Comparative tests of joint surface roughness of rocks from the McMurdo Sound area, Antarctica

• Main Author: Doolin, William Richard
• Other Authors: Selby, Michael J.
• Format: Thesis
• Language: English
• Published: The University of Waikato 2019
• Subjects: Antarctica; McMurdo Sound area; Antarctic; McMurdo Sound; Tilting; Barton; Pyramid; Antarc*
• Online Access: https://hdl.handle.net/10289/12828

Barton and co-workers (Barton, 1973, 1976; Barton and Choubey, 1977; Barton and Bandis, 1980; Bandis et al., 1981) have developed an empirical relationship to estimate the peak frictional resistance of a joint, which considers both the joint wall compressive strength and a joint surface roughness coefficient (JRC). Estimation of JRC can be achieved by comparing joint surface profiles with standard profiles of known JRC values. Alternatively, Barton proposes two simple index tests, tilt and pull (or push) tests, suitable for use in the field, from which JRC values can be back-calculated. Results from tests using these methods, conducted on 67 joints from six Antarctic lithologies, were statistically compared to results obtained from a numerical characterisation technique, involving computer digitisation, developed by Tse and Cruden (1979). While tilt and pull tests correlate well together, neither performs as reliably against the numerical technique as the profile comparison method. The Schmidt test hammer can be used to estimate compressive strength by quantitative relationships established with point load strength or uniaxial compressive strength. Its usefulness lies in its ability to test the narrow zone of influence of a joint wall. Basic friction angles can be simply estimated by a modified method of Stimpson (1981), involving the tilting of three cylindrical cores arranged as an elongated pyramid. Time series analysis of 125 joint surface profiles, using autocorrelation and spectral density functions, suggests that a majority of joint surfaces from all tested lithologies show a high amplitude periodic roughness with a wavelength of between 100 and 150 mm, upon which is superimposed one or more secondary, lower amplitude, periodic roughnesses, with a wavelength dependent on the degree of joint roughness, but most often around 12 mm.