The feasibility of using ground improvement at existing highway bridges to mitigate the risk of earthquake-induced liquefaction damage has been studied. The factors and phenomena governing the performance of the improved ground were identified and clarified. Potential analytical methods for predicting the treated ground performance were investigated and tested. Key factors affecting improved ground performance are the type, size, and location of the treated ground. The improved ground behavior is influenced by excess pore water pressure migration, ground motion amplification, inertial force phasing, dynamic component of liquefied soil pressure, presence of a supported structure, and lateral spreading forces. Simplified, uncoupled analytical methods were unable to predict the final performance of an improved ground zone and supported structure, but provided useful insights. Pseudostatic stability and deformation analyses can not successfully predict the final performance because of their inability to adequately account for the transient response. Equivalent-linear dynamic response analyses indicate that significant shear strains, pore water pressures and accelerations will develop in the improved ground when the treated-untreated soil system approaches resonance during shaking. Transient seepage analyses indicate that evaluating pore pressure migration into a three-dimensional improved zone using two-dimensional analyses can underestimate the pore pressures in the zone. More comprehensive, partially-coupled analyses performed using the finite difference computer program FLAC provided better predictions of treated ground performance. These two-dimensional, dynamic analyses based on effective stresses incorporated pore pressure generation, non-linear stress-strain behavior, strength reduction, and groundwater flow. Permanent movements of structures and improved soil zones were predicted within a factor of approximately two. Predictions of ground accelerations and pore water pressures were less accurate. Dynamic analyses were performed with FLAC for an example bridge pier and stub abutment on an approach embankment supported on shallow foundations and underlain by thick, liquefiable soils with and without improved ground zones. Ground improvement that restricted movements of the pier and stub abutment to tolerable levels included improved zones of limited size extending completely through the underlying liquefiable soils and formed through densification by compaction grouting or cementation by chemical grouting or jet grouting. A buttress fill at the abutment was unsuccessful. / Ph. D.

The current approach for using cone penetration test data to estimate soil behavior during seismic loading involves the comparison of the seismic stresses imparted into a soil mass during an earthquake to the penetration resistance measured during an in-situ test. The approach involves an indirect empirical correlation of soil density and other soil related parameters to the behavior of the soil during the loading and does not involve a direct measurement of the dynamic behavior of the soil in-situ. The objective of this research was to develop an approach for evaluating the in-situ behavior of soil during dynamic loading directly through the use of a vibrating piezocone penetrometer. Cone penetration tests were performed in a large calibration chamber in saturated sand samples prepared at different densities and stress levels. A total of 118 tests were performed as part of the study. The piezocone penetrometer used in the investigation was subjected to a vibratory load during the penetration test. The vibratory units used in the investigations were mounted on top of a 1m section of drill rod that was attached at the lower end to the cone penetrometer. Pneumatic impact, rotary turbine, and counter rotating mass vibrators were used in the investigation. The vibration properties generated by the vibratory unit and imparted into the soil were measured during the penetration test by a series of load cells and accelerometers mounted below the vibrator and above the cone penetrometer, respectively. The tip resistance, sleeve friction and pore water pressure were also measured during the test by load cells and transducers in the cone itself. The vibration and cone data were compiled and compared to evaluate the effect of the vibration on the penetration resistance and pore water pressure in the soil mass. The results of the testing revealed that the influence of the vibration on the penetration resistance value decreased as the density and the mean effective stress in the soil increased, mainly because the pore water pressure was not significantly elevated throughout the entire zone of influence of the cone penetometer at the elevated stress and density conditions. An analysis of the soil response during the testing resulted in the generation of a family of curves that relates the soil response during the vibratory and static penetration to the vertical effective stress and density of the soil. The data used to generate the curves seem to agree with the proposed values estimated through the empirical relationship. An evaluation of the effects of the frequency of vibration was also performed as part of the study. The largest reduction in penetration resistance occurred when the input vibration approximated the natural frequency of the soil deposit, suggesting that resonance conditions existed between the input motion and the soil. An energy-based approach was developed to compare the energy imparted into the soil by the vibrator to the energy capacity of the soil. The input energy introduced into the soil mass prior to the reduction in penetration resistance agrees well with the energy capacity of the soil, especially in tests at the low effective stress level where a high excess pore water pressure was observed. / Ph. D.

