Extremely huge quantities of mined ore materials are processed annually to obtain the various types of minerals being the barebones of industry. Impounding the waste materials (tailings) of the mined minerals behind a raised embankment is the major and most common method used for the disposal of theses materials. Due to its execution simplicity and low cost, the upstream raising method has been the most common method used for retaining the disposed tailings in spite of being the most failure-vulnerable one. The sophisticated hydromechanocal behavior of the upstream tailings disposal facilities (UTDFs) during the staged construction makes the traditional approaches of consolidation, stability, and seepage analyses inefficient for producing accurate and, in many situations, correct design and evaluation of the UTDFs. The major objective of this thesis is to propose a thorough procedure for realistically evaluating the hydromechanical response of the UTDFs during their staged construction. The procedure incorporates a numerical model that reflects the combination of important realistic features of the UTDFs, namely (i) the partially saturated flow characteristics under the transient state dominating the facility throughout its operation/construction life; (ii) the two dimensional consolidation response of the facility components under both the partially and fully saturated cases considering (a) the full coupled response between the fluid and the solid phases and (b) the large deformation-nature of the tailings; as well as (iii) the appropriate mechanical behavior of the facility materials including a model that can detect the inception of liquefaction in the liquefaction-susceptible zones of the facility. The influences of a number of operational/construction measures that have been reportedly critical for the stability of the UTDFs are investigated in the light of the proposed model. Moreover, the inappropriateness of the traditional approaches for realistically evaluating the UTDF hydromechanical response during its staged construction is substantiated in the analyses carried out in this work. / The conclusions and recommendations drawn from this thesis are paramount not only for the feasibility, preliminary design and risk assessment studies of the UTDF during its operation/construction life but also for the on going analytical investigations and monitoring/instrumentations plans carried out throughout such life.

No description available.

The residual flow procedure (RFP) is used to conjunction with finite element method for solution of steady state free surface seepage in dams containing open cracks. The cracks are simulated using the thin-layer element concept. A comprehensive parametric study is performed to analyze the applicability of the numerical procedure with the thin layer element. Here, vertically trending as well as horizontally trending open cracks are considered with variable lengths, widths, and conductivities. It is found that the numerical results involve oscillatory, unstable, and physically unreasonable behavior beyond critical values of the geometry and conductivities. Here, the vertically trending configurations are found to be relatively more sensitive than the horizontally trending configurations. Although additional research will be needed to analyze other factors such as different crack geometries, transient flow, and different ratios of crack conductivities to surrounding soil conductivities, the results presented here suggest that the procedure can be applied for seepage analysis in dams containing open cracks.

A dissertation submitted to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, Johannesburg, in fulfilment of requirements for the degree of Master of Science in Engineering Johannesburg, 2017 / South Africa is a water scarce country and dams play a large role in the infrastructure of our country by providing water for many purposes. With the growth of the country, new dams are needed and existing dams require rehabilitation. Often, increasing a spillways capacity forms part of the rehabilitation required at dams. Therefore, one of the main aims of this study is to look at an option for increasing a spillways discharge capacity. The labyrinth and Piano key weirs (PKW) were investigated together with a combination of the two spillway types. Different geometric attributes were combined and varied to develop a new design that would assist in improving discharge capacity while reducing the cost, producing an economically viable option. Thirty five physical models were built and tested in this regard. Comparison was made with the standard PKW design in terms of discharge capacity, hydraulic efficiency, length ratio (L/W) and cost related to concrete volume required. It was concluded that efficiency, discharge capacity and cost can be improved with this new combined design however more geometric variations need to be studied to ascertain these results. / MT 2018

Dams are among the most critical of civil engineering structures and are susceptible to damage due to seepage. Geomembranes have been used to minimize seepage problems in dams since 1959. However, geomembranes are vulnerable to damage, in the form of tears and punctures, during installation and throughout the service life. These defects impact the effectiveness of a geomembrane as an infiltration barrier resulting in leakage through the geomembrane liner and into the body of the dam. The majority of previous studies conducted to investigate leakage through defects in geomembranes considered heads below 0.3 m, which corresponds to flow for conditions experienced by landfill liners. The main objectives of this study were to quantify the leakage rate through defects in geomembrane lining systems for dam and to evaluate the implications of the leakage on the performance of dams. Experimental, analytical and numerical studies were conducted as part of this investigation. The experimental testing program included permeameter cell tests for the following lining systems: i) geomembranes over clay layers, ii) geomembranes over sand layers and iii) geomembranes over geosynthetic clay liners. The permeameter tests were conducted to investigate the effects of soil type, initial water content, dry unit weight and hydraulic head on leakage through a defect in a geomembrane liner. The analytical component was conducted to evaluate the transmissivity at the interface and radius of wetted area for the tests conducted as part of the experimental component. The numerical component of this study was performed using the finite element method to simulate the experimental tests and the performance of actual dams. Ultimately, the laboratory tests and subsequent analyses were used to develop a set of tools (e.g., empirical models, design recommendations) that are expected to assist engineers in the design of geomembrane lining systems for dams. Also, the study was used to identify and address potential concerns (e.g., global stability) that may result in failure of systems in which geomembrane liners are used. This study is expected to contribute to a better understanding of the performance of geomembranes as dam liners. The presence of a geomembrane, even with a defect, was found to reduce the amount of leakage that occurs through a soil layer. New predictive equations were developed to estimate leakage through defects in composite lining systems. The finite element analyses indicated that a dam with a geomembrane with very large defects would not develop pore pressures that were similar to those observed for an unlined dam. The factor of safety for the unlined dam was improved by the placement of a geomembrane on the upstream face. Consequently, a geomembrane may also eliminate the need for a blanket drain at the downstream toe, which could decrease the cost of construction. / text

