In this thesis, some aspects concerning building embankments founded on sulphide clay are studied, with special reference to ground improvement by preloading in combination with prefabricated vertical drains (PVD’s). The main purpose of the research was to increase empirical knowledge of the mechanical behaviour of sulphide clays subjected to embankment loadings and of the interaction between vertical drains and sulphide clays. Important aspects related to ground improvement with PVD’s in more general terms are also treated, in particular how various uncertainties regarding the properties of the clay and the clay-drain interaction imposed in the design phase can be addressed. The benefits of using theobservational method for handling these uncertainties are discussed, and a description of how the method was used in an embankment project is presented. The results from the research are presented in one conference paper and two papers submitted to peer-reviewed international journals, which are appended. The design of PVD’s involves describing the consolidation characteristics of the clay and the interaction between the drains and the clay. Primarily, the rate of consolidation is determined by the hydraulic conductivity (permeability) of the clay in the horizontal direction. Hence, accurate determination of this material property is of paramount importance in making reliable design predictions. As conventional laboratory tests for assessing the consolidation characteristics of a clay only provide information about its properties in the vertical direction, one is often left to make assumptions about the horizontal properties based on empirical correlations. Reliable empirical knowledge of these correlations for a certain clay is there forevital. A large number of CRS tests were performed on horizontal and vertical samples ofsulphide clay in order to investigate the correlation between the horizontal and verticalhydraulic conductivity and coefficient of consolidation. The results show that there is very small anisotropy in these parameters and that the scatters in the results are large. For designpurposes, sulphide clays should therefore be assumed to be isotropic in this respect. In orde rto handle the variation in properties, several parallel tests should be made and partial factors of safety should be introduced in the design. Introducing partial factors of safety in the design of PVD’s is one of the main topics suggested for further research. Regarding the clay-drain interaction, a study of the disturbance effects (smear effects) during the installation of drains in sulphide clays was performed. Back-calculations of measurements of pore pressure dissipation were made via a parameter study. It was shown that smear affects the consolidation rate to some extent but that the natural (undisturbed) hydraulic conductivity is more significant. The undrained shear strength su of a clay is dependent on the preconsolidation pressure σ 'p . As the clay consolidates under a loading, the effective stress increases, possibly to magnitudes surpassing the initial preconsolidation pressure and thereby leading to increased undrainedshear strength of the clay. The relation between su and σ 'p, i.e. the ratio su /σ 'p for asulphide clay, was investigated based on results from a large number of in situ tests andlaboratory tests. There were large scatters in the measurements, but su /σ 'p =0.25 is suggested as being relevant in the direct shear zone for design purposes in sulphide clays. / <p>QC 20101101</p>

No description available.

[pt] O método empírico de Terzaghi (1943) para cálculo do recalque de adensamento primário com carregamento dependente do tempo é comparado com dois métodos propostos nesta pesquisa: o primeiro, baseado na alteração da fração de tempo em que cada incremento de carregamento é aplicado de forma instantânea, e o segundo mantendo a proposta inicial de Terzaghi (1943), porém realizando reduções percentuais do grau médio de adensamento para o período de construção e obtendo novas frações de tempo para o período pós-construção. Os resultados mostram que com a adoção das frações de tempo, apresentadas em tabelas, a diferença entre os valores do grau médio de adensamento determinados pelas curvas teórica e empírica varia entre 1,50 por cento a 3,50 por cento, dependendo das condições iniciais de excesso de poropressão. O segundo método, mais exato, apresenta diferenças menores, com ambas as curvas praticamente sobrepostas. Adicionalmente, outras duas soluções alternativas são investigadas considerando o carregamento em degraus e discretizado. Uma solução matemática rigorosa também é apresentada para representar o problema de adensamento com drenos verticais, considerando a hipótese de deformações livres. Uma comparação com a solução proposta por Olson (1977), fundamentada no conceito de deformações iguais, mostra que a hipótese de deformações iguais subestima o grau médio de dissipação dos excesoss de poropressão entre 1,15 por cento a 4,84 por cento, e que essa diferença tende a diminuir para tempos de construção elevados. Finalmente, soluções para fluxo vertical e radial combinados também são obtidas, considerando a hipótese de deformações livres e a formulação proposta por Carrillo (1942). / [en] Terzaghi s (1943) empirical method for calculating primary consolidation settlement due to ramp loading is compared with two methods proposed in this research: the first one, based on changing the fraction of time in which each loading increment is applied instantly, and the second keeping Terzaghi s initial proposal (1943), but making reductions in the average degree of consolidation for the construction period and determining new fractions of time for the post-construction period. The results show that with the hypothesis of time fractions, the difference between the values of the average degree of consolidation determined by the theoretical and empirical curves varies between 1.50 percent to 3.50 percent, depending on the initial conditions of excess poropressure. The second method is even more accurate with both curves practically overlapping. Additionally, two other alternative solutions are investigated considering step and discretized loadings. A rigorous mathematical solution is also presented to represent the consolidation problem with vertical drains, considering the hypothesis of free deformations. A comparison with the solution proposed by Olson (1977), based on the concept of equal deformations, shows that the hypothesis of equal deformations underestimates the average degree of consolidation between 1.15 percent to 4.84 percent, and this difference tends to decrease for long construction periods. Finally, solutions for the vertical and radial flow combined is also obtained, considering the hypothesis of free deformations and the formulation proposed by Carrillo (1942).