This thesis examines the 2018 failure of the Northern Tailings Storage Facility at Cadia Valley Operations, located in New South Wales, Australia. First, the importance of examining and understanding failure mechanisms and post failure kinematics is described. Within which we understand that in the current state of affairs it is exceedingly difficult, or nigh impossible to perform without the use of large strain analyses, which have yet to permeate into the industry to a significant degree. Second, the initial construction and state of the dam just prior to failure is defined, with the materials and their properties laid out and discussed in depth as well as our means of modeling their behavior. Third, we validate and discuss our results of the base model of the dam based on key topographic features from initial and post-failure field measurements. After validation, we examine the influences of each of the different materials on the runout, comparing final topographies of different simulations with the actual final topography observed. This study was a valuable method of validating the Material Point Method as a means of modeling large deformations, as well as demonstrating its powerful applications towards catastrophic disaster prevention. The study validates and provides a greater understanding of the event of the Cadia Tailings Storage Facility Failure, and presents a framework of steps to perform similar examination on future tailings dams as a means of providing risk management in the event of failure. / Master of Science / Tailings dams are structures integral to the life cycle of mining and mineral processing. After mining and the processing of mined materials, the leftover material, known as "tailings" are pumped and stored behind these structures, usually indefinitely. These structures are unique because they are usually expanded as additional storage space for these materials is required. Over the past several decades, the rate at which catastrophic or serious tailings dam failures occur out of failures has been on the rise. Because of this, it becomes necessary to better understand the failure and post-failure movements of the dam. This thesis presents one such failure, the Cadia Tailings Dam Failure of 2018, which is located in New South Wales, Australia. It applies the Material Point Method, a numerical method which allows for largestrain deformations, to examine the post-failure mechanism and interpret various influences by the different materials on the final runout. Because of this, the paper provides insights on the importance of understanding large strain analyses, discussing and presenting the incidents of the failure. The model used for reference is validated using topographic and field data taken after the failure, allowing for a comparison with future models which vary the geometry and material characteristics of the event. A procedural plan is proposed to apply to future analyses, allowing for the analysis to be applied to other events and tailings dam structures, for further insight on influences of variability and material properties on post-failure topography and geometry.

Methods for the preparation of active carbons from many kinds of carbonaceous material have been described in the literature. Many processes of activation for many different raw materials are used to obtain active carbons for specific purposes. In general, all of these processes involve a low temperature carbonization of the raw material followed by a slow, controlled oxidation of the carbonized product. A high temperature of carbonization (above 600°C.) results in a product which is not active and cannot be activated. Any selection of a process or raw material must be based on a knowledge of the ultimate use of the product as well as on economic considerations. Certain physical properties are desirable for certain uses in addition to the general property of being adsorbent to foreign molecules. A gas adsorbent carbon should be dense with a rather small pore size; while liquid adsorbent carbons should be less dense, not triable, easily filterable from solutions, and have a larger pore size than the gas adsorbent type of carbon. In view of the low yield obtained in any process of activation, a cheap and plentiful raw material would be advantageous. Coal is such a raw material and active carbons have been prepared and used to a limited extent from coals. It has been reported that an initial chlorination of a geologically young coal before its carbonization results in a high yield of a good active carbon. The existence of large deposits of such a coal in the Piedmont section of Virginia and North Carolina which has not been exploited to any great extent, because it is not suitable as a fuel, seems to warrant a further investigation of this chlorination process with an idea of its possible economic use in the preparation of an active carbon. The purpose of this investigation in the preparation of a liquid adsorbent active carbon from a high volatile Midlothian coal by a process of chlorination followed by carbonization and steam activation. / M.S.

