Liquefaction of soil is one of the major contributing factors for damages of infrastructures and utility services during earthquake. Liquefaction occurs when short strong shaking creates undrained loading condition in saturated soil deposit thereby increases pore water pressure, which eventually equals the effective confining pressure resulting in significant reduction in shear strength and bearing capacity of soil deposit. Several studies have been conducted to investigate the effect of polypropylene fiber on sand deposit as a measure to prevent liquefaction but most of them are based on static tests. Therefore, the present study, tries to understand liquefaction characteristics of sand reinforced with polypropylene fiber based on cyclic triaxial test. The main objectives of this study are (i) to explore the effect of polypropylene fiber on pore pressure generation and deformation characteristics of sand, and (ii) to observe the effect of confining pressure on liquefaction characteristics of sand-fiber mixture. A series of stress controlled cyclic triaxial tests were performed at 5 and 10 psi effective confining pressures. At 5 psi effective confining pressure, specimens of clean sand, and sand containing 0.05, 0.075, 0.1, and 0.3% polypropylene fiber by dry weight were tested at 0.2, 0.25, 0.3, and 0.4 Cyclic Stress Ratio (CSR). However, at 10 psi effective confining pressure, specimens were also tested for 0.5%, and 0.75% fiber in addition to those at 5 psi confining pressure at 0.2, 0.3, and 0.4 CSR. Based on the test results, it was observed that, cyclic shear stress increases with the increase in initial effective confining pressure. Also, for a given CSR, liquefaction resistance decreased with the increase in effective confining pressure. Furthermore, significant improvement in liquefaction resistance was observed when the fiber content exceeded beyond 0.075% at 5 psi confining stress. However, at 10 psi confining pressure, addition of fiber did not help in improvement of liquefaction resistance of sand except when cyclic shear stress was applied at 0.2 CSR. At 0.2 CSR, although the specimens did liquefy based on pore pressure generation criteria at all fiber contents, specimens containing 0.5% and 0.75% fiber did not ever reach 2.5% and 5% DA (Double Amplitude) deformation throughout 1000 loading cycles.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1980. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE. / Bibliography: leaves 294-308. / by Howard D. Franklin. / Ph.D.

Earthquakes have been historically perceived as one of the most damaging natural hazards. Seismic soil liquefaction is often one of the major sources of damage and disruptions, and has been observed to severely affect key lifelines. Settlement and tilting of shallow foundations resting on saturated sandy/silty soils has been repeatedly observed throughout the world as a consequence of liquefaction or softening of the foundation soil. Such settlements and tilts can render structures unusable, and homes uninhabitable, causing significant economic losses. Despite the undoubted relevance of this phenomenon, field data on the liquefaction induced settlement of shallow foundations are scarce. New data from 24 buildings that suffered settlement and tilting as a consequences of soil liquefaction during the February 27th 2010 Maule earthquake in Chile, are presented in this work to supplement the existing field cases database. Due to the complexity of this phenomenon, field data are not suffcient to fully understand the mechanisms controlling the settlement of structures resting on liquefied or softened ground.In this framework, centrifuge modelling provides a valuable tool for research by reproducing field conditions in a controlled environment. A series of 10 dynamic centrifuge tests were performed as part of this work. Thanks to the University of Dundee newly installed centrifuge-mounted servohydraulic earthquake simulator, scaled version of field earthquake motions were reproduced in the models tested, enhancing the reliability of experimental results. Particular attention was given to the effect of key parameters on the observed foundation settlement. These parameters are the bearing pressure of the foundation, the thickness of the liquefied soil layer and the soil's relative density. The effect of the soil layering pattern was also investigated, with particular attention to the effect of a low permeability soil crust overlying the liquefied soil. Results suggest that the excess pore pressure generation in the foundation soil is significantly influenced by the stress distribution due to the presence of the foundation itself. In particular, lower excess pore pressure where measured in soil subjected to high static shear stresses (i.e. below the edge of a footing). The soil stratification pattern, and the relative thicknesses of the liquefied and un-liquefied portions of the soil profile, were also found to play a crucial role in determining the seismic demand at foundation level and the type of failure mechanism leading to foundation settlement. Observed differences between centrifuge (i.e. field) and element testing soil response are also discussed. Experimental results are compared to field observations, with the aim of improving the current understanding of the behaviour of structures built on shallow foundations in the eventuality of seismic induced liquefaction of their foundation soil.

