Improvement of Rock Bolt Profiles using Analytical and Numerical Methods
The anchorage capacity of fully grouted bolts has been studied for many years, however the bolt rib profile and its effect on bolt shear resistance is poorly understood. A new development in calculating load transfer capacity between two rib profiles of varying geometries is discussed. The derived mathematical equations presented calculate the stress distribution adjacent to the fully grouted bolt and bolt pull out force needed to fail the resin. The Fast Lagrangian Analysis Continua (FLAC) program was used to verify the calculations of stress within the resin. The novel idea of coupling the bolt geometry with the calculated stress provides another powerful tool to investigate the bolt profile configuration and its effects on the load transfer mechanism for the benefit of the mining industry.
Study of Load Transfer Capacity of Bolts Using Short Encapsulation Push Test
A series of laboratory experiments were conducted on a variety of bolt types to examine the load transfer capacities of different profiled bolts in short encapsulation push testing. A 70 mm section of 150 mm long bolt specimen was anchored in a 70 mm long stainless steel tube using full resin encapsulation. Six types of different profiled bolts and two non - profiled bolts were tested. Bolts with higher profile were in general found to have greater shearing resistance and higher stiffness than low profile bolts. Widely spaced profiles allow greater displacement at peak shear strength, and bolts with no profiles produced very little load transfer capability. Rough surfaced plain bolts showed a significant load transfer capability in comparison to a factory supplied smooth surface bolt which supports the belief that rusted bolts have higher load transfer capability that un-rusted bolt surfaces.
Investigation Of Fully Grouted Roof Bolts Installed Under In Situ Conditions
• A series of 24 pull tests of bolts installed fully grouted and overcored to leave 12 inches of grouted bolt. The tests compared the pull-out performance of offset-head roof bolts with that of standard 5/8-inch bolts; • A second series of 24 tests that compared the pull-out loads obtained by bolts installed with 1 ft of resin (a Short Encapsulation Pull Test or SEPT) to that of fully grouted bolts overcored to leave only 12 inches of grouted bolt, and; • An investigation into the pressures generated during the installation of fully grouted resin bolts.