Thesis (M.M. (Public Policy))--University of the Witwatersrand, Faculty of Commerce, Law and Management, Graduate School of Public and Development Management, 2013. / The foremost argument of this research is that the quality of matric learner performance in mathematics and science is poor. The objective of the research is to investigate the factors leading to poor performance in mathematics and science at matric level in Gauteng, South Africa. The research seeks to validate whether or not decision-making, policy and planning contribute to poor learner performance. Five documents addressing mathematics and science education matters were analyzed. Six candidates were interviewed to determine the causes of poor performance in mathematics and science at matric level in Gauteng and how the quality of learner performance could be improved. The findings confirmed that the quality of passes in mathematics and science is indeed poor and showed that the National Policy on Promotion and Progression Requirements Grades R-12 in particular contributes to this poor quality of learner performance. They also confirmed that poor decision-making at strategic level and poor planning are also contributors towards poor learner performance. Scenario planning, as a strategizing foresight tool, was employed to create the Gauteng scenarios for mathematics and science education in 2022. A recommendation is made that the GDE should use these scenarios as learning tools when preparing for the future and to improve their planning and decision-making processes.

O conhecimento dos processos que envolvem o movimento da água no solo e de fundamental importância para o manejo e a conservação do solo e da água. Ha situações em que, durante um evento de chuva intensa, a água se move mais rapidamente no perfil através de canais, sem que haja interação com a matriz do solo; esse movimento e chamado de fluxo preferencial. Atualmente e aceita em estudos de campo a existência deste fluxo preferencial em uma ampla variedade de solos. No entanto, muitos métodos utilizados para determiná-lo diretamente alteram o fluxo da água através da matriz do solo, processo de drenagem de relevância indiscutível nos solos. Em trabalho recente realizado no Japão, esse problema foi superado com sucesso pela aplicação concomitante, durante e um pouco após os eventos de chuva, da equação de Darcy-Buckingham e do método do balanço de água no solo: a equação de Darcy-Buckingham infere sobre a presença de fluxo preferencial da água, definido, nessa abordagem, como o resíduo da equação do balanço de água no solo durante os eventos de chuva. Este método apresenta, portanto, a grande vantagem de tornar possível a determinação experimental do fluxo preferencial a uma dada profundidade do solo, em condições de campo, sem interromper significativamente o fluxo mátrico de água. O objetivo deste trabalho foi a determinação e caracterização do fluxo preferencial da água nas profundidades correspondentes aos horizontes B textural e B latossólico de um Nitossolo Vermelho eutrófico em condições de campo, aplicando a equação de Darcy-Buckingham e o método do balanço de água no solo, durante e um pouco após os eventos de chuva. Devido ao baixo volume de chuva durante a última estação chuvosa, em apenas duas situações foi possível reconhecer uma alteração significativa na umidade do solo em profundidades superiores a 0,5m e nas duas situações foi verificada fluxo preferencial no horizonte Bt, não foi verificado fluxo preferencial no horizonte Bw durante os eventos chuvosos avaliados. A metodologia utilizada foi eficiente na observação de fluxos de água no solo que não são influenciados pela matriz. / The understanding of the processes involving soil water movement is essential to soil and water management and conservation. There are situations in which the water moves faster in the soil profile through channels, during an event of intense rain, without interacting with soil matrix; this movement is known as preferential flow. Currently, it is accepted in field studies the existence of preferential flow in a wide range of soils. Nevertheless, many methods used to directly determine it change the water flow through the soil matrix, a drainage process of unquestionable relevance in soils. In a recent study carried out in Japan, this problem has been successfully overcome by simultaneously applying Darcy-Buckingham\'s equation and the soil water balance method during and shortly after rain events; the Darcy-Buckingham\'s equation infers on the presence of preferential water flow, defined in this approach as the residue of the soil water balance equation during the rain events. Therefore, this method has the great advantage of making possible the experimental determination of the preferential flow at a certain depth in soil, in field conditions, without significantly interrupting matric water flow. This study aimed to determine and characterize preferential water flow in depths corresponding to textural and latosolic B horizons of a Eutrophic Red Nitosol in field conditions, applying Darcy-Buckingham\'s equation and the soil water balance method, during and shortly after rain events. Due to the low volume of rain in the last rainy season, a significant change in soil moisture below 0.5 m was only observed in two situations, where preferential flow in Bt horizon was also verified. Preferential flow was not verified in the Bw horizon during the analyzed rain events. The methodology used was efficient in the observation of soil water flows not influenced by the soil matrix.