A thesis submitted to the Faculty of Engineering, University of the Witwatersrand, in fulfilment of the requirements of the degree of Doctor of Philosophy in Engineering / The thesis describes the determination of the steady state line for the Merriespruit gold and Bafokeng platinum tailings by means of triaxial undrained compression tests. It shows that there are numerous steady state lines for the above mentioned tailings products and thatthe location oftheirsteady state lines in void ratio- mean confining effective stress space is influenced by the percentage fines (particles smaller than 0.075mm) present in the tailings, among other factors. As the percentage fines increases so the steady state line for the particular material shifts downwards in void ratio- mean confining effective stress space. The difficulty of defining a unique steady state line for a particular fines content tailings, due to errors in measurement of initial size, mass, etc. and changes in void ratio due to flooding, saturation and consolidation of the moist tamped triaxial test samples is illustrated and it is recommended that error bands be assigned to the steady state lines. The steady state lines determined for the Merriespruit gold tailings and the concepts of liquefaction are combined with evidence obtained from the post failure investigation into the Merriespruit flow slide failure to prove the premise that the flow slide was as a result of static liquefaction failure of the tailings. It is also illustrated that the notion of using a single steady state line to evaluate the liquefaction susceptibility of a tailings dam is insufficient due to the particle size distribution of the tailings varying along the beach length of the tailings dam and the location of the steady state line being influenced by the percentage fines content. Flume modelling using the Merriespruit gold tailings were carried to obtain a qualitative understanding of the behaviour of flow slides. Comparisons between the flume model tests and the Merriespruit flow slide (prototype) showed that it is difficult to obtain a correlation between the two due to the influence of scale, different dominating forces in the model and prototype and the inherent variability associated with such geotechnical phenomena- particularly in the preparation and deposition of the tailings in the flume model. Keywords: liquefaction, steady state line, flow slide, failure, flume modelling, Merriespruit, Bafokeng, gold, platinum, tailings / AC 2018

Over the past several decades, empirical formulas have been developed and improved to predict liquefaction and lateral spread based on a database of case histories from observed earthquakes, such as Youd et al. (2002) and Rauch and Martin (2000). The 2010 Maule Chile earthquake is unique first of all because it is recent and was not used to develop recent liquefaction and lateral spread evaluation methods, and therefore can be reasonably used to evaluate the effectiveness of such equations. Additionally, the 8.8 magnitude megathrust event fills a significant gap in the databases used to develop these empirical formulas, which tends to under represent large magnitude earthquakes and events which occur along subduction zones. Use of case histories from this event will therefore effectively test the robustness and accuracy of these methods.As a part of this comparison, data will be collected from two piers in Port Coronel, Chile: Lo Rojas or Fisherman's Pier, and el Carbonero. Lo Rojas is a municipally owned pier which failed in the 2010 earthquake. Dr. Kyle Rollins gathered detailed engineering survey data defining lateral spread displacements along this pier in a reconnaissance visit with other GEER investigators after the earthquake. El Carbonero was under construction during the earthquake, but no known lateral displacements were observed. Collaboration with local universities and personnel contributed a great deal of knowledge about the soil profile. In early April 2014, collection of SPT and CPT data began in strategic locations to fill gaps of understanding about the stratigraphy near the two piers. Additional testing will provide necessary information to carry out predictions of displacements using current empirical models, which can then be compared with observed displacements collected after the earthquake. Collected data will also be complied, and this alone will provide useful information as it represents a unique case history for future evaluation.The goals of this study are therefore: (1) Collect data for two piers (Lo Rojas and el Carbonero) in Port Coronel, Chile to provide a useful case history of lateral displacements observed; (2) Conduct a liquefaction and lateral spread analysis to predict displacement of the two piers in question, considering lateral spread and slope stability; (3) Compare predicted values with observed displacements and draw conclusions on the predictive capabilities of analyzed empirical equations for similar earthquakes (4) Make recommendations to improve when possible.

Improving seismic hazard analysis is an important part of building safer structures and protecting lives. Since large magnitude earthquakes are rarer than other earthquakes, it is harder to model seismic hazards such as lateral spread displacements for these events. Engineers are often required to extrapolate current lateral spreading models when designing utilities, bridges, and piers to withstand the ground displacements caused by earthquakes with magnitudes larger than 8.0. This study uses three case histories from the Maule Chile 2010 earthquake (Mw =8.8) to develop recommendations on which models are most accurate for large earthquake events and how to improve the accuracy of the models. Six empirical models commonly used in engineering practice are compared. The model that best matches the Maule Chile case histories uses local attenuation relationships to make it easier to apply the model to any seismic region. Models that use lab data from cyclic shear tests over predict displacements but using a strain-reduction factor with depth significantly improved the accuracy of the results. Site-to-source distances can vary greatly between geographic seismic and faulting mechanisms. For this reason, models that depend on an internal source-to-site distance show less promise with large subduction zone earthquakes throughout the world. Models with site-to-source distances are most accurate in the western United States and Japan because the case histories for these models came from those countries.

