Prefabricated vertical drains represent a soil improvement technique that achieves liquefaction mitigation by decreasing the drainage path length and hence expediting the dissipation of excess pore pressures. When evaluating the required spacing between vertical drains to achieve the desired reduction in pore pressure response, simplified design charts or more sophisticated finite element analyses are used to predict the pore pressure response. These charts and programs have not been evaluated in terms of their accuracy because there exists little data with which to compare the numerical predictions. More recently, the effectiveness of prefabricated vertical drains for liquefaction mitigation has been evaluated via small – scale centrifuge testing performed on untreated soil deposits and on soil deposits treated with vertical drains. In particular, the performance of the soil deposits subjected to sinusoidal motions and actual earthquake recordings was tested. The main goal of this research is to compare the experimental observations of pore pressure response from the centrifuge experiments with the numerical predictions. The comparison focuses on the average excess pore pressure ratio (r_(u,avg)) that was developed in the location of a vertical pore pressure array in both the untreated and drain – treated sides of the models. In parallel, a parametric study is performed for the numerical predictions in order to study the effect of each input parameter that influences the pore pressure prediction, namely the effect of soil properties, ground motion characteristics and drain parameters. The numerical predictions are found to provide reliable predictions of the pore pressure response despite the simplicity of the constitutive model employed. The numerical predictions of r_(u,avg) time – histories are generally in good agreement with the recorded values in the centrifuge experiments. In most of the cases, the numerical model managed to predict the same maximum average excess pore pressure ratio, which is the parameter that is used in drain design. To incorporate any uncertainty on the soil properties or on the characteristics of shaking, the use of a smaller pore pressure threshold for drain design is recommended. / text

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Ethanol production at Lantmännen Agroetanol AB in Norrköping began in December 2000. The objective of this master's thesis is to find and optimize factors affecting the yield of the liquefaction, a part of the upstream process. To measure successfulness of liquefaction it is desired that amount of non-solubilized starch is quantified, and hence a method for determination of non-solubilized starch in mash has to be developed. Starch is a carbon reserve in plants. Starch granules are polymers of amylose and amylopectin which are polysaccharides of glucose. When a starch/water solution is heated the starch granules start to absorb water and swell, a process termed gelatinization. The swelling makes the granules susceptible to hydrolysis by enzymes such as alpha-amylase, this is called liquefaction. Eventually the granular structure is broken and the slurry contains solubilized starch which can be saccharified to glucose by glucoamylase. In the bioethanol production process, the milled grain is mixed with water and enzymes. The slurry is heated, gelatinization and liquefaction occurs. Saccharification occurs simultaneously to fermentation. Ethanol is purified from the fermented mash during downstream processing. Starch in the form of starch granules cannot be quantified. The adopted principle for determination of non-solubilized starch in liquefied mash is to wash away the solubilized starch, then quantitatively hydrolyze non-solubilized starch to glucose and quantify glucose. To find and optimize factors significant for yield of liquefaction multiple factor experiments were conducted where eight factors were studied. pH, temperature in mixtank and temperature in liquefaction tank 1 were the most significant factors. The temperature in liquefaction tank 1 should be kept as is is at 74°C. A small rise in pH should shorten the mean length of dextrins which is preferable. An increase of pH from 5.2 to 5.4 is therefore proposed. The temperature in mixtank should also be increased by a few degrees. The yield of the process should be carefully evaluated during the modifications. / Etanolproduktionen på Lantmännen Agroetanol AB i Norrköping började i December 2000. Målet med examensarbetet är att hitta och optimera faktorer som påverkar utbytet av likvifieringen i etanolproduktionen. För att studera utfallet av likvifieringen är det önskvärt att mäta hur mycket stärkelse som inte har löst sig, och därför måste en metod för att mäta olöst stärkelse i mäsk utvecklas. Stärkelse utgör en kolreserv i växter. Stärkelsegranuler är polymerer av amylos och amylopektin, vilka i sin tur är polysackarider av glukos. När en stärkelse/vatten-blandning värms upp börjar stärkelsegranulerna att absorbera vatten och svälla, en process som kallas gelatinisering. Svällningen gör granulerna känsliga mot hydrolys av till exempel enzymet