Pile foundations that support offshore structures are required to resist not only static loading, but also dynamic loading from waves, wind and earthquakes. The purpose of this study is to gain a better understanding of the behavior of offshore piles under cyclic or dynamic loading using the finite element approach. To achieve this goal, an appropriate constitutive model is required to simulate the behavior of soils and interfaces. The DSC constitutive model is developed for saturated interfaces to study the behavior under severe shear deformation at the soil-pile interface. Monotonic and cyclic simple shear experiments are conducted on Ottawa sand-steel interfaces under drained and undrained conditions using the Cyclic-Multi-Degree-of-Freedom shear device with porewater pressure measurement (CYMDOF-P). The effect of various parameters such as normal stress, surface roughness of steel, type of loading, and the amplitude and frequency of the applied displacement in two-way cyclic loading are investigated. The data from the simple shear tests on saturated interfaces are used to calculate the parameters in the DSC model. The resulting parameters are then used to verify the DSC model by back predicting tests from which parameters are determined and independent tests that are not used in parameters determination. The model predictions, in general, were found to provide a highly satisfactory correlation with the observations. In the context of DSC, the concept of critical disturbance is developed to identify initiation of liquefaction in saturated Ottawa sand-steel interfaces. This method is based on using microstructural changes in material as an indication of liquefaction identification. The finite element method, along with DSC constitutive model, is used to investigate the response of offshore piles to dynamic loading. These include cyclic loading of axially loaded instrumented pile in clay and full-scale laterally loaded pile in sand. The DSC model is used to model the nonlinear behavior of saturated soils and interfaces. A nonlinear dynamic finite element program DSC-DYN2D based on the DSC modeling approach and the theory of nonlinear porous media is used for this purpose. Results from numerical solutions are compared with field measurements. Strong agreement between numerical predictions and field measurements are an indication of the ability to solve challenging soil-structure interaction problems.Based on the results of this research, it can be stated that the finite element-DSC model simulation allows realistic prediction of complex dynamic offshore pile-soil interaction problems, and is capable of characterizing behavior of saturated soils and interfaces involving liquefaction.

No description available.

The Fischer-Tropsch reaction technology is utilised in Sasol’s Coal-to-liquid plant to produce liquid fuels from low grade coal. There are several processes on the Coal-to-liquid plant that generate aqueous streams which contain a high organic load and require treatment. The main contributors to the wastewater are the Phenosolvan plant, producing stripped gas liquor (SGL), and the Synthol plant, producing Fischer-Tropsch reaction water (FTRW). Stripped gas liquor contains water, organic acids, ammonia, and potentially toxic phenols. Fischer-Tropsch reaction water contains volatile fatty acids and alcohol. Stripped gas liquor is therefore nitrogen-rich while FTRW is nitrogen-deficient and requires nutrient supplementation for anaerobic treatment. Therefore co-treatment of the two streams could reduce nitrogen supplementation requirements. This study is part of a larger project to determine the feasibility of anaerobically co-digesting FTRW and SGL. This study has looked at the influence of SGL on the methanogenic activity of FTRW-acclimated sludge and involved the development of a method which allows accurate recording of the methanogenic activity in batch assays. Other studies involving the anaerobic digestion of high phenolic wastewaters showed that the phenol had an inhibitory effect on the specific methanogenic activity of the sludge, which was not acclimated to the phenol. The objective of this work was to test the hypotheses that (1) anaerobic sludge acclimated to FTRW will be inhibited by high molecular weight organics in SGL and (2) FTRW-acclimated sludge will not degrade phenolic compounds in SGL. This information will be used for designing process configurations for simultaneous treatment of the two streams with minimum contamination of the effluent stream. The serum bottle was used as a small batch reactor and the biogas production was monitored as an indication of the state of the reaction. The biogas produced was collected and measured by the downward displacement of a sodium hydroxide solution, which absorbed the carbon dioxide and collected only the methane. A concentration of 1 g COD/ℓ FTRW was chosen as the reference test due to the reproducibility of the replicates within each experiment as well as its reproducibility across different batches of sludge. For the first inhibition test, the test units contained an additional 5% SGL (0.05 g COD/ℓ SGL) and an additional 15% SGL (0.15 g COD/ℓ SGL, i.e. 13% of the total COD load) respectively, added to 1 g COD/ℓ FTRW. The 5% SGL test unit showed no inhibition compared to the reference unit. There was a reduction in the specific methanogenic activity of the 15% SGL test units compared to the reference unit. Since the total COD load was not the same in each unit, it cannot be conclusively stated that the SGL was responsible for the reduction in SMA, but this seems a reasonable possibility in the light of results from the reference test selection experiments which showed higher SMA at higher organic loading rates. For the second inhibition test, the test units contained 85% FTRW (0.85 g COD/ℓ FTRW) and 15% SGL (0.15 g COD/ℓ SGL) to make up a total COD load of 1 g COD/ℓ. There was an increase in the specific methanogenic activity of the test unit compared to the reference unit. There was very little change in the phenol concentration. Therefore, it was concluded the addition of SGL potentially reduced the SMA and that this could be an inhibitory effect, but that any inhibition would be a function of the concentration of potentially inhibitory substances in SGL and that these concentrations vary from batch to batch. However, the degree of SMA reduction is fairly low and would not prevent co-digestion of the two streams at the concentrations tested. It has been shown that FTRW anaerobic digestion can proceed adequately in the presence of SGL. There was some evidence that phenolics were degraded but at a much slower rate than COD. The percentage reduction in SMA due to additional SGL at concentrations and SGL:FTRW ratios tested was between 0 and 51%. Ultimately, this work is a first step in the development of a co-digestion model relating organic loading rate, SGL:FTRW feed ratio to methane recovery and extent of biodegradation of phenol for use in the design and optimization of a co-digestion system. / M.Sc.Eng. University of KwaZulu-Natal, Durban 2014.