Sewer flooding incidents in the UK are being increasingly associated with the presence of blockages. Blockages are difficult to deal with as although there are locations where they are more likely to occur, they do occur intermittently. In order to manage sewer blockage pro-actively sewer managers need to be able to identify the location of blockages promptly. Traditional CCTV inspection technologies are slow and relatively expensive so are not well suited to the rapid inspection of a network. This is needed if managers are to be able to address sewer blockages pro-actively. This thesis reports on the development of low-cost, rapidly deployable acoustic base sensor that will be able to survey live sewer pipes. The sensor emits short coded acoustic signals which are reflected from any defects of the wall of the underground pipes and recorded for future processing. The processing algorithms are based on the temporal windowing, deconvolution, Fourier, and intensity analysis so that the response can be linked directly to the location and property of the of the pipe deformation. The sensor was tested in a full scale sewer pipe in the laboratory and in few sites in UK, Austria and Netherlands and it was shown that it is able to discriminate between blockages and structural aspects of a sewer pipe such as a manhole and lateral connection. The anticipated cost is orders of magnitude lower than any current technique.

No description available.

Au Québec, les drains installés dans les sols sableux-limoneux sont sensibles au colmatage par ensablement et/ou par ocre de fer. Dans le passé, les drains avec des pertuis inférieurs à 2 mm étaient utilisés au Québec avec un filtre tissé de 110 microns ou un filtre tricoté de 450 microns. Récemment, des drains avec des pertuis supérieurs à 2 mm ainsi qu’un filtre de 250 microns ont été introduits sur le marché mais n’ont jamais été testés. Le projet avait pour objectif de déterminer les vitesses auxquelles se feront l’ensablement et le colmatage ferrique pour différentes combinaisons de drains (pertuis de 1,8 mm et de 3 mm) et de filtres (110 μm, 250 μm et 450 μm) dans un sol sableux à Bécancour. Un dispositif expérimental en blocs complets (3) aléatoires a été utilisé. Les débits ont été mesurés à la sortie des drains de chaque parcelle et les hauteurs des nappes ont été mesurées avec un bulleur dans des puits d’observation. Le suivi du pH, du potentiel d’oxydoréduction et du contenu en Fe2+ a été réalisé dans l’eau de la nappe et celle des drains. Les drains excavés 13 mois après leur installation ne montrent que des traces de sédiments et de colmatage ferrique. Les niveaux de Fe2+ sont significativement plus faibles dans l’eau à la sortie des drains que dans l’eau de la nappe. Le processus de colmatage ferrique ne semble que commencer et son impact n’est pas mesurable au niveau des débits unitaires à la sortie des drains. / In Quebec, drains installed in sandy loam soils are susceptible to clogging by silt and/or by iron ochre. In the past, drains with slot widths smaller than 2 mm were used with a woven filter of 110 microns or knitted filter of 450 microns. Recently, drains with slot widths larger than 2 mm and a filter of 250 microns were introduced on the market but have never been tested. The project aimed to determine the speed at which silting and iron clogging will happen for different combinations of drains (slot widths 1,8 mm and 3 mm) and filters (110 μm, 250 μm et 450 μm) in a Becancour’s sandy soil. An experimental randomized complete block (3) design was used. The flow rates were measured at the outlet of each experimental plot and the heights of water table were measured with a bubbler in piezometers. The monitoring of physicochemical parameters (pH, redox potential and Fe2+ content) was performed in ground water and water from the drain outlet. The drains excavated 13 months after their installation only show traces of sediments and of iron ochre. Concentrations in Fe2+ are significantly lower in the water from the outlet drains than water from the ground water table. Iron clogging process seems to begin and its impacts are not measurable in terms of flow rates at the drain outlets.

