Thesis (Ph. D.)--School of Computing and Engineering and Dept. of Geosciences. University of Missouri--Kansas City, 2008. / "A dissertation in engineering and geosciences." Advisor: Anil Misra. Typescript. Vita. Title from "catalog record" of the print edition Description based on contents viewed Sept. 12, 2008. Includes bibliographical references (leaves 234-236). Online version of the print edition.

Thesis (Ph. D.)--University of Washington, 1996. / Vita. Includes bibliographical references (leaves [283]-293).

Thesis (Ph.D.)--Drexel University, 2010. / Includes abstract and vita. Includes bibliographical references (leaves 243-248).

Thesis (Ph. D.)--University of Texas at Austin, 2005. / Supervisor: Ellen M. Rathje. Vita. Includes bibliographical references.

No description available.

Liquefaction ls a phenomenon where a saturated soil can temporarily lose its shear strength during an earthquake as a result of the development of excess pore pressures. For the past 25 years since Iiquefaction phenomenon was first explained, it was thought to be mainly a problem with clean sand, and most of the research has focused on these soils. However, as case history information has come to light, it has become apparent that silty sands are commonly involved, and in some cases even silts. This has generated a need for knowledge about the response of silty sands and silts under seismic loading. Related to this issue is the question of how best to determine the Iiquefaction resistance of these soils in a practical setting. This research has the objectives of providing an understanding of the behavior of saturated silty sands under seismic loading, and developing a rational basis for the use of the Cone Penetration Test (CPT) to predict Iiquefaction resistance in these materials. The study is primarily experimental, relying on laboratory and field testing and the use of a unique, large scale calibration chamber. The calibration chamber allows the field environment to be duplicated in the laboratory where conditions can be closely controlled and accurately defined. One of the first problems to be overcome in the research was to determine how to prepare specimens of silty sands that would reasonably duplicate field conditions in both the small scale of the conventional laboratory tests, and the large scale of the calibration chamber. Out of four different methods explored, consolidation from a slurry proved to be best. Two silty sands were located which had the desired characteristics for the study. Field work, involving both the Standard Penetration Test (SPT) and CPT was done as part of this investigation. The behavior of the silty sands were determined in the laboratory from monotonic and cyclic loading tests. The test results show that the effect of fines is to reduce the cone penetration resistance, but not to affect the liquefaction resistance. The steady state shear strength of the soils seems to be correlated to the cone tip resistance, however, this correlation shows a higher steady state shear strength than those back figured from case history data. The results were also used to define state parameters for both of the soils tested. The state parameter was found to be a reliable index to the liquefaction potential and further study in this area is recommended. / Ph. D.

The 2010-2011 Canterbury, New Zealand, Earthquake Sequence (CES) resulted in a liquefaction dataset of unprecedented size and quality, presenting a truly unique opportunity to assess and improve the efficacy of liquefaction-analytics in the field. Towards this end, the study presented herein develops and analyzes a database of 10,000 high-quality liquefaction case histories resulting from the CES. The objectives of these analyses are varied, but underlying each is the desire to more accurately assess liquefaction hazard for civil infrastructure (i.e., to predict both the occurrence and damage-potential of soil liquefaction). Major contributions from this work include, but are not limited to: (1) the Liquefaction Potential Index (LPI), the state-of-practice framework for assessing liquefaction hazard, is shown to produce erroneous predictions for a significant percentage of the assessed case histories; (2) the cause of poor predictions is rigorously investigated and specific shortcomings of the LPI framework are identified; (3) based on the limitations identified, and using insights from historical data, a revised liquefaction hazard framework is developed; and (4) the revised framework is shown to assess liquefaction hazard more efficiently relative to both LPI and a competing alternative framework newly proposed in the literature. Ultimately, significant room for improvement remains with respect to accurate assessment of liquefaction hazard. The findings presented in this dissertation thus form the basis for future development of a further-improved framework. Moreover, a methodology is proposed by which improvements can be measured in a standardized and objective manner. / Ph. D. / Soil liquefaction is a common cause of ground failure during earthquakes and is directly responsible for tremendous damage to civil infrastructure. Manifestations of liquefaction include the occurrence of sand blows and lateral spread failures, settlement and tilting of structures, cracking of pavements, and failure of buried lifelines due to flotation or differential settlements, among others. These effects were vividly displayed during the 2010-2011 Canterbury, New Zealand, Earthquake Sequence (CES), which resulted in a liquefaction dataset of unprecedented size and quality, presenting a truly unique opportunity to advance the science of liquefaction hazard. Towards this end, the study presented herein develops and analyzes a database of 10,000 high-quality liquefaction case histories resulting from the CES. The objectives of these analyses are varied, but underlying each is the desire to more accurately assess liquefaction hazard for civil infrastructure (i.e., to predict both the occurrence and damage-potential of soil liquefaction). Major contributions from this work include, but are not limited to: (1) the Liquefaction Potential Index (LPI), the state-of-practice framework for assessing liquefaction hazard, is shown to produce erroneous predictions for a significant percentage of the assessed case histories; (2) the cause of poor predictions is rigorously investigated and specific shortcomings of the LPI framework are identified; (3) based on the limitations identified, and using insights from historical data, a revised liquefaction hazard framework is developed; and (4) the revised framework is shown to assess liquefaction hazard more efficiently relative to both LPI and a competing alternative framework newly proposed in the literature. Ultimately, significant room for improvement remains with respect to accurate assessment of liquefaction hazard. The findings presented in this dissertation thus form the basis for future development of a further-improved framework.