No description available.

Phenol formaldehyde (PF) resol resins have long been used widely as wood adhesives due to their excellent bonding performance, water resistance and durability. With the growing concern for fossil fuel depletion and climate change, there is a strong interest in exploring renewable biomass materials as substitutes for petroleum-based feedstock. Bark, rich in phenolic compounds, has demonstrated potential to partially substitute phenol in synthesizing bio-based PF resins. In this study, acid-catalyzed phenol liquefaction and alkaline extraction were used to convert mountain pine beetle (MPB; Dendroctonus ponderosae) infested lodgepole pine (Pinus contorta) barks to phenol substitutes, liquefied bark and bark extractives. Two types of bio-based phenol formaldehyde (PF) resol resins, namely liquefied bark-PF resin and bark extractive-PF resins, were then synthesized and characterized. It was found that acid-catalyzed phenol liquefaction and alkaline extraction were effective conversion methods to obtain phenol substitute with the maximum yield of 85% and 68%, respectively. The bio-based PF resol resins had higher molecular weights, higher polydispersity indices, shorter gel times, and faster curing rates than the lab synthesized control PF resin without the bark components. Based on the lap-shear tests, the bio-based PF resol resins exhibited comparable wet and dry bonding strength to lab PF resin and commercial PF resin. The post-curing thermal stability of the bio-based PF resins was similar to the lab control PF resin. The liquid-state 13C nuclear magnetic resonance (NMR) study revealed significant influences on the resin structures by the inclusion of the bark components. Methylene ether bridges, which were absent in the lab PF resin, were found in the bio-based PF resins. The bark components favored the formation of para-ortho methylene linkages in the bio-based bark extractive-PF resins. The liquefied bark-PF resin showed a higher ratio of para-para/ortho-para methylene link (-CH2-), a higher unsubstituted/substituted hydrogen (-H/-CH2OH) ratio and a higher methylol/methylene (-CH2OH/-CH2-) ratio than the bark extractive-PF resin. Both tannin components of bark alkaline extractives and phenolated barks contributed to the acceleration of the curing rate of the bio-based resins. This research demonstrated the promise of the bio-based PF resins containing either bark alkaline extractives or liquefied barks as environmentally friendly alternatives to PF adhesives derived solely from fossil fuel based phenol and proposed a novel higher value-added application of the largely available barks from the mountain pine beetle-infested lodgepole pine trees.

Phenol formaldehyde (PF) resol resins have long been used widely as wood adhesives due to their excellent bonding performance, water resistance and durability. With the growing concern for fossil fuel depletion and climate change, there is a strong interest in exploring renewable biomass materials as substitutes for petroleum-based feedstock. Bark, rich in phenolic compounds, has demonstrated potential to partially substitute phenol in synthesizing bio-based PF resins. In this study, acid-catalyzed phenol liquefaction and alkaline extraction were used to convert mountain pine beetle (MPB; Dendroctonus ponderosae) infested lodgepole pine (Pinus contorta) barks to phenol substitutes, liquefied bark and bark extractives. Two types of bio-based phenol formaldehyde (PF) resol resins, namely liquefied bark-PF resin and bark extractive-PF resins, were then synthesized and characterized. It was found that acid-catalyzed phenol liquefaction and alkaline extraction were effective conversion methods to obtain phenol substitute with the maximum yield of 85% and 68%, respectively. The bio-based PF resol resins had higher molecular weights, higher polydispersity indices, shorter gel times, and faster curing rates than the lab synthesized control PF resin without the bark components. Based on the lap-shear tests, the bio-based PF resol resins exhibited comparable wet and dry bonding strength to lab PF resin and commercial PF resin. The post-curing thermal stability of the bio-based PF resins was similar to the lab control PF resin. The liquid-state 13C nuclear magnetic resonance (NMR) study revealed significant influences on the resin structures by the inclusion of the bark components. Methylene ether bridges, which were absent in the lab PF resin, were found in the bio-based PF resins. The bark components favored the formation of para-ortho methylene linkages in the bio-based bark extractive-PF resins. The liquefied bark-PF resin showed a higher ratio of para-para/ortho-para methylene link (-CH2-), a higher unsubstituted/substituted hydrogen (-H/-CH2OH) ratio and a higher methylol/methylene (-CH2OH/-CH2-) ratio than the bark extractive-PF resin. Both tannin components of bark alkaline extractives and phenolated barks contributed to the acceleration of the curing rate of the bio-based resins. This research demonstrated the promise of the bio-based PF resins containing either bark alkaline extractives or liquefied barks as environmentally friendly alternatives to PF adhesives derived solely from fossil fuel based phenol and proposed a novel higher value-added application of the largely available barks from the mountain pine beetle-infested lodgepole pine trees.

