No description available.

With the aim to achieve a better understanding of the time- and rate-dependent behaviour of unsaturated clays, particularly stiff natural clays, a critical review of the literature and a program of laboratory testing were carried out as part of this research. With emphasis on examining the effect of suction on viscous response, mainly primary and secondary consolidation (creep), stress-relaxation, and rate-dependency, a series of conventional multi-stage loading (MSL) oedometer tests, long-term single-stage loading (SSL) oedometer tests, and advanced constant-rate-of-strain (CRS) oedometer tests were carried out on natural and corresponding reconstituted specimens of a stiff clay namely, London Clay, retrieved from a site in the Isle of Sheppey, UK. The results obtained provide a significant contribution to the existing database and address important knowledge gaps highlighted from the literature review. The experimental studies performed included; a) An investigation of the effect of water reservoir surface roughness on the cavitation mechanism and performance of a newly designed high-capacity tensiometer (HCT), with regard maximum sustainable suction (smax) and maximum duration of measurements (tmax). b) An examination of the influence of soil suction on the primary and secondary consolidation of natural and reconstituted London Clay from a set of MSL and SSL oedometer tests. c) Characterisation of the stress-relaxation behaviour of the reconstituted London Clay subjected to suction and strain-rate variations from a set of CRS oedometer tests in an in-house designed suction-monitored cell. d) An examination of the coupled effects of suction and strain-rate on one-dimensional (1D) stress-strain response of reconstituted London Clay. Based on the experimental findings, the validity of the empirical relationships proposed in the literature for correlating time- and rate-dependency coefficients was examined and necessary modifications were proposed. The main experimental findings can be outlined as: - The mechanism of cavitation in tensiometers is indeed influenced by the surface roughness of the water reservoir. The new approach for expanding the range and duration of suction measurements for a newly designed HCT, based on hydrophilic coating of the reservoir walls, sounds promising. - The compression index (Cc) and creep index (Cαe) and the ratio α = Cαe/Cc for Sheppey London Clay are stress- and suction-dependent. The hypothesis of constant α for natural clays, as suggested by Mesri et al. (1994), is therefore rejected. - The volumetric creep deformations of unsaturated stiff clays appear to be relatively simply modelled by a creep law based on a power function. - A coupled effect of suction and strain-rate on 1D compression response was identified. At a constant suction, the higher the strain-rate, the higher the apparent preconsolidation pressure (σ'p). Similarly, at a constant strain-rate, the higher the suction, the higher the σ'p. - The values of relaxation coefficient (Rα) differ in saturated and unsaturated states. However, a clear relationship between Rα and suction was not found. The Rα = Cαe/Cc relationship, suggested by Yin et al. (2014) for saturated soft clays, appears, with an approximation, to be valid for the unsaturated stiff London Clay in the range of applied vertical stresses and soil suctions in this study. - The process of stress-relaxation in unsaturated clays is highly influenced by factors such as soil suction, pre-relaxation strain, stress, and strain-rate.

Resumo: Em um país de grande extensão territorial como o Brasil, são comuns faixas de dutos com muitas centenas e até milhares de quilômetros. Eles atravessam lugares com diversidade morfológica, rios, ambientes da costa marinha e áreas metropolitanas. A partir do momento em que o duto é instalado, este passa a sofrer influência do ambiente e também causar impacto ao mesmo, como vazamentos, e pesquisas têm interesse nestas questões porque estas envolvem a integridade dos dutos e comprometem o abastecimento dos derivados de petróleo. Neste contexto, este trabalho visa analisar a pressão da cobertura e uso da terra em faixas dos dutos Rio - Belo Horizonte, localizadas em três municípios do Estado do Rio de Janeiro, no período de 1986 a 2005, com a utilização de técnicas de geoprocessamento. Para a identificação e avaliação das pressões dos impactos humanos nas faixas de dutos, foram utilizados dados multitemporais e técnicas de detecção de mudanças. As análises de uso e ocupação da terra consideraram as relações dos sistemas de relevo em áreas de influência dos dutos. A partir destas primeiras análises, um índice de pressão antrópica (IPAd) foi proposto para analisar de forma conjunta as classes de uso e ocupação da terra. O mapa de IPAd e o mapa de variação de IPAd, possibilitaram a identificação de áreas de maior e menor pressão antrópica à faixa de dutos, bem como a variação desta pressão ao longo do período analisado. / Abstract: In a country with a great territorial extension as Brazil, pipelines with a lot of hundreds and even thousands of kilometers are common. They cross morphologic diversity places, rivers, coastal marines environments and metropolitan areas. After their installation, the pipelines suffer environmental influence that can cause impacts on them, as emptying, and some researchers have interest in these questions because it involves the pipeline integrity and compromise the supplying of oil derivates. In this context, this work aim to analyze the pressures of land use and land cover on Rio - Belo Horizonte pipelines strip, located in three municipal districts of Rio de Janeiro State, during 1986 to 2005, with geoprocessing techniques. To identify and evaluate the pressures of human impacts on the pipelines strip, multi-temporal datasets and change detection techniques were used. The analyses of land use and land cover considered the relationships of relief systems in some areas of pipeline influence. From these first analyses a pressure human index (IPAd) was proposed for pipelines strip, objecting an integrated study form between land cover and land use classes. The IPAd map and IPAd variations map, enabled the identification of areas with high and low pressure human for pipelines strip, as well as a variation of the pressures over the analyzed period. / Orientador: Paulina Setti Riedel / Coorientador: Mara Lúcia Marques / Banca: Cenira Maria Lupinacci da Cunha / Banca: Diana Sarita Hamburger / Mestre

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Civil Engineering, 1981. / Vita. / Bibliography: leaves 232-235. / by Mark Hing Chuen Chan. / Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Civil Engineering, 1981.

