1,362 research outputs found
Infomania : newsletter of the Jotello F. Soga Library, Faculty of Veterinary Science, University of Pretoria November 2023
No full textNewsletter with articles and photos about what's happening at the Jotello F. Soga Library, Faculty of Veterinary Science, University of Pretoria.From the desk of the editor / Tertia Coetsee -- Jotello F Soga Library planned renovations / Tertia Coetsee -- Learning and Sharing: from Open Science to Statistics / Myleen Oosthuizen -- Vet Alumni author donate two of her debut novels / Myleen Oosthuizen -- Veterinarian donating her collection over a career lifespan / Myleen Oosthuizen -- LIASA Conference / Maria Mtsweni -- New e-books in our collection / Tertia Coetsee -- Anti-Discrimination and Social Justice week / Mathuloe Moshidi -- Book donation / Tertia Coetsee -- Welcoming new staff member / Tertia Coetseeab202
Recent Developments to Improve the Numerical Accuracy
No full textGreen Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Numerical Analysi
Fracturing Pressure in Clay
No full textHydraulic fracturing in clayey soils can be triggered by either tensile or shear failure. In this paper, the physical meanings of various equations to predict fracture initiation pressure proposed in the past are discussed using the cavity expansion theory. In particular, when fracturing pressure is plotted against initial confining pressure, published laboratory test results as well as analytical models show a linear relationship. When the slope is close to 2, fracture is initiated by tensile failure of the clay, whereas when the slope is close to 1, it is initiated by shear failure of the clay. In this study, the analytical models, validated only on laboratory test data to date, were applied to unique data from field grouting work in which extensive soil fracturing was carried out to improve the mechanical characteristics of the soft silty clay underlying a bell tower in Venice, Italy. By a careful assessment of initial confining pressure in the field, the variation in recorded injection pressures with confining pressure was examined. Results suggest that the fractures at this site were likely to be initiated by shear failure of the clay, and the values were similar to what was predicted by the model with the shear failure criterion
An approach to evaluate the efficiency of compensation grouting
No full textCompensation grouting is often employed as a mitigation technique to reduce the settlements induced by tunnelling. The efficiency of compensation grouting, defined as the ratio of the volume of heave induced at ground surface to the volume of injected grout, is strongly dependent on grout properties, injection characteristics and soil properties. In clayey soils, site observations and laboratory tests show high values of compensation efficiency immediately after injection. However the efficiency can decrease with time if positive excess pore water pressures develop in the soil during the injection process. Conversely, in sandy soils, a loss of volume occurs due to pressure filtration of the grout during and soon after the injection process, which reduces the compensation efficiency. This paper describes an analytical model that can be used to evaluate the volume loss produced by pressure filtration of cement-bentonite grouts as a function of soil, grout and injection parameters. The magnitude of pressure filtration is evaluated as the grout efficiency, which is given by the ratio of the volumes of the final grout body to the injected grout. Results show that the grout efficiency increases with decreasing soil permeability and with increasing grout bentonite content. The result of a grout injection test on a silty soil is back-analysed using this approach in which the grout efficiency is first evaluated through the proposed filtration model and then used to calibrate a numerical simulation of the test. The good agreement between experimental data and computed results shows that prediction of the efficiency of compensation grouting can be improved using the proposed approach
Experimental and numerical study of grout injections in silty soils
No full textCompensation grouting is increasingly employed as a mitigation technique of settlements induced by tunnelling and its effectiveness both in clayey and sandy soils is reported in a wide number of case histories. However, the results are highly dependent on grout properties, injection characteristics and soil properties. An experimental study was conducted to investigate the parameters that control grout injections in silty soils. The results from one injection test in a large sample of silty soil show that the compensation efficiency, defined as the ratio of the volume of heave obtained at ground surface and the injected grout volume, is much lower than one and tends to decrease with time, while the initial volume of grout lost due to pressure filtration is small. Finally, results from finite elements back analyses of the laboratory test show that a good agreement with the experimental data can be obtained if the development of large strains is taken into account
Subversive subservience' : a comparative study of the responses of Tiyo Soga and Mpambani Mzimba to the Scottish missionary enterprise
No full textBibliography: leaves 240-253.My thesis is that early African Christians engaged in critical dialogue with their missionary counterparts in a variety of ways and forms which served to challenge and enrich the Christianization process in South Africa, eventually giving rise to the emergence of African Christianity and theologies. My aim is to show that African Christians talked back in the long conversation with the European missionaries, ""a conversation full of arguments of words and images."" ¹ Early African Christians used various strategies and ways of responding to the missionary encounter ranging from overt to covert forms of resistance and negotiation. These were related to conditions on the ground. African Christian responses thus contradict any assertion of total conformity to the colonial missionary praxis. The classics debate at Lovedale, for instance, reveals that despite the apparent conformity and obedience to orthodoxy at the official level there was an awareness of ambivalence at a secondary (hidden) level. It is this awareness rather than the obvious ambivalence that is crucial to us
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