Liquefaction induced settlement is an earthquake hazard engineers face when developing infrastructure. Current methods for estimating liquefaction induced settlement are done in a free field condition. This assumption is not an accurate way to describe the soil because in most cases the soil will bear some kind of infrastructure. Evaluation of liquefaction induced settlement in a non-free-field condition is a more appropriate way. Using the Bullock et al. CAV model, Bullock et al liquefaction induced settlement model, and probabilistic seismic hazard software from the USGS, a full performance-based procedure for the estimation of liquefaction-induced building settlement in the non-free-field condition was created. To test the validity of the program, various locations, structures, and soil profiles were tested. The output of settlement hazard curves showed results consistent to liquefaction induced settlement trends described in other research. Areas with higher seismicity had higher expected liquefaction induced settlement. Analysis of individual location revealed that soil profile, structure, and foundation all play a role in the estimation of liquefaction induced settlement. Test cases with loose soil predicted higher liquefaction induced settlement than areas with dense soils. Structure and foundation parameters are related through the bearing pressure. These parameters seem to be most influenced by bearing pressure. Test cases with higher bearing pressures showed a higher predicted liquefaction induced settlement than those with smaller bearing pressures.

In recent years supercritical fluid chromatography has gained attention as an alternative technique to high performance liquid chromatography for the analyses of nonvolatile or thermally labile compounds, whose analysis with gas chromatography is impossible. The work presented here demonstrates a system that allows supercritical fluid extraction of the sample with subsequent direct introduction of a fraction of. this extract onto the column for analysis with supercritical fluid chromatography. Such a procedure has several inherent advantages to traditional sampling, where extraction or dissolution of the sample is done in a liquid. A valving scheme is described to accomplish this task and is evaluated for use with several different samples, including fuels and food products, with direct comparisons made between traditional sampling and direct on-line extraction. In most cases, the chromatograms were very similar, however later eluting components were sometimes lower in concentration with this method when compared to traditional sampling techniques. The apparatus was demonstrated in the analysis of high boiling coal derived material. Analysis of this material is accomplished by preliminary class separation with subsequent supercritical fluid extraction and analysis by packed column supercritical fluid chromatography. Detection included variable wavelength UV and FTIR spectrometry. The coal derived products studied were taken from a bench scale coal liquefaction reactor, in which the same catalyst was used for twenty-five consecutive days. The changes that occur as the catalyst decays were determined chromatographically for a portion of the high boiling products. The changes were noted best in the aromatic fraction analysis, where a trend towards molecules with higher numbers of condensed rings was observed as the catalyst decayed. / Master of Science

Soil liquefaction during earthquakes is a phenomenon that can cause tremendous damage to structures such as bridges, roads, buildings, and pipelines. The objective of this research is to develop an energy-based approach for evaluating the potential for liquefaction triggering. The current state-of-practice for the evaluation of liquefaction triggering is the "simplified" stressbased framework where resistance to liquefaction is correlated to an in situ test metric (e.g., normalized standard penetration test N-value, N1,60cs, normalized cone penetration tip resistance, qc1Ncs, or normalized small strain shear wave velocity, Vs1). Although rarely used in practice, the strain-based procedure is commonly cited as an attractive alternative to the stress-based framework because excess pore pressure generation (and, in turn, liquefaction triggering) is more directly related to strains than stresses. However, the method has some inherent and potentially fatal limitations in not being able to appropriately define both the amplitude and duration of the induced loading in a total stress framework. The energy-based method proposed herein builds on the merits of both the stress- and strain-based procedures, while circumventing their inherent limitations. The basis of the proposed energy-based approach is a macro-level, low cycle fatigue theory in which dissipated energy (or work) per unit volume is used as the damage metric. Because dissipated energy is defined by both stress and strain, this energy-based method brings together stress- and strain-based concepts. To develop this approach, a database of liquefaction and nonliquefaction case histories was assembled for multiple in situ test metrics. Dissipated energy per unit volume associated with each case history was estimated and a family of limit-state curves were developed using maximum likelihood regression for different in situ test metrics defining the amount of dissipated energy required to trigger liquefaction. To ensure consistency between these limit-state curves and laboratory data, a series of cyclic tests were performed on samples of sand. These laboratory-based limit-state curves were reconciled with the field-based limit-state curves using a consistent definition of liquefaction. / Doctor of Philosophy / Soil liquefaction during earthquakes is a phenomenon that can cause tremendous damage to structures such as bridges, roads, buildings, and pipelines. The objective of this research is to develop an energy-based approach for evaluating the potential for liquefaction triggering. Current procedures to evaluate liquefaction triggering include stress-based and strain-based procedures. However, these procedures have some inherent and potentially fatal limitations. The energy-based method proposed herein builds on the merits of both the stress- and strain-based procedures, while circumventing their inherent limitations. The proposed energy-based approach uses dissipated energy (or work) per unit volume to evaluate the potential for liquefaction. Because dissipated energy is defined by both stress and strain, this energy-based method brings together stress- and strain-based concepts. To develop this approach, a database of case histories in which liquefaction was either observed or not observed was assembled. Dissipated energy per unit volume associated with each case history was estimated and a family of relationships was regressed to define the amount of dissipated energy required to trigger liquefaction. Results from a series of cyclic laboratory tests performed on samples of sand were reconciled with the field-based relationships using a consistent definition of liquefaction. This research proposes a method that is based on a robust mechanistic framework that will make it easier to evaluate liquefaction for circumstances that are not well represented in current liquefaction evaluation procedures. The components of the proposed energy-based procedure are developed consistently and are presented in such a way that this procedure can be readily adopted by practitioners who are already familiar with existing liquefaction evaluation procedures. The broader impacts of this work will help to minimize losses from earthquakes by improving the way engineers evaluate liquefaction.

