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The lecture will discuss the measurement of suction (negative pore water pressure) in the laboratory and in the field. A high capacity tensiometer developed at Durham University capable of directly measuring 2MPa of negative pressure, well beyond the limit of conventional tensiometers (that are limited by cavitation to -100kPa) will be described.
Test results of measurements of soil water retention curves (the relationship between suction and water content) will be presented for a medium plasticity clay (Durham Till).
The results from laboratory tests will be compared with field measurements made in an instrumented embankment built near Newcastle. It will be shown that the soil water retention curves show distinct hysteresis, i.e. they follow different paths when subject to drying and wetting.
In addition, the overall curves shift with subsequent cycles of wetting and drying. This means that, for the same water content, suction values can vary very significantly, due to the history of drying and wetting to which the soil may have been subjected. This implies that water content may not be a good indicator of soil behaviour and we should consider measuring suction, since this is the variable that ultimately controls soil behaviour (strength and stiffness) in an unsaturated state.
The lecture also features presentations from the four finalists:
While the judges deliberate the audience will hear a special lecture by Professor David Toll of Durham University.
For more information and to book, please contact:
t: 0191 261 6080
The following materials are available for download:
David Toll is Professor of Engineering at Durham University. His research focus is on unsaturated and tropical soils, applied to studying climate impacts on slopes and foundations, rainfall-induced landslides and road construction materials for low volume roads.
He is a Fellow of the Institution of Civil Engineers and has been Chair of ICE North East and Chair of the Northern Geotechnical Group of BGA. He is Chair of Technical Committee 106 on Unsaturated Soils of the ISSMGE and also chairs Joint Technical Committee JTC2 on Geo-Engineering Data of FedIGS.
He has been recognised internationally by the award of Visiting Professor positions at the National University of Singapore and Tongji University, China and Visiting Fellowships at Nanyang Technological University, University of Western Australia, University of Newcastle, Australia and University of Sydney.