alfa-amylas, vilket kallas för likvifiering. Efter tillräckligt mycket gelatinisering och likvifiering förstörs hela den granulära strukturen och stärkelsen övergår till löst form. Löst stärkelse kan försockras till glukos med enzymet glukoamylas. I produktionen av bioetanol blandas malet spannmål med vatten och enzymer. Slurryn värms upp och gelatinisering och likvifiering sker. Försockring sker simultant med fermenteringen. Etanol renas fram från den fermenterade mäsken i nedströmsprocessen. Stärkelse i granulform kan inte kvantifieras. Den valda metoden för mätning av olöst stärkelse i likvifierad mäsk innebär att den lösta stärkelsen tvättas bort, sedan hydrolyseras den olösta stärkelsen kvantitativt till glukos, vilken kan kvantifieras. Flerfaktorförsök gjordes för att hitta och optimera faktorer signifikanta för utbytet av likvifiering. Åtta olika faktorer studerades. pH, temperatur i mixtank och temperatur i likvifieringstank 1 visade sig vara de tre mest signifikanta faktorerna. Temperaturen i likvifieringstank 1 ska bibehålla samma temperatur som idag, 74°C. En liten höjning av pH borde förkorta medellängden av dextrinerna, vilket är fördelaktigt. En ökning av pH från 5,2 till 5,4 är föreslås därför. Temperaturen i mixtanken ska ökas några få grader. Utbytet av processen måste noggrant utvärderas under modifieringarna.

The collapse of buildings and infrastructure is an unfortunate consequence of major earthquakes (e.g., the 1964 Alaskan earthquake, the 1995 Kobe earthquake in Japan and the 2007 Pisco earthquake in Peru). Liquefaction-induced lateral spreading is known to be one cause of severe damage to deep foundation systems. However, the dynamic soil-structure interaction between liquefied soil and piles is extremely complex and further work is required to define the appropriate design pressures and to understand the mechanisms at work. This thesis presents the findings of an experimental program carried out using the large geotechnical centrifuge at C-CORE in St John’s Newfoundland, to investigate the mechanism of lateral spreading and its implications for dynamic soil-pile interaction. Soil and pile responses were measured using accelerometers, pore pressure transducers, and digital imaging using a high speed camera. Using these images, transient profiles of slope deformation were quantitatively measured using Particle Image Velocimetry (PIV). These tests illustrate the potential for earthquake shaking to excite the natural frequency of the liquefied soil column, which can lead to increased transient lateral pressures on piles in liquefiable ground. This study recommends that this potential for “auto tuning” should be anticipated in design and proposes a new limiting pseudo-static backbone p-y curve for use in the design of piles subjected to lateral spreading ground deformation. / Thesis (Master, Civil Engineering) -- Queen's University, 2009-01-27 10:09:43.902

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Coastal and river environments are exposed to a number of natural hazards that have the potential to negatively affect both human and natural environments. The purpose of this research is to explain that significant vulnerabilities to seismic hazards exist within coastal and river environments and that coasts and rivers, past and present, have played as significant a role as seismic, engineering or socio-economic factors in determining the impacts and recovery patterns of a city following a seismic hazard event. An interdisciplinary approach was used to investigate the vulnerability of coastal and river areas in the city of Christchurch, New Zealand, following the Canterbury Earthquake Sequence, which began on the 4th of September 2010. This information was used to identify the characteristics of coasts and rivers that make them more susceptible to earthquake induced hazards including liquefaction, lateral spreading, flooding, landslides and rock falls. The findings of this research are applicable to similar coastal and river environments elsewhere in the world where seismic hazards are also of significant concern. An interdisciplinary approach was used to document and analyse the coastal and river related effects of the Canterbury earthquake sequence on Christchurch city in order to derive transferable lessons that can be used to design less vulnerable urban communities and help to predict seismic vulnerabilities in other New Zealand and international urban coastal and river environments for the future. Methods used to document past and present features and earthquake impacts on coasts and rivers in Christchurch included using maps derived from Geographical Information Systems (GIS), photographs, analysis of interviews from coastal, river and engineering experts, and analysis of secondary data on seismicity, liquefaction potential, geology, and planning statutes. The Canterbury earthquake sequence had a significant effect on Christchurch, particularly around rivers and the coast. This was due to the susceptibility of rivers to lateral spreading and the susceptibility of the eastern Christchurch and estuarine environments to liquefaction. The collapse of river