Tasmania Chapter

52nd Rankine Lecture: Performance-based design in geotechnical engineering

Professor Malcolm Bolton

Performance-based design in geotechnical engineering by Professor Malcolm Bolton. Engineering design should consist of a sequence of decisions which should satisfy the client’s objective performance requirements. This lecture will argue that an assessment of geotechnical performance must involve ground displacements, and that the traditional approach of specifying safety factors is potentially wasteful. In particular, the Limit State Design (LSD) approach adopted in the Eurocodes will be shown to lack objectivity and therefore to be inadequate to the needs of clients and society at large. Improvements will be proposed through the adoption of Mobilizable Strength Design (MSD) principles in which the designer explicitly considers the stress-strain behaviour of the ground. Newly published databases offer a more reliable framework for this assessment. Central to the development of MSD is the specification of deformation mechanisms for various classes of geo-structure, obtained from field or model observations. Formulae for displacements are then derived by applying conservation of energy to the deformation mechanism. Design decisions can then be taken in the light of estimated deformations before any later checks which might be made by Finite Element Analysis (FEA). This also ensures that the intended design performance can be checked by monitoring during construction. Applications of MSD include a wide range of slopes, earth retaining structures and foundations: a few will be shown in detail.

Speaker Biography

Malcolm Bolton is Professor of Soil Mechanics at Cambridge University, and has been Director of the Schofield Centre for Geotechnical and Construction Modelling since 1995. He is a Fellow of the Royal Academy of Engineering and holds various prizes of the UK Institutions of Civil and Structural Engineering, the British Geotechnical Association and the Canadian Geotechnical Society. He was founding chairman of the ISSMGE Technical Committee on Geo-Mechanics from Micro to Macro (GM3). He has collaborated on piles with the Giken company of Japan for 18 years, and is the founding chairman of the International Press-In Association. He served on the Slope Stability Technical Review Board for the Hong Kong Government, and acts as a consultant in relation to soil-pipeline interactions on the sea bed. He helped to draft BS8002 Earth Retaining Structures, and has over 220 publications on topics ranging from fundamental soil mechanics to a wide variety of geotechnical engineering applications.

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