Some of the largest and deepest mines in the world are situated in South Africa. Underground temperatures and humidity can be controlled by means of complex chilled water reticulation system. A cascade pumping system is used to pump the used water from the underground levels back to the surface. The dewatering process is energy intensive. Large volumes of water are used during the general mine drilling periods (06:00 to 12:00). During blasting periods (15:00 to 18:00) a minimum amount of personnel are underground, yet large volumes of water are still sent underground due to a lack of control. Reducing the water sent underground, will reduce the amount of water pumped back to the surface; resulting in significant energy savings. Water flow and pressure can be managed by installing control valves at appropriate positions throughout the water reticulation system. Selecting a control valve is typically governed by constraints such as cavitation, water hammer, flashing, safety ratings and control range. A basic set of calculations can be used to determine whether a valve conforms to a specific scenario. However, scenarios calculated by engineers are not indicative of all applied system scenarios. When control valves are installed, to optimise the operation of a system, it affects the system’s characteristics. Sampled system data will therefore no longer provide adequate readings to help with selecting the correct control valve. An analytical control valve selection method has been developed and implemented. The case study shows the results and practical implications of applying this method in the mining industry. Implementing the analytical valve selection method is shown to be viable, realising electrical energy cost savings for the mine by reducing power requirements from Eskom. Analytical control valve selection for mine water reticulation systems / Thesis (MIng (Mechanical Engineering))--North-West University, Potchefstroom Campus, 2013.

Some of the largest and deepest mines in the world are situated in South Africa. Underground temperatures and humidity can be controlled by means of complex chilled water reticulation system. A cascade pumping system is used to pump the used water from the underground levels back to the surface. The dewatering process is energy intensive. Large volumes of water are used during the general mine drilling periods (06:00 to 12:00). During blasting periods (15:00 to 18:00) a minimum amount of personnel are underground, yet large volumes of water are still sent underground due to a lack of control. Reducing the water sent underground, will reduce the amount of water pumped back to the surface; resulting in significant energy savings. Water flow and pressure can be managed by installing control valves at appropriate positions throughout the water reticulation system. Selecting a control valve is typically governed by constraints such as cavitation, water hammer, flashing, safety ratings and control range. A basic set of calculations can be used to determine whether a valve conforms to a specific scenario. However, scenarios calculated by engineers are not indicative of all applied system scenarios. When control valves are installed, to optimise the operation of a system, it affects the system’s characteristics. Sampled system data will therefore no longer provide adequate readings to help with selecting the correct control valve. An analytical control valve selection method has been developed and implemented. The case study shows the results and practical implications of applying this method in the mining industry. Implementing the analytical valve selection method is shown to be viable, realising electrical energy cost savings for the mine by reducing power requirements from Eskom. Analytical control valve selection for mine water reticulation systems / Thesis (MIng (Mechanical Engineering))--North-West University, Potchefstroom Campus, 2013.

Thesis (Ph.D.(International Politics))-University of Pretoria, 2004. / Summaries in English and Afrikaans. Includes bibliographical references.

abstract: This study presents the results of one of the first attempts to characterize the pore water pressure response of soils subjected to traffic loading under saturated and unsaturated conditions. It is widely known that pore water pressure develops within the soil pores as a response to external stimulus. Also, it has been recognized that the development of pores water pressure contributes to the degradation of the resilient modulus of unbound materials. In the last decades several efforts have been directed to model the effect of air and water pore pressures upon resilient modulus. However, none of them consider dynamic variations in pressures but rather are based on equilibrium values corresponding to initial conditions. The measurement of this response is challenging especially in soils under unsaturated conditions. Models are needed not only to overcome testing limitations but also to understand the dynamic behavior of internal pore pressures that under critical conditions may even lead to failure. A testing program was conducted to characterize the pore water pressure response of a low plasticity fine clayey sand subjected to dynamic loading. The bulk stress, initial matric suction and dwelling time parameters were controlled and their effects were analyzed. The results were used to attempt models capable of predicting the accumulated excess pore pressure at any given time during the traffic loading and unloading phases. Important findings regarding the influence of the controlled variables challenge common beliefs. The accumulated excess pore water pressure was found to be higher for unsaturated soil specimens than for saturated soil specimens. The maximum pore water pressure always increased when the high bulk stress level was applied. Higher dwelling time was found to decelerate the accumulation of pore water pressure. In addition, it was found that the higher the dwelling time, the lower the maximum pore water pressure. It was concluded that upon further research, the proposed models may become a powerful tool not only to overcome testing limitations but also to enhance current design practices and to prevent soil failure due to excessive development of pore water pressure. / Dissertation/Thesis / Ph.D. Civil and Environmental Engineering 2011

