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Three possible mechanisms for the onset of excess pore water pressure generation due to seismic excitation of saturated soil are investigated using downhole array data from sixteen real earthquakes. The downhole data are used to synthesize both stress and strain at various depths within the ground. Stresses, strains and dissipated energy are then investigated as potential liquefaction trigger mechanisms. The hypothesis that the shear strain threshold is a liquefaction trigger mechanism is strongly supported by the results presented here. In all but one case the shear strain threshold accurately predicts the time of pore pressure rise for real earthquakes in the field. Additionally, the onset of energy dissipation is found to signal the initial rise in measured excess pore pressure remarkably accurately. The results suggest a fundamental link between Nemat-Nasser and Shokooh's pore pressure - dissipated energy.density relationship (1979) and Mindlin and Deresiewicz's (1953) theoretical strain threshold. Mindlin and Deresiewicz's work (1953) defined a theoretical strain threshold as the mechanism for the onset of gross sliding, and 'its associated energy dissipation'. Therefore the onset of energy dissipation constitutes a second, independent verification of the strain threshold hypothesis. The relationship between stress invariants and pore pressure increase is less clear. To date there does not appear to be an acceptable theory that describes a trigger mechanism in terms of stress alone.

An experimental investigation was conducted on the static liquefaction behaviour of very loose lightly cemented sands. Undrained and drained triaxial compression tests, one dimensional consolidation, high stress compression, and unconfined compression tests were performed on artificially prepared lightly cemented loose samples with cement-sand ratios of 2, 4 and 6%. Additional tests were also conducted on uncemented samples prepared at the same initial void ratio as the cemented samples. Besides the influence of degree of cementation, the effects of void ratio and confining pressure on the liquefaction potential of cemented sands were examined. The aim of this study is to make significant contribution to the understanding of static liquefaction failures in lightly cemented sands. It is shown that cementation could increase the initial stiffness and yield strength of cemented sands but its effect might decrease considerably after the peak strength because of destruction of the cementation bond. The response of cemented sands at lower cement contents was very similar to the response of loose sands and behaviour approached the response of medium to dense sands with increase in the degree of cementation. It is also shown that degree of cementation has a significant influence on liquefaction resistance. Even though the presence of small amounts of cementation did not prevent liquefaction failure, the liquefaction resistance of cemented sands generally increased for higher degrees of cementation. The consolidation, high stress compression and unconfined compression tests demonstrated the effect of cementation in increasing both the stiffness and strength of cemented sands. The unconfined compression strength increased approximately linearly with the increase in cement content. The rate of strength gain increased with an increase in the dry density of the compacted sample, indicating that the cementation was more for denser samples.

An experimental investigation was conducted on the static liquefaction behaviour of very loose lightly cemented sands. Undrained and drained triaxial compression tests, one dimensional consolidation, high stress compression, and unconfined compression tests were performed on artificially prepared lightly cemented loose samples with cement-sand ratios of 2, 4 and 6%. Additional tests were also conducted on uncemented samples prepared at the same initial void ratio as the cemented samples. Besides the influence of degree of cementation, the effects of void ratio and confining pressure on the liquefaction potential of cemented sands were examined. The aim of this study is to make significant contribution to the understanding of static liquefaction failures in lightly cemented sands. It is shown that cementation could increase the initial stiffness and yield strength of cemented sands but its effect might decrease considerably after the peak strength because of destruction of the cementation bond. The response of cemented sands at lower cement contents was very similar to the response of loose sands and behaviour approached the response of medium to dense sands with increase in the degree of cementation. It is also shown that degree of cementation has a significant influence on liquefaction resistance. Even though the presence of small amounts of cementation did not prevent liquefaction failure, the liquefaction resistance of cemented sands generally increased for higher degrees of cementation. The consolidation, high stress compression and unconfined compression tests demonstrated the effect of cementation in increasing both the stiffness and strength of cemented sands. The unconfined compression strength increased approximately linearly with the increase in cement content. The rate of strength gain increased with an increase in the dry density of the compacted sample, indicating that the cementation was more for denser samples.

An experimental investigation was conducted on the static liquefaction behaviour of very loose lightly cemented sands. Undrained and drained triaxial compression tests, one dimensional consolidation, high stress compression, and unconfined compression tests were performed on artificially prepared lightly cemented loose samples with cement-sand ratios of 2, 4 and 6%. Additional tests were also conducted on uncemented samples prepared at the same initial void ratio as the cemented samples. Besides the influence of degree of cementation, the effects of void ratio and confining pressure on the liquefaction potential of cemented sands were examined. The aim of this study is to make significant contribution to the understanding of static liquefaction failures in lightly cemented sands. It is shown that cementation could increase the initial stiffness and yield strength of cemented sands but its effect might decrease considerably after the peak strength because of destruction of the cementation bond. The response of cemented sands at lower cement contents was very similar to the response of loose sands and behaviour approached the response of medium to dense sands with increase in the degree of cementation. It is also shown that degree of cementation has a significant influence on liquefaction resistance. Even though the presence of small amounts of cementation did not prevent liquefaction failure, the liquefaction resistance of cemented sands generally increased for higher degrees of cementation. The consolidation, high stress compression and unconfined compression tests demonstrated the effect of cementation in increasing both the stiffness and strength of cemented sands. The unconfined compression strength increased approximately linearly with the increase in cement content. The rate of strength gain increased with an increase in the dry density of the compacted sample, indicating that the cementation was more for denser samples.

Thesis (M.S.)--West Virginia University, 2007. / Title from document title page. Document formatted into pages; contains vii, 66 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 55-57).

Thesis (M.S.)--West Virginia University, 2001. / Title from document title page. Document formatted into pages; contains ix, 100 p. : ill. Includes abstract. Includes bibliographical references (p. 64-66).

Thesis (M.S.)--West Virginia University, 2000. / Title from document title page. Document formatted into pages; contains xvi, 182 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references (p. 98-100).

Thesis (Ph. D.)--Lehigh University, 1996. / Degree awarded in October 1996. Two separate papers. Includes vita. Bibliography: leaves 45-47; 130-133.