-level gold mine planes of weakness oriented parallel to the reef allow the hangingwall to separate from adjacent rock strata. The hangingwall then acts as a separate beam supporting only its selfweight. Mining-induced near vertical shear fractures divide the hangingwall beam into distinct blocks of relatively intact material. The objective of this study is to investigate the response of the isolated hangingwall beam during a seismic event. The study is particularly concerned with the global, resonant behaviour of the hangingwall and local shear or crushing failure of the rock at the shear fractures is not considered. A finite element program is developed to compute the hangingwall response during seismicity. The response is normalised, thus permitting the response spectrum method to describe maximum hangingwall motions during a seismic event at various beam lengths. By comparing the response spectrum describing a single-degree-of-freedom (SDOF) system with the spectrum of the hangingwall, it is evident that, although the hangingwall response spectrum is shifted to a higher frequency and velocity domain, the shapes of the two spectra are essentially the same. The frequency and velocity shift is calculated for 15 seismic events and empirical rules are developed to quantify the spectral shift for a wide range of event magnitudes. Unlike the spectrum describing hangingwall motions, the construction of a SDOF response spectrum is computationally cheap and is standard practice in earthquake engineering. By applying the empirical rules the seismologist can extrapolate the SDOF spectrum to estimate maximum hangingwall motions due to a seismic event and critical beam lengths which are prone to resonance. The effect on the response of the hangingwall supported by backfill consisting of dewatered and cemented tailings is evaluated. It is shown that a fill-to-face lag of less than 5m reduces hangingwall motions considerably. Further, at small strains the stiffer cemented tailings provide superior support than that offered by comparatively soft dewatered tailings. A chart is presented which correlates event magnitudes to critical beam lengths prone to resonance.en_ZA
dc.identifier.apacitationDaehnke, A. (1992). <i>Analysis of the dynamic behaviour of the hangingwall beam during a seismic event</i>. (Thesis). University of Cape Town ,Faculty of Engineering & the Built Environment ,Department of Mechanical Engineering. Retrieved from http://hdl.handle.net/11427/8383en_ZA
dc.identifier.chicagocitationDaehnke, A. <i>"Analysis of the dynamic behaviour of the hangingwall beam during a seismic event."</i> Thesis., University of Cape Town ,Faculty of Engineering & the Built Environment ,Department of Mechanical Engineering, 1992. http://hdl.handle.net/11427/8383en_ZA
dc.identifier.citationDaehnke, A. 1992. Analysis of the dynamic behaviour of the hangingwall beam during a seismic event. University of Cape Town.en_ZA
dc.identifier.ris TY - Thesis / Dissertation AU - Daehnke, A AB - In a deep-level gold mine planes of weakness oriented parallel to the reef allow the hangingwall to separate from adjacent rock strata. The hangingwall then acts as a separate beam supporting only its selfweight. Mining-induced near vertical shear fractures divide the hangingwall beam into distinct blocks of relatively intact material. The objective of this study is to investigate the response of the isolated hangingwall beam during a seismic event. The study is particularly concerned with the global, resonant behaviour of the hangingwall and local shear or crushing failure of the rock at the shear fractures is not considered. A finite element program is developed to compute the hangingwall response during seismicity. The response is normalised, thus permitting the response spectrum method to describe maximum hangingwall motions during a seismic event at various beam lengths. By comparing the response spectrum describing a single-degree-of-freedom (SDOF) system with the spectrum of the hangingwall, it is evident that, although the hangingwall response spectrum is shifted to a higher frequency and velocity domain, the shapes of the two spectra are essentially the same. The frequency and velocity shift is calculated for 15 seismic events and empirical rules are developed to quantify the spectral shift for a wide range of event magnitudes. Unlike the spectrum describing hangingwall motions, the construction of a SDOF response spectrum is computationally cheap and is standard practice in earthquake engineering. By applying the empirical rules the seismologist can extrapolate the SDOF spectrum to estimate maximum hangingwall motions due to a seismic event and critical beam lengths which are prone to resonance. The effect on the response of the hangingwall supported by backfill consisting of dewatered and cemented tailings is evaluated. It is shown that a fill-to-face lag of less than 5m reduces hangingwall motions considerably. Further, at small strains the stiffer cemented tailings provide superior support than that offered by comparatively soft dewatered tailings. A chart is presented which correlates event magnitudes to critical beam lengths prone to resonance. DA - 1992 DB - OpenUCT DP - University of Cape Town LK - https://open.uct.ac.za PB - University of Cape Town PY - 1992 T1 - Analysis of the dynamic behaviour of the hangingwall beam during a seismic event TI - Analysis of the dynamic behaviour of the hangingwall beam during a seismic event UR - http://hdl.handle.net/11427/8383 ER - en_ZA
dc.identifier.urihttp://hdl.handle.net/11427/8383
dc.identifier.vancouvercitationDaehnke A. Analysis of the dynamic behaviour of the hangingwall beam during a seismic event. [Thesis]. University of Cape Town ,Faculty of Engineering & the Built Environment ,Department of Mechanical Engineering, 1992 [cited yyyy month dd]. Available from: http://hdl.handle.net/11427/8383en_ZA
dc.language.isoeng
dc.publisher.departmentDepartment of Mechanical Engineeringen_ZA
dc.publisher.facultyFaculty of Engineering and the Built Environment
dc.publisher.institutionUniversity of Cape Town
dc.subject.otherMechanical Engineeringen_ZA
dc.titleAnalysis of the dynamic behaviour of the hangingwall beam during a seismic eventen_ZA
dc.typeMaster Thesis
dc.type.qualificationlevelMasters
dc.type.qualificationnameMScen_ZA
uct.type.filetypeText
uct.type.filetypeImage
uct.type.publicationResearchen_ZA
uct.type.resourceThesisen_ZA
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