3.2.3 Rotational acceleration and stress field

In centrifuge models, an arc length between two radial planes increases with an increase in radius, as shown in Fig. 1(a). This results in lateral expansion of the soil model. To keep lateral strain zero as depicted in the Fig. 1(b), arc lengths should be kept constant, which is, however, not possible. Therefore, magnitude of lateral acceleration should be evaluated. For example, for a model with half width of 10 cm and a centrifuge with an effective radius of 100 cm, the lateral acceleration is approximately 0.1 times the vertical acceleration. It is preferable to locate major events in the central region of the model where acceleration error is small.

Both acceleration and stress field are constant on any particular arc and both acceleration and stress increase with an increase in radius. Variation of vertical stress in the model is non-linear as seen in Fig. 1(c), whose tendency is different from that in the prototype. To make an error in stress profile less than 3 %, ratio of model depth to effective radius d_m / R_e is estimated less than 0.2.

Siddiquee, M.S.A., Tanaka, T. and Tatsuoka, F. (1992) : A numerical simulation of bearing capacity of footing on sand, Proc. of 27th. Annual Meet. JSSMFE, Vol. 2, pp. 1413-1416.

Ko, H.Y. (1988) : Summary of the state-of-the-art in centrifuge model testing, In Centrifuges in Soil Mechanics (eds Craig, W.H., James, R.G. and Schofield, A.N.), Balkema, Rotterdam, pp. 11-18.

Taylor, R.N. (1995) : Centrifuges in modelling: principles and scale effects, In Geotechnical Centrifuge Technology (ed Taylor, R.N.), Blackie Academic and Professional, Glasgow, pp. 19-33.

Phillips, R. (1995) : Centrifuges in modelling: practical consideration, In Geotechnical Centrifuge Technology (ed Taylor, R.N.), Blackie Academic and Professional, Glasgow, pp. 34-60.