The August 17, 1999 Kocaeli-Turkey Earthquake (Mw=7.4) caused severe damage to the structures and lifelines in the Marmara region. Soil liquefaction was identified as one of the major causes of this damage. The aim of this study is to determine geotechnical and earthquake engineering factors that contribute to the structural damage observed in Sakarya city after 1999 Kocaeli Earthquake. For this purpose, the results of an extensive field investigation program compiled by General Directorate of Disaster Affairs including subsurface soil characterization and documenting structural performance data were used. The database was carefully screened for poor quality data and was transferred to geographic information system (GIS) framework. Maximum likelihood methodology for the probabilistic assessment of seismically induced structural performance was chosen as the statistical tool. After series of sensitivity analyses, important geotechnical and earthquake engineering parameters of the problem were selected as i) liquefaction severity index, ii) post liquefaction volumetric settlement, iii) peak ground acceleration and, iv) spectral acceleration defined at the period range of conventional buildings. In addition to these parameters, structural performance defined as a) no damage and light, b) moderate damage, c) heavy damage and collapse, as well as the number of storeys of each structure were used as to correlate structural damage with geotechnical earthquake engineering factors. As a conclusion series of vulnerability functions specific to Adapazari shaken by Kocaeli Earthquake were developed. Performance predictions of these vulnerability functions were shown to be consistent with as high as 65 percent of the observed structural performance.

Traditionally, void ratio, e has been used as a state variable for predicting the liquefaction behaviour of soils under the Critical State (Steady State) framework. Recent publications show that void ratio, e may not be a good parameter for characterizing sand with fines as the steady state, SS data points move downward in e-log(p) space up to certain fines content termed as threshold fines content, TFC. Thus, it was difficult to apply SS concept on sand with fines as a small variation of fines content may lead to different SS line. Many researchers proposed to used equivalent granular void ratio, e* as an alternative state variable (i.e. in lieu of void ratio, e) in attempt to obtain a narrow trend line for SS data points irrespective of fc provided fc  TFC. The e* is obtained from e. For the conversion from e to e*, one need a parameter b which presents the active fraction of fines in overall force structure of sand. However, predicting the b is problematic. Most, if not all, of the b reported were determined by case-specific back-analysis, that is, the b-value was selected so that the test results for a given sand-fines type could be correlated with the equivalent granular void ratio, e* irrespective of fines content. This thesis examines the factors that affecting the b value by examining published work on binary packing. This leads to a simple semi-empirical equation for predicting the value of b based onparticle size ratio,  and fines content, fc. Published data and experimental results on Sydney sand appears to be in support of the proposed equation. The single relation of SS data points in e*-log(p) space for sand with fines is referred as Equivalent Granular Steady State Line, EG-SSL. The EG-SSL is then used to define the equivalent granular state parameter,*. A good correlation observed between * and q-p, q- q responses in undrained shearing. The e* and * are also used to modified a state dependent constitutive model. Seven model input parameters are needed in addition four to critical state input parameters. These parameters are obtained from drained test. The model is used to predict q-pand q- q responses for flow, non-flow and limited flow behaviour for 0% to 30% fines contents. The model predictions are in good agreement with experimental results. The effect of fines types (in terms of plasticity and angularity) on the prediction equation of b are also examined with four different types of fines. A negligible effect of fines type on the prediction equation of b is observed. The link between monotonic and cyclic loading behaviour for sand with fines are also examined with emphasis on cyclic instability and strain hardening behaviour after quasi steady state, QSS for a range of fines contents (provided that fc < TFC). It is found that a single set of rules could be used to correlate monotonic and cyclic behaviour for a range of fines contents at same *.

Thesis (M.App.Sc.) - Carleton University, 2006. / Includes bibliographical references (p. 165-175). Also available in electronic format on the Internet.

Thesis (M.App.Sc.) - Carleton University, 2006. / Includes bibliographical references (p. 151-155). Also available in electronic format on the Internet.