The 2010-2011 Canterbury, New Zealand, Earthquake Sequence (CES) resulted in 185 fatalities and approximately $NZ40 billion in damage, much of which was due to liquefaction and related phenomena. As a result, an extensive soil improvement field testing program was initiated and Rammed Aggregate Piers� (RAP) were shown to be a feasible method to mitigate the risk from liquefaction during future events. To better design and more fully assess the efficacy of reinforcement techniques against liquefaction, pre- and post-treatment in-situ test data are compiled, to include results from cone penetration tests (CPT), direct-push crosshole tests, and vibroseis (T-Rex) shaking tests. The data are used to evaluate the capabilities of numerical tools to predict the liquefaction response of unimproved and improved sites. A finite difference (FD) numerical model is developed in a FLAC platform and a coupled analysis using the Finn model with Byrne (1991) formulation is conducted. The FD model calibrated for top-down shakings similar to the vibroseis tests succeeded in qualitatively reproducing the general observed behavior without quantitatively matching the in-situ values for shear strains and excess pore pressure ratios. The introduction of the RAP elements to the FD model reduced the shear strain, but slightly overestimated that reduction. Considering more advanced constitutive models that better simulate the complexity of the soil behavior under dynamic loading would likely increase the accuracy of the predicted response. / MS / During earthquakes, a significant loss of strength in soil can occur. This phenomenon, known as liquefaction, can have a devastating impact on the area affected. The 2010-2011 Canterbury, New Zealand, Earthquake Sequence (CES) resulted in 185 fatalities and approximately $NZ40 billion in damage, much of which was due to liquefaction and related phenomena. Consequently, the New Zealand Earthquake Commission implemented a field testing program in order to investigate the efficiency of ground improvement techniques in reducing soil liquefaction potential. One of the tested techniques was Rammed Aggregate Piers™ (RAP) and was shown to be a feasible method in mitigating the risk from liquefaction during future events. The focus of this study is to develop a numerical model capable of predicting the liquefaction response of unimproved and RAP-improved sites. Pre- and post-treatment test data are therefore compiled and used to calibrate the model. The numerical model calibrated for shakings similar to the on-site tests succeeded in qualitatively, but not quantitatively, reproducing the behavior observed in the field. The introduction of the RAP elements to the model revealed an improvement against liquefaction hazard; however, the improvement was overestimated compared to the field results. Considering more advanced numerical features that better simulate the complexity of the soil behavior under dynamic loading would likely increase the accuracy of the predicted response.

