Tilt test (geotechnical engineering)
In geomechanics a tilt test is a simple test to estimate the shear strength parameters of a discontinuity[1][2]. Two pieces of rock containing a discontinuity are held in hand or mounted in test equipment with the discontinuity horizontal. The sample is slowly tilted until the top block moves. The angle with the horizontal at inset of movement is the so-called tilt-angle. The size of the specimen is limited to 10-20 cm for hand-held tests, while machine-operated tilt test equipment may handle up to meter-sized samples.
Tilt-angle
The tilt-angle equals the material friction of the discontinuity wall plus the roughness i-angle (tilt-angle = φwall material + i) if no real cohesion is present (i.e. no cementing or gluing material between the two blocks), the asperities do not break, and the walls of the discontinuity are completely fitting, while if the walls of the discontinuity are completely non-fitting, the tilt-angle equals the friction of the material of the discontinuity walls (tilt-angle = φwall material). If cementation or gluing material is present or asperities break, the tilt-angle represents a combination of the (apparent or real) cohesion and the friction along the discontinuity.
References
- ^ Hoek, E.; Bray, J. (1974). Rock slope engineering. London: Institute of Mining and Metallurgy. p. 358. ISBN 978-0419160106.
- ^ Xian-Qin, H.; Cruden, D.M. (1992). "A portable tilting table for on-site tests of the friction angles of discontinuities in rock masses". Bulletin Of the International Association of Engineering Geology. 46 (1): 59–62. doi:10.1007/BF02595034.
Further reading
Barton, N.R. (2008). "Shear Strength of Rockfill, Interfaces and Rock Joints, and their Points of Contact in Rock Dump Design". In Fourie, A. (ed.). Rock Dumps 2008. Perth, Australia. pp. 3–17. ISBN 978-0-9804185-3-8. {{cite conference}}: Unknown parameter |booktitle= ignored (|book-title= suggested) (help)
Price, D.G. (2008). De Freitas, M.H. (ed.). Engineering Geology: Principles and Practice. Springer. p. 450. ISBN 3-540-29249-7.