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.
| Identifer | oai:union.ndltd.org:ADTP/234199 |
| Date | January 2006 |
| Creators | Mahony, Luke T, School of Mining, UNSW |
| Publisher | Awarded by:University of New South Wales. School of Mining |
| Source Sets | Australiasian Digital Theses Program |
| Language | English |
| Detected Language | English |
| Rights | Copyright Luke T Mahony, http://unsworks.unsw.edu.au/copyright |
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