Geotechnical and hydrogeological characterization of residual soils in the vadose zone

Groundwater is an important natural resource and ought to be protected. Groundwater recharge and contamination are two important aspects in groundwater management. Both these aspects apply to the vadose zone. The research aimed to narrow the knowledge gap between practising geohydrologists and engineering geologists, both frequently involved in vadose zone investigations for geohydrological and engineering purposes respectively. The vadose zone is the portion of the geological profile above the groundwater surface and is usually characterised by unsaturated conditions. Matrix forces counteract the force of gravitation to hold liquid in the porous medium and are reflected by hydraulic heads lower than atmospheric pressure (suction). The unique relationship between soil-water content and suction is presented by soil-water characteristic curves. Flow of liquids is directly proportional to the hydraulic gradient and the hydraulic conductivity and is affected by the geometric properties of the pore channels. In unsaturated soils, flow is governed by both matrix and gravitational forces. Preferential flow is the process by which water and solutes move along preferred pathways through a porous medium. Important hydrogeological properties, such as porosity, hydraulic conductivity and soil-water retention characteristics, can be estimated from geotechnical data. Unsaturated hydraulic conductivity can also be estimated from soil-water characteristic curves and saturated hydraulic conductivity. The experimental procedures comprised analyses of existing hydrogeological data, laboratory tests and field experiments. The geotechnical data were used to predict important hydrogeological properties and these predictions were compared to experimentally derived hydrogeological properties. The effects of preferential flow and soil variability were also investigated. Predictions of porosity, hydraulic conductivity and soil-water retention characteristics lack precision, owing mostly to the natural variability in hydrogeological properties and inherent errors of the empirical models. Accurate predictions of unsaturated hydraulic conductivity were based on experimentally derived saturated hydraulic conductivity and soil water characteristic data. The study area is located in Midrand and is underlain by granitoid rocks that had been subjected to a number of geomorphologic events. The land system classification approach was used to delineate the hydrogeological units. The different hydrogeological characteristics can be attributed mainly to the position of the hydrogeological units in respect of the topographical setting, the geomorphologic history and the underlying geology. A conceptual hydrogeological model was constructed for each of the hydrogeological zones and its significance in respect of groundwater recharge and vulnerability discussed. The research has shown that geohydrological properties can be estimated from geotechnical data with various degrees of accuracy. Predictions of hydraulic conductivity, soil water retention characteristics and porosity are not suitable for site-specific investigations, but it can be used during the feasibility phases. In cases where saturated hydraulic conductivity and soil-water retention characteristics have been experimentally derived, estimations of unsaturated hydraulic conductivity are adequate for site-specific investigations. The land system approach can be used to delineate areas of similar geohydrological characteristics and these can be used in the compilation of aquifer vulnerability and groundwater recharge maps.Thesis (PhD)--University of Pretoria, 2006.GeologyUnrestricte

A New Residual Monte Carlo Method for Estimating Errors in Deterministic Transport Solutions

The residual Monte Carlo (RMC) method is also known in the literature as sequential Monte Carlo and reduced-source Monte Carlo. Given a Monte Carlo method for solving a linear equation and an approximate solution to that system, the residual method enables use of essentially the same Monte Carlo algorithm to directly compute the additive error or “defect” associated with the approximate solution. As the size of the defect decreases relative to the size of the solution, the residual Monte Carlo method becomes increasingly efficient relative to the standard Monte Carlo (SMC) method. Here we present a new RMC algorithm for evaluating the space-angle error in Discrete Ordinates radiation transport solutions, and provide computational examples demonstrating that it can be far more efficient than SMC for this purpose

Die gebruik van die Sjinese Graskarp (Tenopharyngodon idella (Val.) in die beheer van die onderwatermakrofiet Potamogeton pectinatus L. in Germistonmeer

M.Sc.Please refer to full text to view abstrac

An analysis of the electro discharge machining process through remote monitoring

M.Ing.The Electro Discharge Machining (EDM) process is a machining process that is widespread, and a constant search for further optimisation thereof exists. Additionally, the need for remote monitoring and control of such systems is prominent in industry, as automisation lends itself to the control of groups of machinery from a central location. This thesis presents a remote monitoring system, equipped with an Expert System in the pursuit of optimising the efficiency of an EDM system. Extensive test results are used to build the rule base for the Expert System. Experimental results confirm optimisation of efficiency, and the experimental setup is illustrated

Four contexts of action research: Crossing boundaries for productive interplay

This paper explores how action research takes place within and between four contexts: adding practical value, improving institutions, developing professions, and contributing to theory. We argue that action research is more than those activities conducted within these contexts: it is a process of handling the generative tensions in the boundary regions. Framing action research this way has proven helpful in recasting such tensions as meaningful, in thinking through research designs in teaching and practice, and in paying sufficient attention to boundary work. This model for conceptualising action research has been refined over two decades of practice and reflection by the authors