banks and the extensive cracking, tilting and subsidence that accompanied liquefaction, lateral spreading and rock falls caused damage to homes, roads, bridges and lifelines. This consequently blocked transportation routes, interrupted electricity and water lines, and damaged structures built in their path. This study found that there are a number of physical features of coastal and river environments from the past and the present that have induced vulnerabilities to earthquake hazards. The types of sediments found beneath eastern Christchurch are unconsolidated fine sands, silts, peats and gravels. Together with the high water tables located beneath the city, these deposits made the area particularly susceptible to liquefaction and liquefaction-induced lateral spreading, when an earthquake of sufficient size shook the ground. It was both past and present coastal and river processes that deposited the types of sediments that are easily liquefied during an earthquake. Eastern Christchurch was once a coastal and marine environment 6000 years ago when the shoreline reached about 6 km inland of its present day location, which deposited fine sand and silts over this area. The region was also exposed to large braided rivers and smaller spring fed rivers, both of which have laid down further fine sediments over the following thousands of years. A significant finding of this study is the recognition that the Canterbury earthquake sequence has exacerbated existing coastal and river hazards and that assessments and monitoring of these changes will be an important component of Christchurch’s future resilience to natural hazards. In addition, patterns of recovery following the Canterbury earthquakes are highlighted to show that coasts and rivers are again vulnerable to earthquakes through their ability to recovery. This city’s capacity to incorporate resilience into the recovery efforts is also highlighted in this study. Coastal and river areas have underlying physical characteristics that make them increasingly vulnerable to the effects of earthquake hazards, which have not typically been perceived as a ‘coastal’ or ‘river’ hazard. These findings enhance scientific and management understanding of the effects that earthquakes can have on coastal and river environments, an area of research that has had modest consideration to date. This understanding is important from a coastal and river hazard management perspective as concerns for increased human development around coastlines and river margins, with a high seismic risk, continue to grow.

Soil liquefaction has caused major damage to pile foundations in many previous earthquakes. Pile foundations are relatively vulnerable to lateral loads such as those from earthquake shaking; during liquefaction this vulnerability is particularly pronounced due to a loss of strength and stiffness in the liquefied soil. In this research seismic assessment methods for piles in liquefied soil are studied; a simplified approach and a detailed dynamic analysis are applied to a case study of a bridge founded on pile foundations in liquefiable soils. The likely effects of liquefaction, lateral spreading and soil-structure interaction on the bridge during a predicted future earthquake are examined. In the simplified approach, a pseudo-static beam-spring method is used; this analysis can be performed using common site investigation data such as SPT blow count, yet it captures the basic mechanism of pile behaviour. However, the phenomenon of soil liquefaction is complex and predictions of the seismic response are subject to a high level of aleatoric uncertainty. Therefore in the simplified analysis the key input parameters are varied parametrically to identify key features of the response. The effects of varying key parameters are evaluated and summarised to provide guidance to designers on the choice of these parameters. The advanced analysis was based on the effective stress principle and used an advanced constitutive model for soil based on a state concept interpretation of sand behaviour. The analysis results give detailed information on the free field ground response, soil-structure interaction and pile performance. The modelling technique is described in detail to provide guidance on the practical application of the effective stress methodology and to illustrate its advantages and disadvantages when compared to simplified analysis. Finally, a two-layer finite element modelling technique was developed to overcome the limitations conventional two-dimensional (2-D) models have when modelling three-dimensional (3-D) effects. The technique, where two 2-D finite element meshes are overlapped and linked by appropriate boundary conditions, was successful in modelling 3-D characteristics of both deep-soil-mixing walls for liquefaction remediation and pile groups in laterally spreading soil. In both cases the new two-layer model was able to model features of the response that conventional one-layer models cannot; for cases where such aspects are important to the overall response of the foundation, this method is an alternative to the exhaustive demands of full 3-D analysis.