Professor Lord Robert Mair delivered the 20th Schiffman Lecture at the Geotechnical Colloquium, Cornell University in the USA.
The annual Cornell University Geotechnical Engineering Colloquium was created following a bequest by the late Dr. Robert L. Schiffman, Cornell Civil Engineering Class of 1944 and Professor Emeritus at the University of Colorado at Boulder, to give civil engineering students the opportunity to meet and to hear lectures delivered by distinguished geotechnical engineers and geoscientists.
Lord Mair’s lecture, titled ‘Lessons from Critical London Infrastructure Projects for Deep Circular Shaft Construction’, gave an overview of three recent critical London infrastructure projects from which important lessons have been learned. Until recently there have been relatively few well-documented case studies of deep circular shaft construction in clays, making it difficult for designers to calibrate estimates of associated ground movements and stresses induced in the shaft walls.
The Lecture described field observations of ground surface settlement during construction of 27 circular shafts, including some shafts measuring deeper than 40m. Careful interpretation of the field observations showed the importance of the shaft construction method on ground movements. Centrifuge model testing of the shafts in the 10m-diameter geotechnical centrifuge at the University of Cambridge – involving novel ‘in-flight’ excavation – provided further insight into the mechanisms of ground movement. The Lecture also presented data from innovative fibre optic monitoring of hoop stresses induced in shafts and conclusions for future design of circular shafts.
Lord Mair also presented the lecture at the University of California, Berkeley.