ISRM Suggested Method for Determining the Basic Friction Angle of Planar Rock Surfaces by Means of Tilt Tests
The basic friction angle plays a key role when estimating the shear strength of discontinuities for rock engineering projects, since a large body of research has shown that rock joint shear strength models that consider it are able to provide realistic results (Barton 1973; Barton and Choubey 1977; Kulatilake et al. 1995; Grasselli and Egger 2003; Xia et al. 2014; Tang and Wong 2016).
The concept behind the basic friction component of shear strength is related to the angle of repose observed for solid bodies on inclined surfaces or granular materials. Based on this analogy, the basic friction angles of planar rock surfaces can be determined by means of tilt tests. Gravity provides both the shear and normal stress components in tilt tests. In this suggested method, the testing device, specimen preparation, shapes and sizes, and testing procedure are described. In addition, other issues related to the tilt test and basic friction angle, such as the effect of vibrations...
KeywordsTilt test Basic friction angle Planar rock surface Laboratory testing Joint strength
The authors acknowledge the five reviewers (Dr. Nick Barton, Prof. Anna Maria Ferrero, Dr. Dong-Hyun Kim, Dr. Fredrik Johansson and Dr. Mostafa Sharifzadeh) for their critical reviews and constructive comments that led to significant improvements to the Suggested Method. The authors also thank all members of the ISRM Testing Commission for guidance and, particularly, Dr. Suseno Kramadibrata for his useful comments and Prof. Xia-Ting Feng, for his kind help throughout the review process of the Suggested Method. The authors finally acknowledge the members of the ISRM board and particularly Doug Stead and Petr Konicek for final corrections to this document.
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