O conhecimento dos processos que envolvem o movimento da água no solo e de fundamental importância para o manejo e a conservação do solo e da água. Ha situações em que, durante um evento de chuva intensa, a água se move mais rapidamente no perfil através de canais, sem que haja interação com a matriz do solo; esse movimento e chamado de fluxo preferencial. Atualmente e aceita em estudos de campo a existência deste fluxo preferencial em uma ampla variedade de solos. No entanto, muitos métodos utilizados para determiná-lo diretamente alteram o fluxo da água através da matriz do solo, processo de drenagem de relevância indiscutível nos solos. Em trabalho recente realizado no Japão, esse problema foi superado com sucesso pela aplicação concomitante, durante e um pouco após os eventos de chuva, da equação de Darcy-Buckingham e do método do balanço de água no solo: a equação de Darcy-Buckingham infere sobre a presença de fluxo preferencial da água, definido, nessa abordagem, como o resíduo da equação do balanço de água no solo durante os eventos de chuva. Este método apresenta, portanto, a grande vantagem de tornar possível a determinação experimental do fluxo preferencial a uma dada profundidade do solo, em condições de campo, sem interromper significativamente o fluxo mátrico de água. O objetivo deste trabalho foi a determinação e caracterização do fluxo preferencial da água nas profundidades correspondentes aos horizontes B textural e B latossólico de um Nitossolo Vermelho eutrófico em condições de campo, aplicando a equação de Darcy-Buckingham e o método do balanço de água no solo, durante e um pouco após os eventos de chuva. Devido ao baixo volume de chuva durante a última estação chuvosa, em apenas duas situações foi possível reconhecer uma alteração significativa na umidade do solo em profundidades superiores a 0,5m e nas duas situações foi verificada fluxo preferencial no horizonte Bt, não foi verificado fluxo preferencial no horizonte Bw durante os eventos chuvosos avaliados. A metodologia utilizada foi eficiente na observação de fluxos de água no solo que não são influenciados pela matriz. / The understanding of the processes involving soil water movement is essential to soil and water management and conservation. There are situations in which the water moves faster in the soil profile through channels, during an event of intense rain, without interacting with soil matrix; this movement is known as preferential flow. Currently, it is accepted in field studies the existence of preferential flow in a wide range of soils. Nevertheless, many methods used to directly determine it change the water flow through the soil matrix, a drainage process of unquestionable relevance in soils. In a recent study carried out in Japan, this problem has been successfully overcome by simultaneously applying Darcy-Buckingham\'s equation and the soil water balance method during and shortly after rain events; the Darcy-Buckingham\'s equation infers on the presence of preferential water flow, defined in this approach as the residue of the soil water balance equation during the rain events. Therefore, this method has the great advantage of making possible the experimental determination of the preferential flow at a certain depth in soil, in field conditions, without significantly interrupting matric water flow. This study aimed to determine and characterize preferential water flow in depths corresponding to textural and latosolic B horizons of a Eutrophic Red Nitosol in field conditions, applying Darcy-Buckingham\'s equation and the soil water balance method, during and shortly after rain events. Due to the low volume of rain in the last rainy season, a significant change in soil moisture below 0.5 m was only observed in two situations, where preferential flow in Bt horizon was also verified. Preferential flow was not verified in the Bw horizon during the analyzed rain events. The methodology used was efficient in the observation of soil water flows not influenced by the soil matrix.

The influence of bulk density on saturated, unsaturated hydraulic conductivity , diffusivity and water con tent was measured on undisturbed and disturbed soil samples of Vernal sandy loam and Nibley silty clay loam. Bulk density was changed by artificially compacting the samples. There was a very large decrease in hydraulic conductivity and diffusivity as water content decreased as has been noted by many others . For the disturbed and compacted samples of the Vernal sandy loam, the water content was higher at .33 and 1.0 bar suction than for the disturbed- uncompacted samples. The same general effect was noted for the undisturbed samples, but differences due to treatment were small . The reverse was true at .05 bars. In the Nibley silty clay loam samples , water content was higher for the uncompacted than for the compacted samples at all suctions applied. The effect of compaction on unsaturated hydraulic conductivity and diffusivity was not consistent. At the same value of water content , both diffusivity and unsatura ted hydraulic conductivity were sometimes higher in the compacted samples, others lower than in the uncompacted.

