The Strength and Dilatancy of Geomaterials
Abstract
The speaker’s 1986 paper in Geotechnique on “The strength and dilatancy of sands” was well received, and has accumulated many citations. In this lecture, the speaker will look back at the fundamentals of the strength of a wider range of geomaterials including clays and jointed rocks. The shearing performance of each class of material can best be understood in terms of the interlocking of its component pieces, and their crushing strength. Different formulations are appropriate for the different materials, but the inability of the linear Mohr-Coulomb model to capture the strength of dilatant geomaterials is evident in each case.
An important application is the vertical bearing capacity of a spread foundation: an analysis using the speaker’s 1986 formulation is shown to have been validated in model tests conducted by Dr C. K. LAU who is well known locally in the field of geotechnics. However, in other applications such as slopes and retaining walls, the repeated application of stress ratios in excess of their critical state value leads to cyclic dilation and softening to that critical state strength. The significance of all this to engineering practice will be open to discussion.
About the speaker
Prof. Malcolm Bolton received his MSc in Structural Engineering from the University of Manchester and his PhD in Soil Mechanics from the University of Cambridge. His academic career in Geotechnical Engineering started in the University of Manchester Institute of Science and Technology, where he helped to develop the UK’s first geotechnical centrifuge. He returned to the University of Cambridge in 1980, where he ultimately became the Professor of Soil Mechanics, the Director of the Schofield Centre for Geotechnical Process and Construction Modelling, and the Head of the Geotechnical and Environmental Research Group in the Department of Engineering. In accordance with the University Statutes he retired in 2013.
Prof. Bolton was also the former HKUST IAS Senior Visiting Fellow. Prof. Bolton is elected 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 the founding chairman of the ISSMGE Technical Committee on Geo-Mechanics from Micro to Macro (GM3). He has collaborated on piles with the Giken Limited 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.