published_or_final_version / Earth Sciences / Doctoral / Doctor of Philosophy

The characterization of silty soils is usually designated by the percentage of silt contained within the soil matrix, along with the soil’s void ratio, which is used to describe the soil’s current state. The use of these parameters to assess a soil’s strength and undrained behavior is limited when finer material is contained within the soil. Therefore, additional parameters must be considered in order to correctly assess the strength and liquefaction potential of silty soils. These additional parameters include the skeleton void ratio, equivalent void ratio and granulometric factors. The current research investigates the influence of granulometric parameters, specifically the Median Grain Size Ratio (D50/d50), denoted as μDR (or MDR within graphs and charts), on the strength and liquefaction potential of loose silty sands. A series of undrained monotonic triaxial compression tests (σ3’= 69, 83, and 103 kPa) are performed on reconstituted soil samples, using three different base sand samples and a constant silt material. As a result, three distinct median grain size ratios (μDR = 4.2, 6.75, and 9) were tested with fines content ranging from 0-30% for each μDR. The undrained shear strength at all confining pressures tends to increase with in μDR; beyond 10% fines content there was no noticeable influence of μDR. At any μDR the excess PWP is higher than that of clean sand, when fines content is larger than 5% fines content. The slope of the instability line and phase transformation line are directly affected by the μDR and fines content, with an increase in the instability line and decrease in the phase transformation line with a growing μDR. The results indicate loose granular fills can be designed to be stronger and more resilient under extreme conditions by careful choice of materials in which the μDR>6.75 and the fines content does not exceed 10%. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2016. / FAU Electronic Theses and Dissertations Collection

The cyclic resistance of predominantly fine-grained soils has received considerable attention following ground and foundation failures at sites underlain by silt-rich soils during recent earthquakes. In several cases substantial ground deformation and reduced bearing capacity of silt soils has been attributed to excess pore pressure generation during cyclic loading. These field case studies are significant due to the occurrence of liquefaction related phenomena in soils that would be characterized as not susceptible to liquefaction using current geotechnical screening criteria. The most widely used of these criteria, the "Chinese Criteria" and its derivatives, are based solely on soil composition and they are essentially diagnostic tools that categorize the soil in a binary fashion as either liquefiable or non-liquefiable. The most significant limitations of these screening tools are that they fail to account for the characteristics of the cyclic loading. This investigation was undertaken to elucidate the potential for strain development in silts during cyclic loading, and to develop a practice-oriented procedure for evaluating the seismic performance of silts as a function of material properties, in situ stresses, and the characteristics of the cyclic loading. This dissertation presents the results of a multi-faceted investigation of the potential for seismically induced pore pressures and large strain development in silt soils. The primary focus of the research was on the synthesis of laboratory testing results on fine grained soils. Laboratory data from cyclic tests performed at Oregon State University and other universities formed the basis for enhanced screening criteria for potentially liquefiable silts. This data was supplemented with field data from sites at which excess pore pressure generation, liquefaction, and/or ground failures were observed during recent earthquakes. This investigation specifically addressed the behavior of silts during loading in cyclic triaxial tests due to the relative abundance of data obtained for this test. The data was used in conjunction with standard geotechnical index tests to enhance an existing energy based procedure for estimating excess pore pressure generation in silts. This pore pressure model can be used with the uncoupled, stress-based methods for estimating the post-cyclic loading volumetric strain developed in this investigation. The energy-based excess pore pressure model and empirical volumetric strain relationship were used to calibrate for applications involving silt soils a nonlinear, effective stress model for dynamic soil response (SUMDES). The SUMDES model was employed, along with the equivalent linear total stress model SHAKE, to estimate excess pore pressures generated at un-instrumented field sites that have exhibited evidence of liquefaction during recent earthquakes. A comparison of the SUMDES and SHAKE results highlighted the limitations of the latter model for simulating dynamic soil response at various levels of shaking and pore pressure response. The results of the SUMDES modeling at several well documented case study sites are presented in this dissertation. These comparisons are valuable for demonstrating the uncertainties associated with modeling of the effective stress behavior of silt during seismic loading. / Graduation date: 2005