Peak Shear Strength of Natural, Unfilled Rock Joints in the Field Based on Data from Drill Cores – A Conceptual Study Based on Large Laboratory Shear Tests

Abstract

Significant uncertainties remain regarding the field assessment of the peak shear strength of rock joints. These uncertainties mainly originate from the lack of a verified methodology that would permit prediction of rock joints’ peak shear strength accounting for their surface area, while using information available from smaller samples. This paper investigates a methodology that uses objective observations of the 3D roughness and joint aperture from drill cores to predict the peak shear strength of large natural, unfilled rock joints in the field. The presented methodology has been tested in the laboratory on two natural, unfilled rock joint samples of granite. The joint surface area of the tested samples was of approximately 500 × 300 mm. In this study, the drill cores utilised to predict the peak shear strength of the rock joint samples are simulated based on a subdivision of their digitised surfaces obtained through high-resolution laser scanning. The peak shear strength of the tested samples based on the digitised surfaces of the simulated drill cores is predicted by applying a peak shear strength criterion that accounts for 3D roughness, matedness, and specimen size. The results of the performed analysis and laboratory experiments show that data from the simulated drill cores contain the necessary information to predict the peak shear strength of the tested rock joint samples. The main benefit of this approach is that it may enable the prediction of the peak shear strength in the field under conditions of difficult access.

Using PFC2D to simulate the shear behaviour of joints in hard crystalline rock

“…In rock mechanics, it is necessary to be able to assess the shear strength of rock joints in order to solve different rock mechanical problems; this includes, for example, slope stability, block and arching stability in tunnels and the sliding stability of dams. In recent decades, various attempts have been made to develop empirical and analytical criteria to increase the understanding of the peak shear strength of rock joints (e.g., Patton 1966;Ladanyi and Archambault 1969;Barton and Choubey 1977;Grasselli and Egger 2003;Johansson and Stille 2014;Yang et al 2016;Casagrande et al 2018;Ban et al 2020;Ríos-Bayona et al 2021, 2022.…”