This thesis presents numerical techniques which have been developed to analyse three dimensional problems in offshore engineering. In particular, the three dimensional liquefaction analysis of offshore foundations on granular soils is the main subject of the thesis. The subject matter is broadly divided into four sections: 1)Development of an efficient method for the three dimensional elasto?plastic finite element analysis of consolidating soil through the use of a discrete Fourier representation of field quantities. 2)Validation of the three dimensional method through analyses of shallow offshore foundations subjected to three dimensional loading and investigation of the yield locus for foundations on purely cohesive soils. 3)Formulation of governing equations suitable for three dimensional liquefaction analyses of offshore foundations founded on granular soil, presentation of a method for liquefaction analyses, and application of the method in modified elastic liquefaction analyses of offshore foundations. 4)Application of a conventional elasto?plastic soil model in the liquefaction analyses of offshore foundations using the three dimensional finite element method. The finite element method developed in this thesis provides a rigorous and efficient numerical tool for the analysis of geotechnical problems subjected to three dimensional loading. The efficiency of the numerical tool makes it possible to tackle some of the problems in geotechnical engineering which would otherwise need enormous computing time and thus would be impractical. The accuracy of the numerical scheme is demonstrated by solving the bearing capacity problem of shallow foundations subjected to three dimensional loading. The generalized governing equations and the numerical method for liquefaction analyses presented in this thesis provide a solid base for the analysis of offshore foundations subjected to cyclic wave loading where they are founded on potentially liquefiable soil. The practicability of the numerical scheme is also demonstrated by a modified elastic liquefaction analysis of offshore foundations. The liquefaction phenomenon is redefined in the context of the conventional Mohr?Coulomb model, so that a relatively simple and practical model for elasto?plastic liquefaction analysis is presented. The three dimensional finite element method together with the numerical scheme for liquefaction analysis and the elasto?plastic soil model provide a suitable practical engineering tool for exploring the responses of offshore foundations subjected to cyclic wave loading.

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

The seismic cone penetration test (SCPTu) is the most efficient means for geotechnical site characterization and the evaluation of seismic ground hazards. In this thesis, software systems including ShearPro, ClusterPro, and InSituData, are developed to automate post processing of these SCPTu data. ShearPro is developed to automate the post-processing of the shear wave signals. ClusterPro uses the proposed three-dimensional cluster analysis approach for soil stratification. InSituData facilitates the post processing of penetration data for seismic ground hazards analysis. A new three-dimensional soil classification chart is also proposed in this thesis to help discern soil layers that may be subject to seismic ground hazards, such as loose liquefied sands and silty sands. These methods are then applied to SCPTu data collected at previously-identifed paleoliquefaction sites located in the New Madrid Seismic Zone (NMSZ). For liquefaction evaluation, the cyclic stress ratio (CSR) is computed using site response analysis by DeepSoil and a measured profile of shear waves derived from the 30-m SCPTU soundings and deep suspension loggings in AR and TN. The natural resistance of the soil to liquefaction, termed the cyclic resistance ratios (CRRs), is evaluated based on both deterministic procedures and probabilistic procedures. Based on liquefaction evaluation results at selected paleoliquefaction sites, regional CRR criteria for liquefaction are developed for the NMSZ. As even the latest major earthquakes in NMSZ occurred nearly 200 years ago, aging effects might be an important factor to consider in utilizing the liquefaction criteria to assess the seismic parameters associated with the previous earthquakes. The aging effects in the NMSZ were investigated through large scale blast-induced liquefaction tests conducted in the NMSZ. Then a procedure to estimate seismic parameters associated with previous earthquakes is proposed. It utilizes both the liquefaction criteria based on SCPTu tests and the empirical attenuation relations developed for the corresponding regions. The approach is validated through data evaluation related to the 1989 Loma Prieta earthquakes in California and then applied to previous historic earthquakes in the NMSZ.

Thesis (M.S.)--Oregon State University, 2002. / Typescript (photocopy). Includes bibliographical references. Also available on the World Wide Web.