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 the hand with the discontinuity horizontal. The sample is slowly tilted until the top block moves. The angle with the horizontal at start of movement is the so-called tilt angle.
Tilt angle
The tilt angle equals the material friction of the disconitnuity wall plus the roughness i-angle (tilt angle = φmaterial + i), only if no real cohesion is present (i.e. no glueing material between the two blocks), the asperities do not break, and the walls of the discontinuity are completely fitting. The tilt angle equals the friction of the material of the discontinuity walls if the walls of the discontinuity are completely non-fitting (tilt angle = φmaterial). In other cases, the tilt angle represents a combination of the (apparent) 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)