A dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of requirements for the degree of Master of Science. February 2015. / This dissertation is an assessment of the compliance with and performance of the Instream Flow Requirement (IFR) system and the Building Block Methodology for the Sabie-Sand River. Firstly, a comprehensive exploration of aspects of the ecological system in the Sabie-Sand Catchment is set out and explored in an attempt to garner an understanding of the pertinent ecological components of the river, in the form of a literature review. This is done with a view to gaining insight into where potential ecological failure may occur should flows in the Sabie-Sand be inadequate for ecological maintenance. A range of abiotic and biotic factors are investigated, and the manner in which they might change in response to changing flow conditions is set out.

Ferrosilicon containing 50-75% Si and 1.0-5.0% Zr is used as inoculant in the cast iron industry. Zr can be added to liquid ferrosilicon by use of Zr metal or zirconium ferroalloy (FeSiZr). Then the recovery of Zr, i.e. the fraction of Zr transferred from the additive to the ferrosilicon, as well as the hit rate on specification is high. The aim of this study was to investigate the recovery of Zr from zircon sand, ZrSiO4, and zirconia, ZrO2, in comparison to zirconium ferroalloy when added to liquid ferrosilicon with 75% Si at 1600⁰C.  Also the refining effect of the different additives on Al was investigated. The experiments were carried out by stirring samples of controlled amounts of ferrosilicon and Zr additive in a graphite crucible at 1600⁰C and under inert Ar atmosphere for certain amounts of time. The reaction between ferrosilicon and Zr additive was stopped by rapid cooling of the samples. ICP-OES provided the concentration of Zr and Al and LECO O/N the concentration of O. SEM-ESD was used to examine the microstructures of ferrosilicon and Zr additive after experiments. It was found that ZrO2 was reduced by Si at the particle surface to yield dissolved Zr and ZrSiO4. The ZrSiO4 additive decomposed via two simultaneous reactions, one yielding ZrO2, Si and O2 and the other Zr, Si and O2. The recovery of Zr from ZrO2 and ZrSiO4 was significantly lower than from FeSiZr. Of ZrO2 and ZrSiO4, ZrO2 yielded the highest Zr recovery; the difference was much bigger than predicted by thermodynamics. It was discussed if that could be due to a higher reaction rate of the ZrO2, caused by the smaller size (APS 1 µm compared to d50 91 µm) and larger surface area of this addition. It was also found that utilization of density differences to separate the ferrosilicon and Zr additive did not work for zirconia under the same conditions as it worked for zircon sand, although zirconia has a higher density than zircon sand. The reason was the smaller particle size of the ZrO2 powder. No refining of Al was observed.

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Understanding modern features allows for their use as analogues for understanding the environments of the past and even environments on other planetary bodies. This study uses Ground-Penetrating Radar (GPR) to image the near surface sedimentary structures on a large linear dune in the northern Namib Sand Sea and image the sedimentary structure of an auxiliary dune. GPR data was collected using a 200 MHz antenna with a continuous scan method and was processed by removing direct arrival, gain balancing, migration and more which produced the highest resolution imagery from this region to date. Large dune data was analyzed to determine depositional process for different sedimentary patterns observed. Auxiliary dune data was analyzed to determine dune type and migration direction. Our results indicate five sedimentary process zones in the near surface of the large primary dune. These processes include motion of the dune crest as well as different phases of superimposed dune deposition. It is evident from our interpretation that there have been at least two phases of superimposed dune deposition separated by an erosional process boundary. These phases of deposition have produced a reversed succession of strata on opposing sides of the dune with deposits of 3D superimposed dunes beneath 2D superimposed dune deposits on the west and deposits of 2D superimposed dunes beneath 3D superimposed dune deposits on the east. This suggests a reversal of wind environment in the region in the recent past and could provide insight into the building and stability of linear dunes on Earth. Our results also indicate that the auxiliary study dune is oblique in nature with migration to the north-northeast and that it and other similar dunes in the vicinity are formed because of their proximity to Tsondab Vlei. The apparent dependence of these smaller scale features on interruptions in the dunefield like Tsondab Vlei suggest that the normal wind patterns within the dunefield are a combination of the regional wind patterns with significant influence from the large linear dunes themselves.

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Much research has been done to study the effects of spacing in laterally loaded pile groups and how the pile spacing affects lateral resistance of the piles. In this test a 9-pile group of steel piles was installed in a 3x3 configuration in sand. The piles were spaced from center-to-center at a distance of 5.65 pile diameters in the direction of the load. The pile group was laterally loaded and instrumented to collect deflection, load, and strain data. A separate single pile was similarly instrumented and tested for comparison to the pile group. The soil profile consisted of a top layer of sand about 2.5 meters deep underlain by alternating layers of fine grained soil and sand. Analysis was done in order to determine p-multipliers for the rows in the pile group. The pile group consistently resisted lower average loads than those of the single pile at the same peak deflection. Row 1 resisted equal loads to those resisted by the single pile but Row 2 and Row 3 resisted smaller loads successively. The maximum bending moments were greatest in Row 1 and decreased successively in Row 2 and Row 3, however they occurred at the same depth for the same peak deflection. Maximum bending moments for the single pile were similar to those for Row 1 in the pile group at each deflection. Group effects were more significant at greater loads with larger deflections. Higher deflection caused increased shear zone interaction and a decrease in lateral resistance. The test on the single pile was modeled using the computer program LPILE Plus version 4.0 (Reese et al., 2000). The soil profile was calibrated by alternating the input soil parameters until the curves matched between the measured and the calculated results. The new soil profile was then used to model the test on the pile group using GROUP version 4.0 (Reese and Wang, 1996). A match was made between the measured test results and those calculated using GROUP by defining p-multipliers for each of the rows. For Cycle 1 the p-multipliers were found to be 1.0, .55, and .5 for Row 1 through Row 3 respectively. For Cycle 10 the p-multipliers were found to be the same as those for Cycle 1.

