Thesis (M.U.D.)--University of Hong Kong, 1992. / Includes bibliographical references (leaves 261-264) Also available in print.

Thesis (Ph. D.)--University of Idaho, 2006. / Abstract. "June 2006." "In liquefaction, the movement of particles is generally viewed as random and isotropic. A numerical study has been performed based on the hypothesis that as liquefaction occurs, initially randomly placed particles become organized into a lattice structure. As a result, the initial behavior may be isotropic, but there is a progressive movement to anisotropic behavior as cyclic shearing is applied. The study is performed under ideal conditions considering spherically shaped particles of the same size in pure shear. The results of the study showed that the particles organize to the same lattice structure regardless of friction coefficient or shear plane selection. Consequently, this study provides a tool for calibrating constitutive models related to liquefaction."--p. iii. Includes bibliographical references (leaves 45-51). Also available online in PDF format.

Thesis (Ph. D.)--Brigham Young University. Dept. of Civil and Environmental Engineering, 2006. / Includes bibliographical references (p. 263-270).

abstract: The effect of earthquake-induced liquefaction on the local void ratio distribution of cohesionless soil is evaluated using x-ray computed tomography (CT) and an advanced image processing software package. Intact, relatively undisturbed specimens of cohesionless soil were recovered before and after liquefaction by freezing and coring soil deposits created by pluviation and by sedimentation through water. Pluviated soil deposits were liquefied in the small geotechnical centrifuge at the University of California at Davis shared-use National Science Foundation (NSF)-supported Network for Earthquake Engineering Simulation (NEES) facility. A soil deposit created by sedimentation through water was liquefied on a small shake table in the Arizona State University geotechnical laboratory. Initial centrifuge tests employed Ottawa 20-30 sand but this material proved to be too coarse to liquefy in the centrifuge. Therefore, subsequent centrifuge tests employed Ottawa F60 sand. The shake table test employed Ottawa 20-30 sand. Recovered cores were stabilized by impregnation with optical grade epoxy and sent to the University of Texas at Austin NSF-supported facility at the University of Texas at Austin for high-resolution CT scanning of geologic media. The local void ratio distribution of a CT-scanned core of Ottawa 20-30 sand evaluated using Avizo® Fire, a commercially available advanced program for image analysis, was compared to the local void ratio distribution established on the same core by analysis of optical images to demonstrate that analysis of the CT scans gave similar results to optical methods. CT scans were subsequently conducted on liquefied and not-liquefied specimens of Ottawa 20-30 sand and Ottawa F60 sand. The resolution of F60 specimens was inadequate to establish the local void ratio distribution. Results of the analysis of the Ottawa 20-30 specimens recovered from the model built for the shake table test showed that liquefaction can substantially influence the variability in local void ratio, increasing the degree of non-homogeneity in the specimen. / Dissertation/Thesis / M.S. Civil and Environmental Engineering 2013

Liquefaction is a phenomenon in which soil loses a large percentage of its shear resistance due to increased pore water pressure and flows like a liquid. Undrained cyclic loading conditions during earthquakes cause liquefaction of soils, which can lead to catastrophic failures such as bearing capacity failures, slope failures and lateral spreads. The concepts and mechanisms of liquefaction were studied extensively by many researchers. Though the factors affecting the liquefaction response of soils during earthquakes are well documented in literature, there are still some gray areas in understanding the individual and combined effects of factors like frequency, gradation, fines content and surcharge pressure on the initiation of liquefaction. The objective of this thesis is to study the influence of ground motion, soil and site parameters on the initiation of liquefaction in saturated sand beds through laboratory shaking table model tests and numerical studies. Shaking table tests are carried out using a uniaxial shaking table on sand beds of 600 mm thickness. The initiation of liquefaction was observed and identified by measuring the pore water pressure developed during the sinusoidal cyclic loading. Free field liquefaction studies are carried out on sand beds to study the influence of ground motion parameters, namely, input acceleration and frequency of shaking on liquefaction. These studies revealed that acceleration is one of the important parameters that can affect the initiation of liquefaction in sands. Increase in acceleration reduces the liquefaction resistance of sand and a small increase in acceleration can trigger liquefaction. Frequency of shaking did not affect the initiation of liquefaction at lower frequencies but a threshold frequency which triggered instant increase in the excess pore pressures is observed. Liquefaction caused slight initial amplification followed by de-amplification of accelerations due to the stiffness reduction in soils during liquefaction, the effect being more pronounced in the top layers of the sand bed. Pore water pressure ratios during dynamic loading decreased with depth below the surface of the sand bed due to the low initial effective vertical stress and upward transmission of pore pressure during undrained loading. Shaking table tests are carried out to study the influence of soil parameters such as relative density, thickness of dry overlying sand layer and gradation. Relative density of sand can influence the liquefaction potential of sand to a great extent, about 10% increase in relative density bringing down the probability of liquefaction by about 50%. With the increase in height of dry overlying sand layer, liquefaction potential has decreased nonlinearly. Change in grain size altered the pattern of liquefaction and pore pressure development and it is observed that the liquefaction in finer sands is influenced by the frequency of shaking to a larger extent. Surcharge pressure from building loads increased the liquefaction potential and heavier structures got liquefied at lower pore water pressure ratios. Significant post-liquefaction de-amplification was observed in sand beds with surcharge pressure. Parametric numerical analyses are carried out using finite difference program FLAC (Fast Lagrangian Analysis of Continua) with FINN model to measure pore water pressures in the sand bed. Results from numerical analyses with change in the acceleration, surcharge pressure and thickness of dry overlying layer agreed well with the experimental results. However, effect of frequency in numerical studies did not match with the experimental observations, because of the inherent boundary effects in the experimental models. Results from this thesis provided important insights into the development of pore water pressures in sand beds during cyclic loading events, apart from enhancing the understanding towards the effect of various ground motion, site and soil parameters on the initiation of liquefaction in sand beds.

