2.1 Centrifuge

Physical modelling plays an important role in geotechnical engineering as the following uses:

1. Inspection of development processes of phenomena
2. Parametric studies
3. Investigation of new phenomena
4. Verification of analytical or numerical method

However, it could not be simulated properly, with model tests under the ordinary gravity field, this is mainly because self-weight forces are the dominant load in geotechnical engineering and the confining pressures generated by them govern the behaviour of the soil mass. The details of this dependency of a soil behaviour on the stress level and history are explained in the following section.
Importance of self-weight induced stresses in the behaviour of large soil mass can be  understood from the figures shown below. In the figures, the distributions of the stress field in the soil are examined in a small model. In this case, the stresses induced by a footing pressure are much larger than that by gravity. Hence the stress condition and stress paths in the small model are different from those in prototype.

In order to replicate the gravity-induced stresses of a prototype in a 1/n reduced model, it is necessary to test the model in a gravitational field n times larger than that of prototype. A centrifuge is thought to be the most convenient tool to make a high acceleration field in a model. This idea was applied for the first time in 1930s, in the field of the geotechnical engineering, by P. B. Bucky (1931) and G. I. Pokrovsky (1932). Since then, a number of geotechnical centrifuges have been installed in research institutes all over the world. Centrifuge modelling has become one of the powerful tools for physical modelling.

Mikasa, M. and Takada, N. (1973) : Significance of centrifuge model test in soil mechanics, Proc. of 8th ICSMFE, Vol. 1, pp. 273-278.

Kimura, T. and Kusakabe, O. (1987) : Centrifuge model tests, 2. Introduction, Tsuchi-to-kiso,Vol. 35, No. 11, pp. 68-74 (in Japanese).