Continuous performance improvement in the South African National Defence Force

This article concentrates on the South African National Defence Force (SANDF), as a South African public sector department, its acceptance of the Batho Pele principles and the implementation of various organisational performance improvement programmes. However, despite accepting the principles and the programmes, it is uncertain whether the SANDF institutionalised them in order to effect continuous performance improvement

Single Particle Microelectrodes for Electrochemical Analysis of Sulfide Flotation Processes

The true electrochemical characteristics of sulfides found in industrial processes are of interest and as a result a relatively simple technique has been developed to study fundamental electrochemical interactions of individual particles measuring less than 100 microns in diameter. Cyclic voltammetry with sulphide mineral microelectrodes has been carried out on sulphide particles hand-picked from the concentrate and tailings products of an auriferous sulfide ore floated in air and nitrogen. These particles were found to be exclusively pyrite for the +53 micron fraction. Experimental results show no prominent differences in the electrochemical response of these pyrite particles from different flotation products but it appears that particle shape effects can contribute to pyrite losses in the tailings product

Leiderschap in leren: Inzichten vanuit leervoorkeuren geven leiders handvatten voor effectiever lerende organisaties

Waarom zouden we een artikel willen schrijven over leiderschap en leren, wetende dat juist het gesprek over leren bij veel leiders aversie oproept. Maar… als je constateert dat 80 procent van al het leren in de praktijk plaatsvindt (infor-meel), en slechts 20 procent in trainingen en opleidingen (formeel) (Doornbos, 2006; Cross, 2006), is dat dan niet reden genoeg om deze handschoen op te pakken? Wij dachten van wel! Het uitgangspunt van dit hoofdstuk is dat leiding-geven aan leren en ontwikkelen een centrale taak van de leider is. Leiderschap in leren heeft een belangrijke en onderschatte rol. Onbewuste opvattingen en beperkt inzicht in het eigen leren, maar ook in het leren en ont-wikkelen van medewerkers, team en organisatie staan het effectief vormgeven hieraan in de weg. 'Ze snappen het gewoon niet', 'Ze zijn te bang', 'Ze blijven hangen', 'Ze zoeken onnodig naar zekerheid', 'Ze blijven maar vragen om stu-ring' zijn opmerkingen die lucht geven aan de irritatie die vaak veroorzaakt wordt door verschillen met de eigen manier van leren en ontwikkelen. In dit hoofdstuk leggen we verbindingen tussen leren en leiderschap en onderzoeken we implicaties voor het leidinggeven aan organisaties. We verken-nen de breedte van het leren en bespreken vijf toepassingsniveaus van sturing geven aan leren, om vervolgens per niveau voorstellen te doen voor leiders om met leren en diversiteit in leren om te gaan. 8.1 Wat is leiderschap en wat heeft dat met leren te maken? Lerende organisaties vragen om een nieuwe visie op leiderschap. De traditionele opvatting waarin 'bijzondere mensen de richting bepalen, de belangrijke beslis-singen nemen en de troepen inspireren', werkt niet meer, aldus Senge (1990). Ongeacht of je de lerende organisatie blijft zien als wenkend perspectief of als tijdelijke hype, het leren in en van organisaties blijft onverminderd een vraag-stuk in het centrum van organisatieontwikkeling, en wint daar zelfs exponen-tieel aan belang! Dat traditionele vormen van opleiden en formeel leren ontoereikend zijn om hieraan ten volle vorm te geven, is duidelijk (Schön, 1987; Cross, 2006). De aandacht is inmiddels gevestigd op het informele en collectieve leren. De nood-12

Remote monitoring of a tailings dam using the Internet of Things

Due to their size and often their remoteness, large geotechnical structures such as tailings dams are ideally suited to be observed using smart monitoring technologies. With the arrival of the 4th Industrial Revolution – and in a year characterised by unprecedented disruption and uncertainty impacting physical access for monitoring purposes – adoption of state-of-the-art Internet of Things (IoT) solutions for remote monitoring applications provides a unique, real-time view into the behaviour of these structures. To improve understanding of the long-term pore pressure behaviour associated with the operation of a tailings dam, the Department of Civil Engineering at the University of Pretoria (UP), in collaboration with SRK Consulting and Marula Platinum, is conducting an instrumentation project to observe pore pressure (both positive and negative), moisture content and temperature at nine monitoring locations on a platinum tailings dam. The Marula Platinum Mine is situated approximately 30 km northwest of the town of Burgersfort. The mine operates a tailings dam with a footprint of 48 Ha on which deposition occurs by means of spigotting.https://journals.co.za/journal/civenghj2021Civil Engineerin