Tilt test (geotechnical engineering)
In geomechanics a tilt test is a simple test to estimate the shear strength parameters of a discontinuity. 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 meter-sized samples.
Tilt angle
The tilt angle equals the material friction of the disconitnuity wall plus the roughness i-angle (tilt angle = φmaterial + 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 = φmaterial). If cementation or glueing material is present or asperities break, the tilt angle represents a combination of the (apparent or real) cohesion and friction of the discontinuity.
References
Further reading
Barton, N.R. "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)