As the energy efficiency of dishwashers continuously improves, differentmanufacturers need to find new innovative solutions to further improve thedishwashers. To do so one can divide the areas of improvement into 4 parameters,water temperature, washing time, chemical treatment and mechanical processing.In this thesis the focus lies on the mechanical processing and the washing time. The conventional spray arm of today's dishwashers sets its rotational velocitythrough the water pressure. To step away from this ASKO Appliances AB hasdeveloped a prototype with a motorized lower spray arm. The purpose of this studyis therefore to investigate how the motorized spray arm performs in terms of energyusage, wash results and sound. This when altering the factors water pressure,rotational velocity and washing time. To get reliable results with the least amount of tests, the methodology of Design ofExperiments was used through the software MODDE 7. A 3-level full factorialdesign was chosen. The three factors were varied in three levels -1, 0, 1 and fiveextra centerpoints were added resulting in a test schedule of 32 tests. To measurethe wash result a soiling method and an evaluation method was developed. Theresults of the executed test schedule was analysed through MODDEs in-builtregression model Multiple Linear Regression. The analysed test results showed that the wash time was the dominant factor forboth energy usage and wash result and the second most dominant factor was waterpressure. The rotational velocity had little to no effect on the energy usage and asmall effect on the wash result at a low water pressure but increasing effect for ahigher water pressure. The measured sound values were constant over time andincreased with both increased water pressure and rotational velocity. The optimalrunning conditions regarding wash result was investigated using MODDE and thentested. The optimal rotational velocity was the setting 1, the highest level, for allthree time settings. The optimal water pressure was in the mid to high region, andincreased with increasing wash time. The results from the three optimum tests for the prototype were then compared totests with a conventional dishwasher with a pressure driven spray arm. Theconventional dishwasher was runned with its normal running conditions for thethree different time settings. The prototype achieved a similar wash result as theconventional machine for the time setting -1 but slightly better for the time setting0 and 1. The energy usage for the prototype was a doubling of the conventionalmachines energy usage. The sound measurements were excluded due to muffelingdifferences between the machines

京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第20920号 / 理博第4372号 / 新制||理||1627(附属図書館) / 京都大学大学院理学研究科地球惑星科学専攻 / (主査)教授 松浦 純生, 教授 林 愛明, 准教授 松四 雄騎 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DGAM

The stability of natural slopes is goverened by many factors, one of which is the porewater pressure. In this study, a sensitivity analysis has been conducted in GeostudioSLOPE/W to investigate the impact of near-surface pore water pressure on thefactor of safety i silt slopes. The study includes five slopes along Ångermanälven,Sweden, which previously have been investigated within the framework of a slopefailure risk mapping of the area conducted by the Swedish Geotechnical Institute,SGI. The near-surface pore water pressure in the slopes has not successfullybeen measured in this area as the slopes are very high and steep. Calculations ofslope stability done previously by Tyréns instead assumed 1) that the pore waterpressure is zero 1m in from the slope face and 2) that it decreases hydrostatically(10 kPa/m) towards the slope face, and these are the parameters studied in thesensitivity analysis. When the pore water pressure is set to zero at the surface, thefactor of safety is reduced by an average of 7 %. Setting the pore water pressure tozero 2mfrom the surace increases the safety factor by 3%on average. A lower thanhydrostatic (7 kPa/m) pore pressure gradient increases the safety factor by on average2 %. A higher than hydrostatic pore water gradient decreases the safety factorby 16% on average. The results verifies that an increase in near-surface pore waterpressure gives a lower factor of safety and decrease in near-surface pore waterpressure leads to a higher factor of safety. The slopes are generally more sensitiveto destabilizing changes of the near-surface pore water pressure than of those stabilizing.Other factors such as vegetation, cohesion, dilatancy and erosion are notconsidered in this study but likely have a considerable effect on the stability. Whenmodelling the influence of near-surface pore water pressure and other parameters,it is recommended to use a FEM program.

