No description available.

Thesis (M.Eng.). / Written for the Dept. of Mechanical Engineering. Title from title page of PDF (viewed 2008/01/14). Includes bibliographical references.

This thesis describes the investigation of a non-destructive test method for integrity assessment of rock bolts using the resonance spectroscopy method. Although other methods exists these all present certain limitations. Initial experimental investigations included the assessment of a number of excitation mechanisms, namely, hammer tests, chirp tests and swept sine tests.

No description available.

M.Tech. / The field of study is of a multidisciplinary nature and involves aspects of Mechanical Engineering Design, Materials Technology and Rock Mechanics. When rock bursts occur the rock mass moves at high velocities and the resulting impulsive load often leads to brittle fracture of fully grouted steel bars. It was therefore decided to develop a new product that would combine the strength of steel and the yielding ability of polyurethane. Such a product is envisaged to play an important role in the correct design of tunnel support. In optimizing the design of a polyurethane and steel combination, three important parameters have to be optimized simultaneously...

No description available.

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.

Thesis (Ph. D.)--University of Nevada, Reno, 2008. / "May, 2008." Includes bibliographical references (leaves 136-142). Online version available on the World Wide Web.

Thesis (Ph. D.)--University of Nevada, Reno, 2006. / "December, 2006." Includes bibliographical references. Online version available on the World Wide Web.

Rock reinforcing elements provide a significant proportion of their ground control capability through offering resistance to shear movement of adjacent rock masses or blocks. This potential shear movement may take the form of sliding on horizontal bedding planes leading to strata bending; or block displacement along other geological structures such as joints or similar discontinuities. Much has been reported about this type of behaviour of rock bolts and other tendons, in theoretical concepts. However, there is a shortage of quality data available on the exact nature of this mechanism for shear resistance, and the role played by parameters such as pre-tensioning. A clearer understanding of the nature and significance of this type of behaviour has major implications for rock reinforcing materials and installation design. This thesis, which was supported by the Australian Coal Research Program (ACARP) describes the design, construction and commissioning of a laboratory testing facility at the School of Mining Engineering, University of New South Wales (UNSW), Australia and a subsequent testing program. The single failure plane design adopted in the test rig has been successful in allowing shear loading to be directly applied to fully installed rockbolts. Rockbolts were installed into an offset concrete rockmass, which consisted of two separate concrete samples that created a smooth shear plane surface. The reinforced samples were subjected to an applied shear load and critical parameters such as load and shear displacement were recorded. Influencing parameters such as concrete strength and applied pre-tension were altered and recorded to determine their effects on the overall shear performance of the sample. The failure mode of the rockbolts was also examined. The results indicate that a relative stronger rockmass material caused the rockbolt to fail within a lower shear displacement compared to a relatively weaker material. Also, a pre-tensioned rockbolt tended to resist shear displacement at least initially, until high shear loads developed. This phenomena is beneficial to ground support as less movement would tend to maintain integral strength of the rockmass. The use of strain-gauged rockbolts indicated as would be expected that the shear loading arrangement induced a compressive axial loading that tended to dissipate with distance from the shear surface.