The main aim of this research was to gain a better understanding of the surface and groundwater systems in order to sustainably manage the resource for both current and future generations. Three aquifers are present within the Hinds Rangitata Plain. Aquifer one extends from near surface to approximately 40 - 50 m, aquifer two occurs from approximately 40 - 90 m, and aquifer three occurs from approximately 90 - 150 m. Aquifer one is shown to occur as a series of permeable, iron stained, poorly connected and laterally discontinuous lenses, within and often separated by less permeable sandy or tight claybound gravels. Lenses range from a few centimeters to 20 m wide and from a few centimeters to 1 m thick. These permeable layers are known to be the dominant sources of groundwater from aquifer one. In all three aquifers depth to groundwater and water seasonal water level fluctuations increase with increasing distance inland from the coast. Aquifer one gains and loses groundwater along different sections of the Hinds and Rangitata Rivers. The Hinds Rangitata Plain can be broken into seven distinct zones based on differences in the dominant source (s) of groundwater recharge within each zone. The boundaries for each zone were determined by comparing the short-term seasonal water level fluctuations observed over the course of this study and the long-term water level records, with rainfall, river flows and Mayfield-Hinds Scheme recharge. The majority of the zones also have distinctly different groundwater chemistry and oxygen-18 (d18O) values. Flows in drains and the Hinds River were highly influenced by groundwater levels. Drains and springs within the Mayfield-Hinds Irrigation Scheme were highly influenced by irrigation recharge where as those closer to the coast were more influenced by rainfall. A regional water balance of the Hinds Rangitata Plain was carried out for a one period, between September 2005 and August 2006. During this period, total recharge was 375 m3 x 106, total discharge was 227 m3 x 106, and the outflow was 148 m3 x 106. Data collected during the course of this study showed that rainfall recharge was dominant, accounting for 67 % of the total recharge. The Mayfield-Hinds Irrigation Scheme accounted for 30 % of the total recharge, with a relatively small contribution each from the Rangitata Diversion Race and Hinds River. In terms of discharge, the combined discharge from the drains and Rangitata River terrace springs, accounted for 62 % of the total discharge, with the remaining discharge from coming from groundwater abstraction. There are no overall losses to groundwater from either the Rangitata River or from stockwater race.

In this thesis, the Cross-Gate SOI MOSFET that has double sources and double drains was successfully fabricated. The new SOI device structure has five unique features. First, it uses mesa isolation instead of using conventional LOCOS and trench isolation to avoid the bird¡¦s beak effect in LOCOS isolation and the complexity of digging trench in trench isolation¡F second, it has three surfaces of gate structures which can increase the effective channel width of the device to enhance the current drivability of the device without reducing the packing density of the circuit¡F third, it has four channels which can increase the current drivability of the device¡F fourth, it has narrowed source and drain that can reduce the leakage current¡F fifth, it has double sources and double drains that can design double or half current in the electric circuit by one device. According to the simulation results of the TSUPREM-4 and TMA TCAD, the saturation drain current of the multi-gate SOI devices are almost double larger than that of the conventional SOI device as VGS - Vth = 0.7 V. And the threshold voltage¡B Ion/Ioff and subthreshold factor of the Cross-Gate SOI device are almost the same with such of the Four Channels Multi-Gate SOI device. As far as the fabrication process is concerned, the new SOI device has simpler isolation processes than that of the conventional one. In addition, the nano-devices that Leff ¡× 71nm was successfully fabricated. As concerning the electrical behavior, under the same condition of Leff ¡× 71nm, Weff ¡× 440nm, tsi ¡× 120nm, the Cross-Gate SOI device has the lower subthreshold factor which is 93.153 and the higher Ion/Ioff which is 1.66¡Ñ10E5 than those of the Four Channels Multi-Gate SOI device, in addition, the Cross-Gate SOI device has no kink effect. So, it can be concluded that such the Cross-Gate SOI device presented is much more applicable to the development of low power and high speed ULSI in the nearest future.