The performance of Thin Membrane Surface (TMS) highways is largely controlled by the strength of the subgrade soil which in turn is a function of the soil suction (Fredlund and Morgenstern, 1977). Thermal conductivity suction sensors can be used to indirectly measure in situ matric suction. <p>Thirty two (32) thermal conductivity sensors were installed under Thin Membrane Surface (TMS) in two highway locations; namely, Bethune and Torquay, Saskatchewan, in September 2000. The sensors were installed beneath the pavement, shoulder and side-slope to monitor matric suction and temperature changes with time. The monitoring system at Bethune was damaged after two years of operation. The thermal conductivity sensors at Torquay all appear to have been working well and data are still being collected.<p>Other attempts had been made in the past to use thermal conductivity sensors for field suction measurement, but all were terminated within a short period of time due to limitations associated with the equipment. The long-term suction measurement at the Torquay site is unique and provides valuable field data. <p>This research project presents and interprets the long-term matric suction measurements made between the years 2000 to 2005 at the Torquay site and from 2000 to 2002 at the Bethune site. To help in the interpretation of the data, a site investigation was undertaken along with a laboratory testing program that included the measurement of Soil-Water Characteristic Curves (SWCC). As well, a limited laboratory study was undertaken on several new thermal conductivity matric suction sensors. <p>The matric suction readings in the field showed a direct relationship to rainfall and regional evaporation conditions at the test sites. At the Bethune and Torquay test sites, the changes in matric suctions appeared to be mainly due to the movement of moisture through the edge of the road. Relatively constant equilibrium suctions were encountered under the driving-lanes. Conversely, matric suctions under the side-slopes were found to vary considerably with time and depth. Matric suctions under the driving-lanes ranged from 20 to 60 kPa throughout the years. Matric suctions on the side-slopes changed from 100 to 1500 kPa over the years. <p>The greatest variation of soil suctions occurred in the month of April from location to location in the subgrade. The soil suctions became less variable in June while larger variations again occurred from July to October. <p>The matric suction measurements obtained from the thermal conductivity sensors showed a general agreement with the values estimated using the soil-water characteristic curves, SWCC, measured in the laboratory.

The performance of Thin Membrane Surface (TMS) highways is largely controlled by the strength of the subgrade soil which in turn is a function of the soil suction (Fredlund and Morgenstern, 1977). Thermal conductivity suction sensors can be used to indirectly measure in situ matric suction. <p>Thirty two (32) thermal conductivity sensors were installed under Thin Membrane Surface (TMS) in two highway locations; namely, Bethune and Torquay, Saskatchewan, in September 2000. The sensors were installed beneath the pavement, shoulder and side-slope to monitor matric suction and temperature changes with time. The monitoring system at Bethune was damaged after two years of operation. The thermal conductivity sensors at Torquay all appear to have been working well and data are still being collected.<p>Other attempts had been made in the past to use thermal conductivity sensors for field suction measurement, but all were terminated within a short period of time due to limitations associated with the equipment. The long-term suction measurement at the Torquay site is unique and provides valuable field data. <p>This research project presents and interprets the long-term matric suction measurements made between the years 2000 to 2005 at the Torquay site and from 2000 to 2002 at the Bethune site. To help in the interpretation of the data, a site investigation was undertaken along with a laboratory testing program that included the measurement of Soil-Water Characteristic Curves (SWCC). As well, a limited laboratory study was undertaken on several new thermal conductivity matric suction sensors. <p>The matric suction readings in the field showed a direct relationship to rainfall and regional evaporation conditions at the test sites. At the Bethune and Torquay test sites, the changes in matric suctions appeared to be mainly due to the movement of moisture through the edge of the road. Relatively constant equilibrium suctions were encountered under the driving-lanes. Conversely, matric suctions under the side-slopes were found to vary considerably with time and depth. Matric suctions under the driving-lanes ranged from 20 to 60 kPa throughout the years. Matric suctions on the side-slopes changed from 100 to 1500 kPa over the years. <p>The greatest variation of soil suctions occurred in the month of April from location to location in the subgrade. The soil suctions became less variable in June while larger variations again occurred from July to October. <p>The matric suction measurements obtained from the thermal conductivity sensors showed a general agreement with the values estimated using the soil-water characteristic curves, SWCC, measured in the laboratory.

