SCALE-MODELLING OF FLUID FLOW IN GEOTECHNICAL CENTRIFUGES

ROY BUTTERFIELD

ABSTRACT: Geotechnical centrifuges enable prototype-magnitude effective stresses to be generated in small-scale soil models, a necessary condition for using them to predict prototype behaviour. The paper presents a thorough dimensional analysis of the modelling process. The general relationships between soil-particle size, pore-fluid viscosity and time-scaling processes which are necessary (in addition to effective-stress consistency), to ensure correct Reynolds Number modelling are presented in detail. The conditions for valid modelling of consolidation and accelerating-particle processes are also defined and discussed. Some historical errors are noted together with an analysis of the shortcomings of the use of 'prototype soil ' in the model and oversimplified fluid viscosity scaling. A new pseudo-prototype concept is also introduced. This defines the prototype soil which is actually being modelled in a centrifuge test, enabling it to be com- pared with the one intended.

Key words: centrifuge, dimensional analysis, modelling, particle-size, viscosity (IGC: D7/E14)