The problem of domestic solid wastes buried in landfill sites is viewed from the aspect of leachate contamination and migration in the substrate. Generally, this occurs through the penetration of the contaminant into the liner material. This study assesses the efficiency of natural clay barriers as an expedient economic lining material. / Various chemical constituents of the landfill leachate of an actual waste containment site at Lachenaie (35 km east of Montreal) were determined from samples collected from specially designed basins. / In companion laboratory tests, these leachate samples were permeated through laboratory columns that contained the natural clay compacted at the optimum water content. The columns were constructed so as to permit simulation of slow, saturated, anaerobic flow of leachate through the clay lining surrounding the landfill and leachate basins. Leachates were permeated through the soil columns for periods of four to five months, during which effluents were collected periodically and analyzed for different chemical species and physical parameters. These chemical analyses measured changes in the concentration of: (a) cations (Na, K, Ca, and Mg), (b) anions (Cl, HCO$ sb3$, and CO$ sb3$), (c) total organic carbon (TOC), and (d) heavy metals (Fe, Zn, Pb, and Cu). The physical parameters measured included: (a) pH, and (b) specific conductivity. / Subsequent to the leaching tests, the column contents were cut into six sections and analyzed to determine the distribution profiles of the adsorbed and retained contaminants at various time durations. / Predictions, using a dispersion-convection model for concentration profile development for either adsorbed or retained contaminants, were compared with the experimentally determined profiles (both in leaching columns and landfill laboratory model). / Another set of experiments was also conducted to evaluate the effect of some organic fluids on the geotechnical properties of different clay soils (natural clay and two reference clay soils: illite and kaolinite). / The results from this study have demonstrated that the natural clay soil can be used to adequately contain the different contaminant species usually present in the leachate solutions. Furthermore, the data suggested that under favourable soil conditions, landfill leachates containing low levels of trace metals will not pose a substantial contamination threat to the subsurface environment, provided that a proper thickness of barrier is used. (Abstract shortened with permission of author.)

The thesis deals with the study of soil composites that are constructed by combining regions of soft clay and granular materials in various spatial configurations. The underlying basis for the work stems from the practical application of the results of the research to offshore land reclamation practices. Due to depletion of local coarse-grained soil sources and the high cost of imported granular fill, the use of dredged and excavated marine clay has become the preferred source of materials in reclamation activities. A common reclamation technique involves placing dredged clay lumps directly on top of other layers; these lumpy fills contain large initial inter-lump voids with the result that the fills experience substantial compression purely due to the closure of the void space. A practical solution therefore is to fill the void space with a granular soil to enhance the load-carrying capacity and to minimize the settlements of the reclaimed fills. / In this research a coordinated experimental investigation was undertaken to examine the consolidation behavior of composites fabricated using a number of spherical and disk-shaped clay inclusions placed within an artificial granular medium (ballotini). The results of this experimental research program indicated that the volume fraction, shape, configuration and the constitutive properties of both the clay inclusions and the granular component are all important factors that could affect the mechanical response of the soil composites. A computational scheme, validated using the results of the bench-scale experiments, was used to analyze the response of an idealized composite lumpy fill subjected to self-weight stresses, surcharge and a load applied through a rigid footing. The computational results indicated that the consolidation behavior of the composite lumpy layers can be significantly influenced by the volume proportion, location and configuration of the clay inclusions interspersed within the granular fill. The incorporation of the constitutive behaviors of the soil components, used in reclamation activities, into such a computational analysis could assist engineers in designing reclaimed fills where the least ultimate settlement occurs within the shortest time.

Under intensive farming, soil structure degradation and soil erosion are primarily associated with losses of organic matter. Restoration of soil structure may depend on the amount and nature of the organic amendment added. The effect of the addition of humic and fibric materials, and beeswax, a naturally occurring source of long-chain aliphatics comparable to those present in humic materials, on microbial activity and the structural properties of a waterlogged silty clay low in organic carbon was investigated. The incorporation of the fibric material increased the microbial activity in proportion to the amount of material added, whereas the humic and beeswax materials had the opposite effect. All organic materials added increased the cohesion of aggregates due to non water-dispersible cements. The fibric material was predominantly composed of polysaccharides and large quantities were required to produce a positive effect. The humic material was mainly lipids and the effect was associated with the time of incubation rather than the amount of material added. Principal-component analysis showed that the humic material was more effective at stabilizing soil aggregates than the fibric material, although the fibric material had a greater effect on the resistance of aggregates to slaking forces. Further testing with beeswax showed that the clay-associated lipids increased by 3.5-4.0 times the resistance of soil aggregates to the slaking forces, whereas the effect of hydrophobic "free" lipids was transient and accessory by coating and embedding soil aggregates.

The subgrade under a rail track, also known as the formation layer, performs a vital role in rail track stability. Its primary function is to withstand load imposed from rolling stock distributed through the track structure. Since common practice is to build rail track on the natural surface of the land, there is a considerable inherent variation. Problem soils such as expansive clays are common in Australia, which can suffer significant decreases in strength and stiffness when the soil moisture state is altered. A weak formation layer may experience plastic deformation and possibly shear failure leading to sever track geometry problems. Although there are many existing methods to remediate the causes of a loss in track geometry, most are expensive and also require track closure. / Thesis (MEng(CivilEngineering))--University of South Australia, 2006.

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.

Thesis (Ph. D. - Renewable Natural Resources)--University of Arizona, 1991. / Includes bibliographical references (leaves 287-296).

Thesis (M.S.)--Ohio University, August, 1996. / Title from PDF t.p.

Thesis (M.S.)--University of Texas at El Paso, 2008. / Title from title screen. Vita. CD-ROM. Includes bibliographical references. Also available online.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1958. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 71-76).

Thesis (Ph. D.)--Lehigh University, 2002. / Includes vita. Includes bibliographical references (leaves 151-157).