Malcolm Bolton
Centrifuge modelling: expecting the unexpected
Abstract
The unique advantage of physical modelling is that, unlike all forms of numerical simulation, it has the capacity to surprise its users with behaviour they would not have imagined. And the particular advantage of centrifuge testing is that observations are made on chosen soils, in a small format so that experiments can readily be repeated, and at magnitudes of stress and strain appropriate to field scale. However, it is the reasonable desire of centrifuge testers to represent their facilities as providing unambiguous predictions of field-scale performance through the application of accepted scaling laws, so as to recruit clients who will pay for such services. These diverse propositions create grounds for misunderstanding. Is centrifuge testing a cutting-edge research methodology capable of overthrowing conventional wisdom, or is it a well-understood tool capable of unambiguously recreating field-scale behaviour? This question sets the theme for the paper. In attempting to answer it, a variety of geotechnical modelling issues will be explored, including cyclic shearing and excess pore pressures, localisation and cracking, creep and strain-rate effects, and the possible influence of grain size and soil structure. In doing so, the key concept will be that of a behavioural mechanism. Weaker associations that may be made between a model, its prototype and a real field scale structure will then be scrutinised
Biography
Professor Malcolm Bolton FREng
Malcolm graduated in Engineering from Cambridge in 1967 with a leaning towards Civil Engineering. While pursuing research and teaching in both structures and soil mechanics at Manchester University he picked up the “bug” of centrifugal modelling from Andrew Schofield, assisting him in establishing the UK’s first geotechnical centrifuge in 1969. He returned to Cambridge in 1980 as a lecturer, later becoming Professor of Soil Mechanics, Director of the Schofield Centre for Geotechnical Process and Construction Modelling, and Head of the Geotechnical and Environmental Group. He retired from the University in 2013. He is an author of over 250 publications covering both the fundamental mechanics of granular materials and a wide variety of civil engineering applications from pipelines to tunnels, from foundations to embankments, and from earthquake effects to landslide hazard reduction. He was the founding chairman of the ISSMGE Technical Committee Geomechanics from Micro to Macro (GM3) dedicated to the practical application of a granular approach to soils, and the founding President of the International Press-in Association (IPA) dedicated to the hydraulic pressingin of piles for walls and foundations. He holds many awards from the British Geotechnical Society, the UK Institution of Civil Engineers, the Institution of Structural Engineers and the Canadian Geotechnical Society. He gave the 52nd BGA Rankine Lecture in 2012 on Performance-Based Design in Geotechnical Engineering and the 1st ISSMGE TC104 Andrew Schofield Lecturer in Paris in 2013. For more details see