Geomechanical characterisation of discontinuous greywacke from the Wellington region based on laboratory testing

Greywacke rock masses are the most prominent (∼20%) bedrock type across New Zealand. This paper reviews the publicly available laboratory testing data on the geomechanical properties of greywacke from the Wellington region and compares the results with two recent studies. This includes compilations...

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Bibliographic Details
Published in:New Zealand journal of geology and geophysics 2022-04, Vol.65 (2), p.265-282
Main Authors: Brideau, Marc-André, Massey, Christopher I., Carey, Jonathan M., Lyndsell, Barbara
Format: Article
Language:English
Subjects:
Bedrock
Cores
deformability
discontinuities
Discontinuity
discontinuous rock mass
Geomechanics
Greywacke
Intact rock
Laboratories
Laboratory tests
Mechanical properties
Modulus of elasticity
Parameters
Poisson's ratio
Properties
Rock masses
Rocks
strength
Testing
Weathering
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Summary:Greywacke rock masses are the most prominent (∼20%) bedrock type across New Zealand. This paper reviews the publicly available laboratory testing data on the geomechanical properties of greywacke from the Wellington region and compares the results with two recent studies. This includes compilations of density, unconfined compressive strengths (UCS), tensile strengths, Poisson's ratio, Young's Modulus, and m i factor. This paper also presents the first published geomechanical data from a cataclasite zone in the greywacke of the Wellington region. The overall results presented in this paper highlight the influence of both weathering and discontinuities on the geomechanical properties derived from the testing of core samples. The results are discussed in the context of sampling bias, scale effects and recent developments in the geomechanical characterisation of discontinuous rock. Two different approaches for characterising the rock mass geomechanical properties of greywacke at the project-scale are presented. The first approach uses the geological strength index (GSI) as the main parameter to capture the change in rock mass character with depth while the UCS remains constant. The second approach uses the UCS as the main parameter to capture the change in rock mass character with depth, while the GSI value remains constant.
ISSN:0028-8306
1175-8791
DOI:10.1080/00288306.2020.1853181