Experimental observations and variability assessment of the basic friction angle of rock and concrete saw-cut surfaces under different testing conditions

• Published in: Arabian journal of geosciences 2022-02, Vol.15 (3), Article 248
• Main Authors: Pérez-Rey, Ignacio, Ivars, Diego Mas, Alejano, Leandro R., Arzúa, Javier
• Format: Article
• Language: English
• Subjects: Angle of repose; Attitude (inclination); Basic friction angle; Concrete; Crystallization; Discontinuity; Earth and Environmental Science; Earth science; Earth Sciences; Environmental conditions; Environmental effects; Friction; Granular materials; Humidity; Laboratories; Laboratory tests; Micro-roughness; Moisture content; Ocean surface topography; Original Paper; Parameters; Rocks; Shear strength; Testing; Tests; Water content; Wear
• ISSN: 1866-7511; 1866-7538; 1866-7538
• DOI: 10.1007/s12517-022-09577-3

Prediction of the shear strength of rock discontinuities is usually performed by resorting to empirical shear strength criteria that depend on different inputs, some of which can be estimated through laboratory tests. Even though these tests are usually developed with rock materials, concrete is often used to make joint replicas. A relevant parameter among those affecting the shear strength behaviour of discontinuities is the basic friction angle, representative of a planar surface and clearly related to the angle of repose of granular materials and solid bodies placed on an inclined plane. Many efforts were carried out by several researchers to suggest a straightforward and simple procedure to obtain this parameter for rock surfaces in a rigorous way by means of tilt tests, which crystallized into an ‘ISRM Suggested Method’. Aiming at complementing basic friction angle results from tests developed under different scenarios and with different materials (rock and concrete), this paper presents an experimental program encompassing more than 500 tilt tests carried out in dry, water-saturated and submerged conditions. Complementarily, a detailed assessment of both rock and concrete surfaces was carried out, in order to study the possible implications between surface topography, wear, mass loss and evolution of the basic friction angle with repeated testing. The basic friction angle of a granite and a concrete has been estimated for three different testing scenarios related to the water content of specimens. A relevant effect of the environmental conditions of the laboratory (humidity and temperature) on results has been detected. Experimental conclusions are complemented with a statistical assessment of results.