In many situations, the upper layers of soil above the ground water table are in a state of unsaturated condition. Although unsaturated soils are found throughout the world, they are predominant in arid or semi-arid regions. In these areas, the soil water characteristic curve (SWCC) which relates the water content to the matric suction could be used as key tool to implement the mechanics of unsaturated soils into the designs of geotechnical structures such as dams, embankments, pavements, canals, and foundations. Several experimental techniques are available for determining the SWCC in a laboratory environment. However, these experimental techniques are expensive, time consuming typically requiring days or weeks, depending on the soil type, and demanding intricate testing equipment. Due to these reasons, there has been a growing interest to find other means for estimating SWCC and encourage the adoption of unsaturated soils mechanics in geotechnical engineering practice. Several methods exist to indirectly estimate the SWCC from basic soil properties. Some may include statistical estimation of the water content at selected matric suction values, correlation of soil properties with the fitting parameters of an analytical equation that represents the SWCC, estimation of the SWCC using a physics-based conceptual model, and artificial intelligence methods such as neural networks or genetic programming. However, many studies have shown that environmental effects such as temperature, soil structure, initial water content, void ratio, stress history, compaction method, etc. can also affect the SWCC. This means that the estimation SWCC from set of conditions may not reliably predict the SWCC in other conditions. Due to this reason, it is crucial for engineers involved with unsaturated soils to take into account all the factors that influence the SWCC. The two key objectives of the present thesis are the development of a method based on first principles, using the capillary rise theory, to predict the variation of the SWCC as a function of temperature, as well as developing a technique for the prediction of the fixed parameters of a well-known function representing the SWCC based on basic soil properties together with the moisture profile of a soil column subjected to a known temperature gradient. A rational approach using capillary rise theory and the effect of temperature on surface tension and liquid density is developed to study the relation between temperature and the parameters of the Fredlund and Xing (1994) equation. Several tests, using a Tempe cell submerged in a controlled temperature bath, were performed to determine the SWCC of two coarse-grained soils at different temperatures. A good comparison between the predicted SWCC at different temperatures using the proposed model and the measured values from the Tempe cell test results is achieved. Within the scope of this thesis, a separate testing program was undertaken to indirectly estimate the SWCC of the same two coarse-grained soils from the measurement of their steady state soil-moisture profile while subjected to a fixed temperature differences. The water potential equation in the liquid and vapor phases is used to analyses the steady state flow conditions in the unsaturated soil. A good comparison is obtained for the SWCC estimated using this technique with the SWCC measured used a Tempe cell submerged in a controlled temperature bath. The results of this study indicate that knowledge of the moisture content of a soil specimen under a constant thermal gradient and basic soil properties can be used to estimate the SWCC of the soil at the desired temperature.

Tez (Yüksek Lisans) - Süleyman Demirel Üniversitesi, Fen Bilimleri Enstitüsü, İnşaat Mühendisliği Anabilim Dalı, 2008. / Bibliyografya var.

abstract: Design and mitigation of infrastructure on expansive soils requires an understanding of unsaturated soil mechanics and consideration of two stress variables (net normal stress and matric suction). Although numerous breakthroughs have allowed geotechnical engineers to study expansive soil response to varying suction-based stress scenarios (i.e. partial wetting), such studies are not practical on typical projects due to the difficulties and duration needed for equilibration associated with the necessary laboratory testing. The current practice encompasses saturated “conventional” soil mechanics testing, with the implementation of numerous empirical correlations and approximations to obtain an estimate of true field response. However, it has been observed that full wetting rarely occurs in the field, leading to an over-conservatism within a given design when partial wetting conditions are ignored. Many researchers have sought to improve ways of estimation of soil heave/shrinkage through intense studies of the suction-based response of reconstituted clay soils. However, the natural behavior of an undisturbed clay soil sample tends to differ significantly from a remolded sample of the same material. In this study, laboratory techniques for the determination of soil suction were evaluated, a methodology for determination of the in-situ matric suction of a soil specimen was explored, and the mechanical response to changes in matric suction of natural clay specimens were measured. Suction-controlled laboratory oedometer devices were used to impose partial wetting conditions, similar to those experienced in a natural setting. The undisturbed natural soils tested in the study were obtained from Denver, CO and San Antonio, TX. Key differences between the soil water characteristic curves of the undisturbed specimen test compared to the conventional reconstituted specimen test are highlighted. The Perko et al. (2000) and the PTI (2008) methods for estimating the relationship between volume and changes in matric suction (i.e. suction compression index) were evaluated by comparison to the directly measured values. Lastly, the directly measured partial wetting swell strain was compared to the fully saturated, one-dimensional, oedometer test (ASTM D4546) and the Surrogate Path Method (Singhal, 2010) to evaluate the estimation of partial wetting heave. / Dissertation/Thesis / Masters Thesis Engineering 2017

Doctorat en sciences appliquées / info:eu-repo/semantics/nonPublished