The major objective of this research was to advance the state of the art in interpretation and application of results from in-situ testing of soil, in particular the Cone Penetration Test (CPT), the Self-boring Pressuremeter Test (SBPMT) and the Flat Plate Dilatometer Test (DMT). This study critically examines the equipment, field procedures and methods of test interpretation so that improvements can be made in their application to field liquefaction assessment. Improvements to in-situ test equipment and procedures are proposed. Improvements for the interpretation of CPT data in sands for evaluating relative density, friction angle and modulus are made. A method for prediction of deformation characteristics of clay from CPT data is proposed by incorporating the influence of soil stiffness. A correlation between cyclic stress ratio to cause liquefaction (10 percent double amplitude shear strain) and cone penetration resistance is proposed for sands and silty sands. The proposed CPT liquefaction correlation is substantiated using data from B.C., Japan, China and U.S.A. and appears to represent a good lower bound. The addition of continuous pore pressure measurements during cone penetration is shown to significantly improve the interpretation of the CPT. Data is also presented that clarifies the correlation between the Standard Penetration Test (SPT) and the CPT. Improvements are suggested for the interpretation of SBPMT data in sands for friction angle and modulus. These improvements are applied to the assessment of liquefaction resistance using the SBPMT. New correlations are proposed for estimating the relative density and liquefaction resistance of sand using the results from DMT. A field and laboratory study is carried out to evaluate existing and proposed methods of interpretation of in-situ tests and their application to the assessment of liquefaction resistance. In general the proposed new correlations produce good results, although further field verification is required. / Applied Science, Faculty of / Civil Engineering, Department of / Graduate

This study set out to examine the effectiveness and reliability of six modifications to the Zhang et al. (2004) CPT-based lateral spread model. A regression analysis, distribution charts, and a discriminant analysis are performed to determine how effective the modifications are on the model. From the comparisons and statistical analysis performed in this study, application of these modifications reduces over-predictions from strain-based prediction methods. Unfortunately, the tendency to under-predict displacements on average is also increased.

Eight alcohols in their supercritical states were used individually to treat crude bio-oil and pine wood chips. All supercritical alcohols studied, with the exception of tertbutanol, exhibited the ability to decrease the oxygen content, acid value and/or remove unstable compounds from the crude bio-oil. For supercritical 1-butanol, its use for upgrading of crude bio-oil resulted in a product with much lower oxygen content, lower acid value and fewer unstable compounds. Two CoMo catalysts were examined for their impact on the bio-oil upgrading process with supercritical alcohol. Their influence on the oxygen content, acid value and concentrations of unstable compounds in the processed bio-oil was examined. The basic CoMo/MgO catalyst was demonstrated to effectively eliminate acid content from the bio-oil, regardless of the alcohol employed. Compared with crude bio-oil produced by fast pyrolysis of pine wood lumber, the liquid products produced from supercritical alcohol treatment of pine wood chips possessed one or more of the desirable characteristics: lower acid value, lower oxygen content and fewer unstable compounds. Generally, supercritical butanol isomers produced liquid fuels with lower oxygen content. However, the bulky structure of branched alcohol isomers (secondary and tertiary alcohols) appeared to hinder the degradation of pine wood chips. The CoMo/MgO catalyst exhibited the ability to decrease the acid value, but not to decrease the oxygen content in the liquid product. Wood chip size, wood chip/methanol mass ratios, temperatures, pressures and reaction time were examined in this work. However, the influence of these variables on liquid yield from supercritical methanol treatment of pine wood chips was not substantial.

Note:

It has been found that naturally hydrophobic carbonaceous materials such as coal and graphite can be selectively coagulated and separated from hydrophilic impurities without the use of oily agglomerants, flocculants or electrolytes. The coagulation occurs at ζ-potentials significantly higher than those predicted by the classical DLVO theory, suggesting that it is driven by a hydrophobic interaction energy. Thus, the process is referred to as the selective hydrophobic coagulation (SHe) process. The fundamental development of this process is the focus of this study. In this study, the energy barriers for the coagulation of two different coal samples and a graphite sample have been calculated using the extended DLVO theory, which incorporates the hydrophobic interaction energy in addition to the dispersion and the electrostatic energies. Stability diagrams have been developed from the data, which show that the maximum ζ-potential at which a given coal can coagulate decreases as surface hydrophobicity decreases. For the coagulation of minerals present in coal, the classical DLVO theory has been used for the energy barrier calculations. The results of these calculations provide an excellent correlation with the results from a series of SHC tests conducted with run-of-mine coal. The strength of the coal aggregates have also been investigated by measuring the coagula size distributions under different hydrodynamic conditions. The coagula size distributions were measured using an in-situ particle size analyzer. These results have been used along with models for coagulation rate and breakage rate to determine strength characteristics of the aggregates and to verify the primary parameters controlling the aggregate size. The study found that the coal and graphite aggregates incurred a substantial reduction in size when a small amount of mechanical agitation was applied. Based on this outcome, quiescent continuous processes have been successfully designed and developed to separate the coagulated hydrophobic particles from the dispersed hydrophilic particles. / Ph. D.