The vegetation of the sand dunes on Long Beach, Vancouver Island, was studied on 116 sample plots. The purpose of this study was to describe the floristic and edaphic characteristics of the plant associations, to determine the major environmental factors controlling the distribution of the plant communities and to study the successional trends of the vegetation. The vegetation was described using the analytical and synthetical methods of the Zurich-Montpellier school of phyto-sociology. This thesis describes seven plant associations and four variants. The vegetation units are as follow: A. Foreshore habitats 1. Cakiletum edentulae B. Blowout habitats 2. Poetum macranthae a. poosum macranthae , b. abroniosum latifoliae 3. Arctostaphyleto-Rhacomitrietum canescentis C. Habitats of the mobile dune ridge 4. Elymetum vancouverensis a. ammophilosum arenariae b. elymosum vancouverensis D. Habitats of the dune slack and stable dune ridge 5. Aireto-Ceratodontetum purpurei 6. Arctostaphyleto-Eurhynchietum oregani 7. Hetergenous communities i n moist dune slack habitats E. The dune forest habitat 8. Piceeto-Gaultherieto-Maianthemetum dilatati Important environmental factors which control the distribution of these associations are the level of winter and storm tides, wind, the amount of sand burial and blowout that occurs in the habitat and the amount of available soil water. The first stages of succession begins in the unstable habitats of the Elymetum vancouverensis and Poetum macranthae. With stabilization of the habitat, these associations are succeeded by the Aireto-Ceratodontetum purpurei and the Arctostaphyletum-Eurhynchietum oregani in exposed habitats and the Arctostaphyleto-Rhacomitrietum canescentis in habitats well protected from wind. All vegetation eventually reaches the climax Piceeto-Gaultherieto-Maianthemetum dilatati. / Science, Faculty of / Botany, Department of / Graduate

Mamelodi Quarries, which currently mine the Franspoort nepheline syenite, produces aggregate and crusher sand for the local building industry. The mine is located northeast of Pretoria, South Africa on the road to Cullinan. The aim of this study is to investigate the use of the Franspoort nepheline syenite as an alumina and alkali resource for the glass and ceramics industry at Mamelodi Quarries, and to evaluate the production of a concentrate of zircon and rare earth elements as economic by-products. International standards require a nepheline product with a ferric oxide content of less than 0.35 weight percent. The Franspoort nepheline syenite contains 3.37 weight percent of ferric oxide. The iron-containing minerals present are aegirine, aegirine-augite, magnetite, ilmenite and pyrite. The removal of iron-bearing minerals was attempted by high-intensity wet magnetic separation, low-intensity dry magnetic separation, spiral gravity separation, and heavy liquid separation to produce a saleable nepheline product. This product is the cleaned final concentrate, of the different separation tests, which contains the lowest iron concentration for application in the glass and ceramic industry. The mineral assemblage was determined with a petrographic study as well as X-ray diffraction and electron microprobe analyses. Material from the different separation tests was analysed with X-ray fluorescence to obtain the chemical composition and to evaluate the final iron content of the nepheline product. The dry magnetic separation method produced the best results. The nepheline product has a ferric oxide content of 0.68 weight percent compared to the starting concentration of 3.37 weight percent. The ferric oxide concentration is, however, above the accepted levels for the glass and ceramics industry. The ferric oxide content is attributed to small iron-rich mineral inclusions, which are locked in feldspar and nepheline. The final nepheline product is not suitable for the use in the glass and ceramic industry. Zircon was concentrated the best by the use of heavy liquid separation. Zircon is in most cases locked in the minerals albite, microcline, and nepheline. The rare earth elements are mostly associated with zircon and fluorite and therefore it will not be viable to produce it as a by-product. Copyright / Dissertation (MSc)--University of Pretoria, 2010. / Geology / unrestricted