Field-based liquefaction evaluation procedures include the stress-based, strain-based, and energybased based approaches. The existence of a volumetric threshold shear strain, γtv, under which there is no development of excess pore pressures, and the unique relationship between pore pressure ratio and cyclic shear strain, γc, make a compelling argument for using a strain-based approach. However, the cyclic strain approach has not yet been standardized for field evaluations. The primary objective of this thesis is to use published databases of 415 shear-wave velocity and 230 Standard Penetration Test liquefaction field case histories to investigate the performance of the cyclic strain approach for the evaluation of initial liquefaction relative to the cyclic stress approach. Additionally, the concept of the γtv is expressed in terms of the peak ground surface acceleration and defined as the threshold amax. Computing (amax)t could provide a fast and simple evaluation for initial liquefaction, where no liquefaction is expected for a minimum computed (amax)t determined from the case histories. The variant of the strain-based procedure proposed herein avoids the direct need for laboratory cyclic testing by employing pore pressure generation models that are functions of cyclic shear strain, number of equivalent cycles, and relative density to predict initial liquefaction. The results from the proposed procedure are compared with those of the stress-based approach to determine which better matches the field observations of the case histories. It was found that the cyclic strain approach resulted in 70% to 77% correct predictions. In contrast, the cyclic stress approach yielded 87% to 90% correct predictions. The reasons why the predictions were not always correct with the cyclic strain approach are due to inherent limitations of the cyclic strain approach. Most significantly, an inherent and potentially fatal limitation of the strain-based procedure is it ignoring the softening of the soil stiffness due to excess pore pressure in representing the earthquake loading in terms of γc and neqγ. / Master of Science / Earthquakes can cause heavy damage when they occur. One of the ways in which this happens is when the earthquake shaking causes the soil to behave like a liquid. This is the phenomenon known as liquefaction. An example of liquefaction is a person sinking in quicksand. Relating this to earthquakes, liquefaction can be thought of as a building sinking in quicksand that formed as a consequence of earthquake shaking. Destructive cases of liquefaction have been reported in almost all major earthquakes. When cases of liquefaction are properly documented, they can provide information that will help engineers and scientists assess the efficacy of existing liquefaction evaluation procedures and/or to develop new procedures. There are different methods to evaluate the occurrence of liquefaction, with the cyclic stress approach being the most widely used. This study assesses the efficacy of an alternative approach to see if it yields better predictions of liquefaction triggering than the cyclic stress approach. The approach under consideration is called the cyclic strain approach. To examine the effectiveness of the cyclic strain approach, sites that experienced liquefaction in the past were analyzed to see if the predictions made with the approach matched the past field observations. Due to potential shortcomings in implementing the strain based procedure, as well as inherent limitations of the procedure, the strain-based procedure yielded predictions that were inferior to the more widely used stress-based procedure.

The response of an aggregate pier foundation system during seismic loading was investigated. The factors and phenomena governing the performance of the aggregate pier and the improved ground were identified and clarified. The key factors affecting the performance of the aggregate pier include soil density, stiffness modulus, and drainage capacity. The improved ground is influenced by soil stratification, soil properties, pore pressure dissipation, and earthquake time history. Comprehensive numerical modeling using FLAC were performed. The focus of the study in this research was divided into three parts: the studies of the ground acceleration, the excess pore water pressure ratio and the shear stress in soil matrix generated during seismic loading. Two earthquake time histories scaled to different peak acceleration were used in the numerical modeling: the 1989 Loma Prieta earthquake (pga = 0.45g) and the 1988 Saguenay earthquake (pga = 0.05g). The main results of the simulation showed the following effects of aggregate pier on liquefiable soil deposits: 1) The aggregate pier amplifies the peak horizontal acceleration on the ground surface (amax), 2) The aggregate pier reduces the liquefaction potential up to depth where it is installed, 3) Pore pressures are generally lower for soils reinforced with aggregate pier than unreinforced soils except for very strong earthquake, 4) The maximum shear stresses in soil are much smaller for reinforced soils than unreinforced soils. The excess pore water pressure ratio and the shear stress in the soil matrix calculated by FLAC were generally lower than those predicted by available procedures. / Master of Science