This dissertation focuses on relating spaceborne microwave data to the geophysical characteristics of the Sahara desert and the Amazon vegetation. Radar and radiometric responses of the Saharan ergs are related to geophysical properties of sand formations and near surface winds. The spatial and temporal variability of the Amazon vegetation is studied using multi-frequency and multi-polarization data. The Sahara desert includes large expanses of sand dunes called ergs that are constantly reshaped by prevailing winds. Radar backscatter measurements observed at various incidence and azimuth angles from the NASA Scatterometer (NSCAT), the ERS scatterometer (ESCAT), the SeaWinds scatterometer aboard QuikScat (QSCAT), and the Precipitation Radar (TRMM-PR) aboard the Tropical Rain Monitoring Mission (TRMM) are used to model the backscatter response from sand dunes. Backscatter incidence and azimuth angle variation depends upon the slopes and orientations of the dune slopes. Sand dunes are modeled as a composite of tilted rough facets, which are characterized by a probability distribution of tilt. The small ripples are modeled as cosinusoidal surface waves that contribute to the return signal at Bragg angles. The backscatter response is high at look angles equal to the mean tilts of the rough facets and is lower elsewhere. The modeled backscatter response is similar to NSCAT and ESCAT observations. Backscatter also varies spatially and reflects the spatial inhomogeneity of the sand surface. A model incorporating the backscatter azimuth modulation and spatial inhomogeneity is proposed. The maxima of the azimuth modulation at 33 degrees incidence angle reflect the orientation of the slip-sides on the sand surface. These slip-side orientations are consistent with the European Centre for Medium-Range Weather Forecasts wind directions spatially and temporally. Radiometric emissions from the ergs have strong dependence on the surface geometry. The radiometric temperature (Tb) of ergs is modeled as the weighted sum of the Tb from all the composite tilted rough facets. The dual polarization Tb measurements at 19 GHz and 37 GHz from the Special Sensor Microwave Imager (SSM/I) aboard the Defense Meteorological Satellite Program and the Tropical Rainfall Measuring Mission Microwave Imager are used to analyze the radiometric response of erg surfaces and compared to the model results. It is found that longitudinal and transverse dune fields are differentiable based on their polarization difference azimuth modulation, which reflects type and orientation of dune facets. Polarization difference at 19 GHz and 37 GHz provide consistent results. In the Amazon, backscatter measurements from Seasat A scatterometer (SASS), ESCAT, NSCAT, QSCAT and TRMM-PR; and Tb measurements from SSM/I are used to study the multi-spectral microwave response of vegetation. Backscatter versus incidence angle signatures of data combined from scatterometers and the precipitation radar depend upon vegetation density. The multi-frequency signatures of backscatter and Tb provide unique responses for different vegetation densities. Backscatter and Tb spatial inhomogeneity is related to spatial geophysical characteristics. Temporal variability of the Amazon basin is studied using C-band ERS data and a Ku-band time series formed by SASS, NSCAT and QSCAT data. Although the central Amazon forest represents an area of very stable radar backscatter measurements, portions of the southern region exhibit backscatter changes over the past two decades.

Pile caps are used in foundation design to aid multiple single piles to act as a pile group to resist lateral forces that may cause overturning moments. The pile cap and pile group resist these forces by pile-soil-pile interaction, base and side friction along the pile cap-backfill interface, and passive earth resistance. Passive earth resistance has been neglected in design due to a limited amount of full-scale testing. This research presents the results of a combination of hydraulic actuator and eccentric-mass shaker full-scale testing of a pile cap with loose silty sand backfill to quantify the contribution of the passive earth resistance to the lateral force resistance. The test cap is 1.12 m tall and 5.18 x 3.05 m in plan view, connecting 12 steel pipe piles (324mm O.D) placed in a 4 x 3 pattern with center-to-center spacing of 4.4 and 3.3 pile-diameters in the long and short dimensions, respectively. The hydraulic actuator applied a static load to the system (backfill + pile group) while the eccentric-mass shaker introduced cyclic and dynamic loading to the system. The passive earth resistance accounted for approximately 22% of the total system resistance, with piles contributing approximately 78%. Furthermore, the results produce general correlations between cyclic and dynamic effects on degradation of the backfill provided by the testing and soil characteristics obtained, including target (static) displacement, dynamic displacement amplitude, stiffness, and damping. The dynamic displacement amplitudes during the eccentric mass shaker tests typically ranged between .4 and 2 mm for frequencies between 5 and 9.5 Hz representing behavior under reloading conditions rather than virgin loading conditions. Generally, the presence of the loose silty sand backfill nearly doubled the dynamic stiffness of the pile cap. The stiffness of the backfill and pile cap combined was typically between 100 and 200 kN/mm for frequencies between 4 and 8 Hz, while the stiffness for the backfill alone was typically a decreasing trend between 100 and 40 kN/mm for the same frequency range. The overall isolated loose silty sand damping ratio shows a general increasing trend with values from 32% to 55% for frequencies 3 and 8 Hz.