Magister Scientiae - MSc / The complex nature and composition of regolith cover in Southern Africa is a major challenge to geochemical mapping for concealed mineralization. Some of the setbacks to successful geochemical exploration may be ascribed to the use of various partial extraction techniques,without a profound understanding of the regolith components and their composition. This investigation therefore focuses on the use of hydroxylamine partial extraction geochemistry for geochemical mapping in regolith over two contrasting environments viz; aeolian sand-calcrete regolith over Au mineralization at Amalia Blue Dot Mine in South Africa and lateritic regolith covering the Ni-Cu deposit at Kabanga Main and Luhuma in Tanzania. Regolith samples from the above areas were sieved and extracted with hydroxylamine hydrochloride solution and analyzed for multi-element by AAS and ICP-MS techniques. A stepwise optimization of the hydroxylamine extraction technique of samples from both areas was carried out and incorporated into the analytical programme (in a pilot study). Results of hydroxylamine partial extraction generally gave better anomaly contrast and reflection of bedrock mineralization than the conventional aqua regia techniques that were previously used in the region. The results however show that lateritic regolith may be best extracted using 0.25M hydroxylamine while 0.1M concentration appears most suitable for extraction of aeolian-calcrete regolith. The above results are corroborated by principal component analysis of the analytical data that show various element associations, e.g. with Fe-Mn oxides while others possibly belong to the loosely adsorbed or exchangeable group. The gochemical maps in the pilot study areas at Amalia, Kabanga and Luhuma show elevated element contents or clusters of anomalies of diverse elements associated with Fe-Mn oxides. Geochemical mapping at Kabanga with deeply concealed mineralization however shows variability of subdued element patterns over mineralized areas. Geochemical signatures associated with hydroxylamine hydrochloride partial leach are therefore characterized by a lower geochemical background than that using conventional aqua regia leach. This study leads recommending for further investigations into partial extraction of the exchangeable group of elements, possibly using ammonium acetate. / South Africa

Retaining walls (RW) are among the most common geotechnical structures. They have been widely used in railways, bridges (e.g. bridges abutment), buildings, hydraulic and harbor engineering. Once built, the RW can be exposed to dynamic loads, such as those produced by earthquakes, machines, vehicles and explosions. They must remain operational in aftermath of the natural or human-induced dynamic events. Hence, the understanding of the geotechnical response of RW to these dynamic loads is critical for the safe design of several civil engineering structures such as railways, highways, bridges, and buildings. Although fairly reliable methods have been developed for assessing and predicting the response of RW to dynamic loads induced by earthquakes, there is very little information to guide engineers in the design of RW that are exposed to surface explosions (surface blast loadings). These methods for assessing RW response to earthquake loads cannot directly be applied to the design of RW subjected to surface blast loads. Indeed, blast loads are short duration dynamic loads and their durations are very much shorter than those of earthquakes. The predominant frequencies of a blast wave are usually 2-3 orders of magnitudes higher than those of earthquake wave, and the same can be said for blast wave acceleration as compared to the peak acceleration that results from an earthquake. Thus, RW response under blast loading could be significantly different from that under a loading with much longer duration such as an earthquake. There is a need to increase our understanding of the response of RW to surface explosion loadings since there is a significant increase of terrorist threat on important buildings and some lifeline infrastructures. Transportation structures (bridges, highway, and railway) are unquestionably being regarded as potential targets for terrorist attacks. The purpose of this PhD research is to investigate the geotechnical response of reinforced concrete retaining wall (RCRW) with sand as a backfill material to surface blast loads. The soil-RW model was subjected to a simulated blast load using a shock tube. The influence of the backfill relative density, backfill saturation, blast load intensity, and live load surcharge on the behaviour of RCRW with sand backfill was studied. The dimensions of the stem and heel of the retaining wall in this study were 650 mm (height) x 500 mm (width) x 60 mm (thickness) and 400 mm (width) x 500 mm (length) x 60 mm (thickness), respectively. Soil-RW model was placed inside a wooden box. The overall height of the box was 1565 mm. The retained backfill extended behind the wall for 1300 mm. Based on the results, it is found that the maximum dynamic earth pressures were recorded at a time greater than the positive phase duration regardless of the backfill condition. The total earth pressure distribution along the height of the wall showed that the magnitude of total earth pressure for loose and medium backfill at the mid-height of the wall slightly exceeded the dense backfill. In addition, the lateral earth pressures increased with the increase in the blast load intensities. On the other hand, under the same load conditions, an increase in the wall movement was noticed in loose backfill, and a translation response mode was evident in this condition. The mobilized passive resistance of the RW backfill induced by blast load was used to determine the force-displacement relationship. Finally, the susceptibility of the RW with saturated dense sand to liquefaction was examined, and it was ascertained that liquefaction was not triggered when the RW was subjected to a blast load of 50 kPa. The results and findings of this PhD research will provide valuable information that can be used to evaluate the vulnerability of transportation structures to surface blast events as well as to develop guidance for their design.

