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Laboratory Studies of Yielding Rock Bolts.
Conway-JP; Dar-SM; Stears-JH; Mcwilliams-PC
NTIS: PB 245 560 :40 pages
The yielding-rock-bolt concept, as developed in South Africa, consists of a smooth-bore die or collar fitted to a standard rock bolt. Laboratory testing at the Bureau of Mines Spokane Mining Research Center under slow and fast strain rates showed that extrusion loads can be controlled by varying the configuration of the die bore and that theoretical analysis (using basically sachs' theory of wire drawing) predicts extrusion loads of the different die-bore configurations. A derived equation, based on this research, can be used for designed die-thread combinations for any desired extrusion load. Dynamic loading resulted in slightly higher loads (15 percent) than static loading. The strain hardening effect, which increases yield and ultimate strength, was partly offset by adiabatic heating of the threads, which decreases strength.
IH; Report of Investigations
NTIS Accession No.
NTIS: PB 245 560
Page last reviewed: May 5, 2020
Content source: National Institute for Occupational Safety and Health Education and Information Division