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Title: The performance of foundations supported on unsaturated clay fill
Author: Cairns, P. T.
ISNI:       0000 0004 2722 483X
Awarding Body: Queen's University Belfast
Current Institution: Queen's University Belfast
Date of Award: 2012
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High numbers of deep depressions are found specifically within the immediate area of man);' main cities across the UK and are increasingly becoming the target of major reclamation schemes. Clayey fills are Jenerally placed and compacted in an unsaturated state to facilitate ease of placement and are commonly misconstrued to possess desirable features. However if the fill was to become saturated, the volumetric response whether swelling or collapse compression can induce excessive displacements within the soil. Such soil behaviour can potentially have a detrimental effect on suspended piled foundations. The present study carried out a physical small scale model of a single piled footing supported on a compacted clay bed, under a constant axial load and subjected to wetting. The project focused on the development of a novel chamber capable of testing large cylindrical un-engineered and engineered clay samples under suction controlled conditions and confining pressure. Element tests indicated that in both samples simultaneous axial yelling and lateral collapse occurred during wetting. LC yield loci were therefore considered separately in the axial and radial plane. An instrumented pile model was implemented into the main testing programme and its performance (relating to various methods of pile installation) was evaluated on the basis of axial load distribution and settlement determined from local strain instrumentation. Under wetting conditions a differing profile of axial displacement occurred within various clay bed zones causing variable development of skin friction along the pile shaft, resulting in pile uplift and excessive settlement throughout the period of wetting. Lateral swelling and collapsing was postulated to control intermittent load share at the pile-soil interface thus influencing the degree of axial displacement observed in clay bed. Pile performance is shown as dependent upon the magnitude of the foundation load, degree of initial adhesion, and compactive effort of the clay bed.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available