abstract: This study evaluates the use of plant-extracted silica solution as a bio-based grout material for improvement of granular soils. Although silicate grout is a very well-established and popular technique in the ground improvement market, efforts have been initiated to replace chemically-synthesized silicate grout with plant-extracted silica grout. This initiative will increase the level of sustainability and consequently improve the existing market acceptability. The silica-rich plant source used for extraction was rice husk, which is an abundantly produced agricultural waste. The extraction method includes acid-leaching, temperature-controlled rice husk ash production and the preparation of an aqueous sodium silicate solution from the ash through an alkaline leachate method. Silica ash was in amorphous form containing 95% of silica content which is suitable for soil treatment. Gelation time was controlled in the absence and presence of sand under different pH values. Bio-based silica grouting showed an improvement of the shear strength of the soil as well as the hydraulic conductivity reduction. / Dissertation/Thesis / Masters Thesis Civil, Environmental and Sustainable Engineering 2019

The fossorial Florida Sand Skink (Plestiodon [=Neoseps] reynoldsi) inhabits a restricted range of scrub and sandhill fragments on the ridges of central Florida. The high rate of urban and agricultural development in this area necessitates conservation strategies other than land acquisition and management because of the limited remaining Florida Sand Skink habitat available. This study tests the viability of translocation as a conservation strategy for this species and assesses which features of a recipient site contribute to the successful establishment of a population. In 2007, 300 individuals were collected and moved from an intact scrub habitat, individually marked, and moved to a nearby reclaimed site with no existing Florida Sand Skink population. Fifteen 20 m² enclosures were constructed at the recipient site, and 20 skinks were randomly assigned to each. These enclosures were divided among five treatments, which were represented the range of habitat types at the donor site and differed in the presence or absence of a shade-providing object and coarse woody debris. Translocated skinks were monitored for two years to measure survival and reproduction. While survival and reproduction were apparent in all treatments, survival was significantly greater in enclosures with no shade-providing object and low soil moisture, and reproduction was most evident in enclosures with less light intensity and soil compaction. Common measurement of environmental variables at the donor and recipient sites showed that all of the recipient site enclosures differed from the donor site in the amount of vegetative cover but contained the structural heterogeneity that is associated with Florida Sand Skink presence in the wild. This study indicates that translocation is a practical conservation strategy for this species, and my results can be used to inform protocol for future Florida Sand Skink translocation efforts.

Philosophiae Doctor - PhD / This study presents the results of radiometric investigation of soil and beach sand in Zanzibar. The activity concentration of natural radionuclides (40K, and 232Th and 238U decay products) in beach sand and soil samples was measured in-situ using the NaI(Tl) and the MEDUSA gamma ray detectors and ex-situ using the low background HPGe detector system. The activity concentrations of 232Th, 238U and 40 K in beach sand are much lower than in soil samples, with one major exception at Kukuu. Two beach sand samples from Kukuu beach were found to have enhanced radioactivity levels due to the presence of heavy minerals. The spatial distributions maps for 40K, 238U and 232Th show large variation in soil samples for two relatively small islands. These strong variations are unexpected, that could have implications for agriculture, is one of the major outcomes of this study. The outdoor gamma dose rates obtained in beach sand and soil samples ranged from 3 to 2156 nGy h-1 and 50 to 294 nGy h-1, respectively. The highest absorbed dose rates in soil samples and beach sand are respectively 5 and 38 times higher than the average world level of 57 nGyh-1 for terrestrial doses (UNSCEAR, 2008). Apart from the Kukuu black sand samples that contain the high 238U and 232Th levels, the beach sands and soil in this study do not pose any radiological threat to the public using beaches for various activities. Based on elemental concentrations, the beach samples in the study area have been classified into four groups; silicate sand (rich in SiO2), carbonate sand (dominated with CaO), mixed sand (with high amount of CaO and SiO2) and heavy mineral sand (with high contents of Fe2O3 and TiO2. A strong correlation between SiO2, Fe2O3, TiO2, Zr, V, Ce, Nb, Hf, Y, La, and Nd show these elements are linked with high activity concentration of 232Th in the studied samples. Moreover, the high concentrations of Y, V, P2O5 and Fe2O3 in the beach sand samples may relate to high 238U activity concentration. This study set out to investigate how radiometric studies can quickly and easily provide an idea of the variation of soil type found over a large area as well as provide detailed information on a small scale such as the beach where heavy minerals were found. The in-situ laboratory measurements were supplemented by XRF and ICP-MS measurements of samples to investigate the distribution of heavy mineral sands.

