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Title: Performance of unsaturated soil under monotonic and repeated loading
Author: Thom, Rachael
ISNI:       0000 0001 3516 9824
Awarding Body: Queen's University Belfast
Current Institution: Queen's University Belfast
Date of Award: 2008
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Unsaturated soils constitute a large proportion of the foundation materials supporting infrastructure throughout the world and they are subject to various loading conditions. The research into the behaviour of unsaturated soils has been ignored for many centuries; however the recent years have witnessed a surge of research activities looking into various aspects. The present research reported in this thesis places emphasis on the perfomlance of unsaturated soils under repeated loading. As part of the research, a series of monotonic and repeated load triaxial tests were perfonned on samples of kaolin clay prepared to various compaction water contents, 22%, 25%, '28% and 31% and two different compression pressures, 400kPa and 800kPa. Undrained tests were conducted in a newly developed simple triaxial cell for testing unsaturated soil under repeated loading with hydraulic loading system, hall-effect transducers for on-sample strain measurements and thennocouple psychrometer for suction measurements. Drained tests were conducted in twin-cell stress path apparatus with controlled suction by axis translation teclmique. The main findings of the research provide a remarkable insight into the influence of suction, and more imp011antly the degree of saturation, on the permanent defonnation and resilient behaviour of unsaturated compacted kaolin. At high suctions repeated loading was found to have a positive effect on the soil pelfoIl1lance. However, at low suction, repeated loading had a detrimental effect on the strength and stiffness of unsaturated soil, under both drained and undrained conditions. An important outcome of the research is the progression of permanent defoIl11ation throughout repeated loading with no asymptotic value ever being reached, particularly at loading amplitudes of more than 70% of the failure load.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available