No description available.

Thesis (Doctoral)--Delft University of Technology, Delft, the Netherlands, 2008. / Description based on print version record. Includes bibliographical references.

No description available.

Thesis--M. Sc. (Eng.), University of Hong Kong. / Mimeographed.

The main aim of the research was to study the behaviour of a silty clay under two-way cyclic loading. Equipment was developed for the application of a sinusoidally varying deviator stress to a sample in the triaxial cell. The equipment was designed to apply deviator stresses in both compression and extension during each cycle. ii A programme of monotonic and two-way cyclic triaxial tests has been performed on samples of Keuper Marl, isotropically consolidated to a range of stress histories. The build-up of strain and pore pressure during repeated loading is discussed. A model is developed, within the framework of the critical state theory of soil mechanics, to predict the amount of pore pressure produced by a given number of loading cycles at a known stress level. An extension of the model is suggested whereby the varied loading, more appropriate to offshore foundation conditions, may be analysed. In addition, a programme of monotonic and cyclic simple shear tests has been performed. The equipment has been developed, during the course of the research, to enable the direct measurement of pore pressure during shear. At attempt has also been made to monitor the change in lateral stress during shear by means of an instrumented membrane. The results of the simple shear tests have been analysed and are presented in terms of horizontal shear stress and effective vertical stress. An attempt has been made. to deduce the principal stresses present in a sample subject to simple shear loading and a method of relating the results from monotonic tests using simple shear and triaxial devices is discussed.

This research studied the effects of the addition of ground granulated blast furnace slag (ggbs), activated by 2% calcium hydroxide (Ca(OHh, on the strength, permeability and porosity development of a laboratory prepared clay mix (kaolinite with and without 6% gypsum) and a natural sulphide-bearing clay soil, Lower Oxford Clay. Based on shear, compressive and indirect tensile strength testing, it was found that an increase in the stabiliser slag/lime ratio results in substantial strength increase even after short curing periods (up to 12 weeks). This increase in strength is more pronounced if curing is at elevated temperatures (30 °C). The presence of sulphates (6% gypsum=2.73% SO3) resulted in an accelerated increase in the strength development for stabilised kaolinite, which was comparable to that of stabilised Lower Oxford Clay. In the absence of sulphates, large ggbs additions were only activated effectively at higher curing temperatures (20 and 30 °C) after curing periods of 24 weeks and beyond, although it is suggested that 2% lime creates a sufficiently alkaline environment for activation. The degree of slag activation and thus the subsequent cementation process was reflected by an increase in the percentage of the pore volume occupied by pores with a radius ::s;0.0Sμm, which is usually associated with the pore fraction characteristic of cementitious gels. The increase in slag addition, for kaolinite mixes, was accompanied by a reduction in total porosity. Specimens made from Lower Oxford Clay exhibited a significant increase in pore volume at higher slag additions. This is interpreted as being due to the creation of pore space resulting from restrained shrinkage of gels by inert particles during drying in this coarser, natural clay. No significant trend in the effect of curing temperature on the pore size distribution could be identified from the data. The development of permeability, however, showed some sensitivity to curing temperature. Results from specimens cured at 20 and 30 °C showed an accelerated reduction in their k-values in comparison to samples which had been cured at 10 °C. However, little correlation between measured permeability and exhibited pore size distribution could be established which is believed to be due to the strong influence of shrinkage during drying prior to mercury intrusion porosimetry in the dimensionally semi-stable soil system. The volume stability of stabilised specimens during frost action was assessed in a series of 12 freeze-thaw cycles, which were carried out in accordance to the German proposal for a European Pre-Standard. Generally an increase in the curing period prior to frost action and higher overall sample porosity resulted in relatively better performance during frost action. The influence of the slag/lime and slag/gypsum ratio on the swelling potential upon soaking was assessed in long-term soaking tests and the underlying causes were identified by findings from microstructural investigations including SEM and TG analysis. These results contributed to a better understanding of the slag activation process. In an alkaline environment slag hydration appears to be triggered earlier by sulphate, due to the more intensive disturbance of a thin protective layer of cementitious products on the slag grains. Disruption of this layer, for example by ettringite formation, exposes more unreacted slag grain surface, which will subsequently start to hydrate. Findings were complemented by two case studies, one which investigated the cause of substantial heave on a German highway on a microscale and the other which assessed the technical performance and the economic implications of a full-scale trial utilising the stabilisation technique with lime and ggbs for a temporary diversion. The overall findings from the projects indicate that soil stabilisation with lime and ggbs is, particularly for soils with significant sulphate/sulphide content, a feasible and environmentally friendly alternative to the classic soil stabilisation methods.