This report presents the results of analyzing the critical void ratio concept on weakly cemented sand. The study consists of drained triaxial compression tests performed on artificially cemented sands created to simulate the natural behavior. In order to carry out this study, loose samples were prepared and subjected to different confining pressures such that failure at volumetric contraction could be obtained. The triaxial test results showed that the samples exhibited similar response to drained loading as compared to previous investigations on the static behavior of naturally and artificially cemented sands. Following the empirical method of determining the critical void ratio by plotting volumetric strain at failure against void ratio after consolidation, interpolation of the data points yielded critical void ratios of 0.735, 0.722, 0.703 and 0.668 for confining pressures of 60, 70, 80 and 95, respectively. A comparative analysis was made by plotting instantaneous void ratio during the loading against axial strain and this yielded values of 0.745, 0.735, 0.715 and 0.685 for confining pressures of 60, 70, 80 and 95 respectively. However, this method depends on the test accuracies at strain levels beyond 20% where the specimen becomes severely distorted, thus, making this method unreliable to use. Utilizing the result from volumetric strain-void ratio curves, the relationship between volumetric strain at failure and confining pressure was plotted and yielded critical confining pressures of 125, 94, 78, 67 and 60 psi for void ratios after consolidation of 0.66, 0.68, 0.70, 0.72 and 0.74, respectively. From the above results, the critical state line, which shows the variation of the critical void ratio, e_crit with the magnitude of the cr1 critical confining pressure, σ₃_crit, was defined for the artificially prepared samples with one percent cement. It would be interesting to compare this result with the critical state line of uncemented samples and of samples with higher amounts of cementation. The critical state concept is very important in evaluating the undrained strength of sands from drained tests data. The reader is referred to reference 7 since this is beyond the scope of this investigation. This concept is also an important study used in determining the liquefaction potential of sands. A paper by Castro [2] reported that liquefaction can only occur in sands that are looser than the critical state. The results of consolidated-undrained static tests will indicate whether the sand is looser or denser than the critical void ratio for the appropriate confining pressure, and thus whether the sand is susceptible to liquefaction. The reliability of the parameters obtained depends on a very limited number of data points. The author suggests that more tests on a wic!er range of relative density and confining pressure should be conducted to obtain more data points where a more accurate interpolation or extrapolation could be done. However, the results presented in this report are hoped to provide useful information for further studies to be made on the analysis of critical void ratio concept in cemented sands. / Master of Engineering

The thesis project aims to investigate a Form Finding process as a design tool as well as the generator of a structural system, in this case a process of intersecting cones to create surface network logic, for a sailing school at Lidingö, Stockholm. Specifically the research aims at the blurring of the cone shape and the diffusion of a cellular logic by a process that increases the complexity and definition of the whole system. And as a result, a design method that generates and shapes the space.

El texto completo de este trabajo no está disponible en el Repositorio Académico UPC por restricciones de la casa editorial donde ha sido publicado. / This article describes consolidated Direct Cut tests not drained in the laboratory, carried out on samples of volcanic sand from Arequipa, Peru. The samples were tested for maximum dry density and optimal moisture content; Furthermore, they were reinforced with polypropylene fibers and cement. The samples were reinforced with 0.5% cement with respect to the dry weight of the sample soil and tested at 3 days. The added polypropylene fiber has dimensions of 48 mm wide with 1.2855 mm long and 0.3325 mm thick, and they were used in different percentages regarding the dry weight of the soil sample (0.25% -0.75% -1.00% -1.25%). The results of the tests indicated that the addition of polypropylene fibers together with the cement increases the resistance to cut proportionally to the amount of fiber up to 1% of fiber, this being the best result obtained, decreasing the resistance as the percentage of polypropylene fiber.