The main aim of this research was to gain a better understanding of the surface and groundwater systems in order to sustainably manage the resource for both current and future generations. Three aquifers are present within the Hinds Rangitata Plain. Aquifer one extends from near surface to approximately 40 - 50 m, aquifer two occurs from approximately 40 - 90 m, and aquifer three occurs from approximately 90 - 150 m. Aquifer one is shown to occur as a series of permeable, iron stained, poorly connected and laterally discontinuous lenses, within and often separated by less permeable sandy or tight claybound gravels. Lenses range from a few centimeters to 20 m wide and from a few centimeters to 1 m thick. These permeable layers are known to be the dominant sources of groundwater from aquifer one. In all three aquifers depth to groundwater and water seasonal water level fluctuations increase with increasing distance inland from the coast. Aquifer one gains and loses groundwater along different sections of the Hinds and Rangitata Rivers. The Hinds Rangitata Plain can be broken into seven distinct zones based on differences in the dominant source (s) of groundwater recharge within each zone. The boundaries for each zone were determined by comparing the short-term seasonal water level fluctuations observed over the course of this study and the long-term water level records, with rainfall, river flows and Mayfield-Hinds Scheme recharge. The majority of the zones also have distinctly different groundwater chemistry and oxygen-18 (d18O) values. Flows in drains and the Hinds River were highly influenced by groundwater levels. Drains and springs within the Mayfield-Hinds Irrigation Scheme were highly influenced by irrigation recharge where as those closer to the coast were more influenced by rainfall. A regional water balance of the Hinds Rangitata Plain was carried out for a one period, between September 2005 and August 2006. During this period, total recharge was 375 m3 x 106, total discharge was 227 m3 x 106, and the outflow was 148 m3 x 106. Data collected during the course of this study showed that rainfall recharge was dominant, accounting for 67 % of the total recharge. The Mayfield-Hinds Irrigation Scheme accounted for 30 % of the total recharge, with a relatively small contribution each from the Rangitata Diversion Race and Hinds River. In terms of discharge, the combined discharge from the drains and Rangitata River terrace springs, accounted for 62 % of the total discharge, with the remaining discharge from coming from groundwater abstraction. There are no overall losses to groundwater from either the Rangitata River or from stockwater race.

Liquefaction is a costly phenomenon where soil shear modulus degrades as the generation of excess pore pressures begins. One of the methods to mitigate liquefaction, is the use of prefabricated vertical drains. Prefabricated vertical drains provide a drainage path to effectively mitigate the generation of pore pressures and aid in shear modulus recovery. The aims of this study were to define shear modulus degradation vs. shear strain as a function of excess pore pressure ratio; define the effects of prefabricated vertical drains on the behavior of pore pressure generation vs. shear strain; and to define volumetric strain as a function of shear strain and excess pore pressure ratios. A large-scale laminar shear box test was conducted and measured on clean sands with prefabricated vertical drains spaced at 3-feet and 4-feet. The resulting test data was analyzed and compared to data without vertical drains. The results show the effect of increasing excess pore pressure ratios on shear modulus and curves where developed to encompass these effects in design with computer programing like SHAKE or DEEPSOIL. The data also suggests that prefabricated vertical drains effectively mitigate excess pore pressure build-up, thus increased the shear strain resistance before pore pressures were generated. Regarding volumetric strain, the results suggests that the primary factor governing the measured settlement is the excess pore pressure ratio. This indicates that if the drains can reduce the excess pore pressure ratio, then the resulting settlement can successfully be reduced during a shaking event. The curves for shear modulus vs. cyclic shear strain as function of pore pressure ratio were developed using data with high strain and small strain which leaves a gap of data in the cyclic shear strain range of 0.0001 to 0.01. Further large-scale testing with appropriate sensitivity is needed to observe the effect excess pore pressure generation on intermediate levels of cyclic shear strain.