• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • No language data
  • Tagged with
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

DESIGN METHODS FOR ROCK BOLTS USING IN-SITU MEASUREMENT FROM UNDERGROUND COAL MINES

Kostecki, Todd 01 May 2019 (has links)
The research in this dissertation was undertaken because of a need for a more accurate, reliable and relatively simple method for determining the combined loading (i.e., axial, flexure and shear) along rock bolts. This combined load determination and understanding also resulted in a relatively simple and reliable new rock bolt design methodology. The new design method was based on a clearer understanding of the actual loading along a grouted rock bolt. To accomplish these research goals, double shear tests were conducted in the lab with reinforced concrete specimens, and field trials were conducted in room and pillar coal mines, with the aim to measure in-situ rock shear. Strain measurements were obtained using rock bolts instrumented with optical fibers that possessed high spatial resolution (≈ 1.25 – 2.5 mm). Corroboration with a past database of rock bolt measurements in shale aided in the deduction of the final support design method. The scientific contributions from this research include the conceptualization of a ground reaction curve that considers time effects such as rock relaxation, long term weakening effects, and lateral rock movement. A new explanation as to why rock bolts creep in practice (i.e., dislocation creep) is described based upon field measurements, which also indicated that the process of in-situ rock shear involves slow episodic movements. Specifically, there are localized compression (i.e., rock pinch) and tensile zones (i.e., dilatation) prior to the occurrence of plastic relief (i.e., rock slip). Finally, the design method is developed using simple factors (i.e., strain and shape factors) and loading conditions (e.g., installed load, rock slip) that occurred throughout the rock bolt’s design life. This approach results in a methodology that considers effects on reinforcement with time and combined loadings. The method is then extended by producing survival and hazard functions for rock bolts to ultimately reduce risk associated with design.

Page generated in 0.03 seconds