The research presented in this thesis focuses on the spatial variability of the Keswick and Hindmarsh Clays within the Adelaide city area. Keswick Clay is locally significant since many of Adelaide's multi-storey buildings are founded directly on it, and internationally significant, since it has been shown by Cox (1970), that this clay exhibits remarkably similar properties to those of the well-documented London Clay. The assessment of the small-scale variability of the undrained shear strength of these clays is based on measurements obtained using the electrical cone penetration test (CPT), and a micro-computer based data acquisition system, designed specifically for this study. A significant feature of the data acquisition system is that it enables measurements to be obtained at intervals of 5 mm, both reliably and efficiently. The development of the data acquisition system is discussed, and the accuracy of its measurements is examined. The small-scale variability of the undrained shear strength of the Keswick Clay is based on more than 200 vertical CPTs, performed within an area of 50 X 50 metres at a site located in the Adelaide city area. The CPTs were spaced at lateral intervals varying between 0.5 and 5 metres, with each vertical CPT extending to a typical depth of 5 metres. In addition, the small-scale horizontal spatial variability of the Keswick Clay is examined using an electrical cone penetrometer driven horizontally into the face of an embankment, again located within the Adelaide city area. The accuracy of the CPT measurements is examined, and discussion is given of the shortcomings associated with a commonly used technique, by Baecher (1982), for estimating the random measurement error associated with various test procedures. The assessment of the large-scale spatial variability of the undrained shear strength of the Keswick and Hindmarsh Clays is founded on a data base of geotechnical engineering properties, compiled from a number of consulting engineering practices and government instrumentalities. The data base, known as KESWICK, contains approximately 160 site investigations, 380 boreholes, and 10,140 measurements obtained from a number of different laboratory and in situ tests. In addition, KESWICK is used to establish generalised trends and bounds, associated with the various geotechnical engineering design properties contained within the data base. The techniques of random field theory and geostatistics are used to quantify, model and predict the spatial variability of the Keswick and Hindmarsh Clays. These techniques are compared with one another in order to assess the suitability and shortcomings of each, when applied to the study of the spatial variability of geotechnical engineering materials. Furthermore, a number of specifically-written computer programs, which were developed to enable the various spatial variability analyses to be performed, are discussed. It is demonstrated that the lateral undrained shear strength of the Keswick Clay, within the Adelaide city area, exhibits a nested structure; that is, one which is the compound effect of several genetic sources of spatial variation. In addition, it is shown that this nested structure can be adequately modelled by means of a spherical semivariogram model. The nested structure is used, together with the kriging estimation process, to provide preliminary estimates of the undrained shear strength of the Keswick Clay, within the Adelaide city area. The analyses demonstrate that the nested model and the kriging process provide a useful facility for generating preliminary estimates of the strength of the clay. Finally, the significance of the spatial variability of the undrained shear strength of clay soils is examined, with reference to the design of embankments and pile foundations. It is demonstrated that the correlation distance can greatly influence the design of each of these geotechnical systems. / Thesis (Ph.D.)--Dept. of Civil and Environmental Engineering, 1995.

University of Macau / Faculty of Science and Technology / Department of Civil and Environmental Engineering

published_or_final_version / Civil Engineering / Master / Master of Philosophy

published_or_final_version / Geography and Geology / Master / Master of Philosophy

No description available.

The Canadian National Memorial Site, near Vimy, Artois, France, commemorates the WWI Battle of Vimy Ridge; where all four divisions of the young Canadian Corps fought together with the British Forces to liberate the French ridge. Today, trench systems and an extensive subterranean network of tunnels underlie the gentle landscape of the park, which is visited each year by hundreds of thousands of tourists. Failure within these excavations is expressed as local subsidence and is potentially hazardous to the public. The following research identifies the geologic factors that influence instability in the excavations and how these factors vary both with depth and lateral extent. The Artois region of northern France is underlain by Upper Cretaceous chalk with a thin veneer of Paleocene sediments. Structure is dominated by the northwest-southeast trending Weald-Boulonnais anticlinorium. Three principle geological controls govern failure within the excavations at the Vimy site; lithologic variations, structural geometry and carbonate dissolution. An extensive stratigraphic study identified variable horizons such as chalk marls, nodular chalks, hardgrounds and flint seams, which affect the strength, permeability and structure of the rockmass. Structural geometry in the chalk varies with depth and clay content. Orthogonal fracture patterns are typical in pure carbonate rockmasses whereas inclined conjugate sets occur in clay-rich chalk. Three failure mechanisms were observed in the Vimy excavations that vary with structure and lithology. Beam failure via block fall-out is observed in pure chalk with subhorizontal and subvertical structures. Ravelling, the upward propagation of roof failure, is typical of closely spaced inclined jointing, and is also observed in shallow clay-rich lithologies. Finally, dissolution pipes occur at the intersection lineations of conjugate joint sets, and are also typical of clay-rich lithologies. Dissolution by meteoric groundwater is identified as the third geologic control and results in a decrease of intact strength, weakening of joint surfaces and overall loss of confinement in the rockmass, thereby initiating the failure modes described previously. These extensive geologic studies pinpoint the origins and variability of instability in the rockmass at the Vimy site. / Thesis (Master, Geological Sciences & Geological Engineering) -- Queen's University, 2007-12-21 11:08:16.522