The effects of repeated loading on a normally consolidated,saturated silty clay, are compared to the effects of sustained loading and standard strength tests on the same material. Attention is given to axial strains and pore water pressures generated under the different loading conditions. / Thesis / Master of Engineering (ME)

Abstract Excess pore water pressure can be generated in subgrades of both railway and pavement sub-structures under cyclic loading caused by heavy traffic. When saturated subgrades are subjected to cyclic loading, excess pore water pressures accumulate over time which then could lead to migration of particles into overlying layers. The migration of subgrade soil particles to the upper layers would lead to clogging of pores and reducing the upper layers' drainage capacity. Both excess pore water pressure accumulation and migration of fine particles could negatively affect the long-term performance and service life of the sub-structures and eventually may lead to failure. Understanding the mechanism of both excess pore water pressure and migration of fine particles under cyclic loading is, therefore, essential for not only designing but also further proposing efficient and economical maintenance methods. The main objectives of this research are to (1) investigate excess pore water pressure generation in fine granular materials under cyclic loading and (2) evaluate migration of fine granular materials into overlying layers under cyclic loading.  A series of undrained cyclic triaxial tests were performed to study the excess pore water pressure generation in fine granular materials. Two types of fine granular materials, i.e., railway sand (natural granular material) and tailings (artificial granular material), were selected for this investigation. The cyclic characteristics of these materials, e.g., accumulated strain and excess pore water pressure, were evaluated in terms of number of cycles and applied cyclic stress ratios (CSR). As a result, axial strain and excess pore water pressure accumulated over time due to cyclic loading. However, its accumulations were significantly dependent on CSR values and material types. Finally, a relationship between excess pore water pressure and accumulated strain of the fine granular materials was discovered based on all outputs from the undrained cyclic triaxial tests (both tailings and railway sand samples).  In order to evaluate the migration of fine granular materials into overlying layers under cyclic loading, a modified large-scale triaxial system was used as a physical model test. Samples prepared for the modified large-scale triaxial system composed of a 60 mm thick gravel layer overlying a 120 mm thick subgrade layer (tailings and railway sand). The quantitative analysis on migration of the fine granular materials was based on the mass percentage and grain size of migrated materials collected at the gravel layer. In addition, the cyclic responses (strain and pore water pressure) were evaluated. As a result, the total migration rate of the railway sand sample was found to be small. There were no migrated sand particles pumped up to the gravel surface, i.e., no mud pumping, after the test terminated. The migrated sand particles were observed and collected at the bottom half of the gravel layer. The total migration rate of the tailing sample was much higher than that of the railway sand sample. In addition, the migration analysis revealed that finer tailings particles tended to be migrated into the upper gravel layer easier than coarser ones under cyclic loading. The migrated tailings particles were observed at the surface of the gravel layer after the test ended. It could be involved in significant increases in excess pore water pressure at the last cycles of the physical model test. The findings obtained in this research may provide an additional contribution to the literature dealing with the excess pore water pressure accumulation and its effects on the migration of fine particles under cyclic loading.

Yes / Wave-seabed-pipelines interaction is of critical importance in the design of submarine pipelines. Previous studies mainly focus on investigating the characteristics of flow fields and hydrodynamics around a single pipeline. In this study, laboratory experiments and numerical simulations have been performed to examine the effect of burial depth and space between the centers of twin pipelines on the wave-seabed-twin pipelines interaction subject to waves. In the mathematical model, the Volume-Averaged Reynolds-Averaged Navier-Stokes (VARANS) equations are used to describe the wave motion in the fluid domain, while the seabed domain is described by using the Biot's poro-elastic theory. Numerical models are validated using these experimental measurements and available relevant experimental data. Experimental and numerical results indicate that the burial depth and relative position of twin pipelines can significantly affect the wave-averaged flow velocity field and the pore-water pressure distribution as well as effective stress.