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Title: Partial saturation as a means of liquefaction mitigation in granular soil
Author: Copp, D. M.
Awarding Body: University of Wales Swansea
Current Institution: Swansea University
Date of Award: 2003
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Liquefaction has been a widely-researched and controversial branch of geotechnical engineering after it first came to prominence during the Niigata/Alaskan earthquakes of 1964. Since then, engineers have developed various methods of liquefaction mitigation, in which soil improvement techniques are employed in order that the local development of those criteria which affect a soil's liquefaction susceptibility are inhibited. The most important of these criteria are rises in pore-water pressure, which reduce the capability of the soil to bear an effective stress, thereby compromising its engineering strength. If the excess pore-water pressure at a given point rises to a value which is numerically equal to the overburden stress at that point, then the effective stress will fall to zero, and the soil will behave as a viscous liquid, a condition which will have catastrophic consequences for both surface and sub-surface constructions. This thesis proposes the use of partially saturated soil as a means of liquefaction mitigation, as opposed to the more invasive methods which are currently advocated in the geotechnical engineering industry. Partial saturation increases the matric suction within a given soil. The matric suction, being a tensile stress, increases the strength of the soil, and reduces its ability to undergo shear strains. It is these shear strains which cause pore-water pressures to rise when a loosely bound, undrained soil mass is subjected to an earthquake loading. Newly-formulated methods of preparing loose, partially saturated sand specimens for triaxial testing are presented, as well as dynamic studies using a one-dimensional oscillator. The use of ProShake, a commercially-available software package, is also well documented, with special reference to change to the low-stiffness soil parameters caused by the introduction of partial saturation. Finally, the use of the author's own FORTRAN program, LSC, illustrates the concept of 'liquefaction sequencing', which is also presented here for the first time.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available