Improving the mechanical properties of a clayey soil is one of the best options to avoid future structural failures in buildings and is cheaper than replacing all the material. Therefore, this article proposes the use of recycled glass and fan shells as reinforcement materials. This article presents an experimental study to evaluate the mechanical properties of a pure and mixed soil. The clay soil was mixed with 7% of glass (PV) and with 3%, 6%, 10%, 12% and 15% of Fan Shells (PCA) duly crushed and passed through sieve #100. Tests of sieve granulometry, sedimentation granulometry, Atterberg limits, modified proctor and drained consolidated direct cut were performed. This allowed comparing all the data obtained and defining the optimal percentage of the mixture in which the clay improves its mechanical properties. According to the tests carried out, the proportion that has 7% glass and 6% Fan Shells has better results because there is an improvement in its dry density from 1,784 g / cm3 to 1,847 g / cm3, its moisture content increases from 9.4% to 12.1%. In addition, its friction angle improves from 28.9 °to 32 °and cohesion from 0.05 kg / cm2 to 0.1 kg / cm2. These results verify that the properties of the clay soil are improved.

Minimal studies have evaluated nitrification and subsequent denitrification for soils where rice is produced in the delayedlood system. Laboratory and field experiments were conducted at USDA-ARS and the Delta Research and Extension Center in Stoneville, MS to quantify the nitrification potential of southern USA soils, and evaluate nitrogen amendments aimed to reduce nitrification rates on clay soils. The Sharkey clay soil at Stoneville, MS was one of the soils with the greatest nitrification potential. Dicyandiamide (DCD) increased the number of days that half the total recovered inorganic–N was in the ammonium–N form (half-life) by approximately 3old and 18% when compared to non-amended urea in the laboratory and field, respectively. Results suggested that nitrapyrin was not an effective nitrification inhibitor in southern soil. Coated urea (43%N) applied 12 days before flood establishment (dbf) was most successful at reducing nitrification resulting in yield comparable to urea applied one dbf.

Thesis (Ph. D.)--Carleton University, 1996. / Also available in electronic format on the Internet.

Crude oil is of economic importance to any nation. However its poor management and disposal method has resulted in oil spillage and ground contamination. Most emphasis on crude oil contamination on the environment has been on surface and ground water pollution, as well as plants and animals with little or no attention paid to the engineering properties of the contaminated soil. This research is thus aimed at investigating the effect of light crude oil contamination on the geotechnical properties of kaolinite clay soil. This research is a laboratory based experiment in which the contaminated soil was prepared by adding different percentages of light crude oil (2%, 5%, 8%, 10%, 15% and 20%) measured by weight of the dry soil sample and mixed until a uniform mixture was obtained. The British Standard Test Methods for Civil Engineering purposes BS 1377: 1990 (EUROCODE 7: EN 1997: 2-5) was adopted with few modifications. The calculations were based on the fact that the pore space in the contaminated soil is occupied by water and crude oil so water content was calculated from the fluid content and the rate of evaporation of crude oil during oven drying was also considered. The classification results showed that crude oil contamination caused an increase in linear shrinkage, liquid limit, plastic limit and plasticity index between 0% to 20% contaminations. The compaction result showed that there was an increase in maximum dry density while the optimum moisture content decreased between 0% and 15% of crude oil contamination. The result showed that the soil could not compact at 20% contamination and above. Also, the coefficient of permeability increased with increase in the percentage of crude oil contamination while the coefficient of consolidation value (Cv) increases with increase in the percentage of contamination. There was a decrease in the cohesion value and the frictional angle due to the introduction of the crude oil into the soil. Although crude oil altered the geotechnical properties of the kaolinite clay soil and reduced its strength, the soil can still be used for geotechnical purposed after remediation.