Please read the abstract in the section 00front of this document / Thesis (PhD (Civil Engineering))--University of Pretoria, 2007. / Civil Engineering / unrestricted

Inflatable dams are flexible membrane structures, pressurized with either air, water, or both, which have been used in recent years as a means of temporarily impounding water. A number of procedures have been developed to investigate the static behavior of the dams, but the dynamic behavior has been largely neglected. The few studies that have been done on dynamic behavior have used the simplifying assumption that the weight of the membrane was negligible. In this study, equations of equilibrium and equations of motion were derived for an air inflated dam impounding no water, but loaded with its own membrane weight. It was assumed that the effect of membrane extensibility is negligible in the analysis. Derivatives required in the equations of motion were approximated using finite difference equations. Computer programs were written to find solutions for the eigenvalues and eigenvectors of the equations of motion. The computer program plotted the mode shapes of vibration associated with the four lowest eigenvalues, as well as the static shape of the dam. The eigenvalues obtained were the square of the frequencies of the system, so the effects of a series of membrane weights on the frequencies of dams of various base lengths could be analyzed. / M.S.

This study proposes the use of a pipe line system to transport the inflow sediment to a reservoir through the dam, and discharge it downstream. The system is powered by the available head at the dam. It aims at restoring the original sediment transport regime of the river (i.e. before the dam was built). The idea is fundamentally sound because of the much more efficient sediment transport characteristics of pipes compared to that of open channels. The necessary theory for the hydraulic design of such a system was simply not available and is developed in this study. The work of numerous previous investigators is summarized in the final results and in the developed equation which allows for the calculation of the capacity transport concentration of sediments in pipes. This equation, coupled with the most accepted head loss equation, and the continuity principle, allows for the hydraulic design of systems transporting grannular material. The calculation procedures were fitted into computer programs. In addition to computer programs, design charts where developed which allow for quick application as well as visualization of the developed concepts. It was concluded that the proposed system is fundamentally feasible. Although no economic analysis was conducted, indicators show that it is also economically favorable.

The relationship between Man and Nature can be divided into three ‘eras.’ The first era refers to a time when Man was dominated by Nature, governed by her fluctuating seasons and at the mercy of her erratic moods. Man’s advancement brought into being the Machine, which enabled Man to move into a second era. This era brought about a brief state of equilibrium between Nature and Man, before Man advanced even further and faster into a third era in which Man and Machine dominated Nature. Man’s appropriation of Nature’s resources is his most intimate experience of the Natural world. However, in this third phase of development, Man has negated the ‘natural’ source of Nature’s resources and has thus disconnected himself from her. As a result of this disconnection, the third era is characterised by an imbalance which is leading towards the possibility of Man tipping off the scales entirely. This thesis explores the possibility of a fourth era in which Man and Nature once again achieve an equilibrium of mutually beneficial symbiosis. A fourth era would be the setting of a mend in the severed Man-Nature relationship. A ‘reconnection’ could be achieved through a renewed understanding of the systems, both natural and technological, that supply Man with Nature’s resources. The ‘Machine’ that is the Vaal Dam Wall and its surrounds was chosen as a locus for the theoretical application of a form of inhabited resource infrastructure that takes steps towards a fused Man-Nature entity. The dam wall is a significant piece of existing infrastructure that plays a major role in the capture, storage, and distribution of water to people in Gauteng, South Africa’s economic powerhouse. A legible, multi-use intervention sensitively placed on this site could reconnect the water-users to the natural water resource that is so vital to their livelihoods. The intervention is in the form of a visitor centre which incorporates water purification and hydroelectric power generation as well as a management facility for the Department of Water Affairs, the entity with jurisdiction over the Vaal water system and dam wall site. The Vaal Dam Visitor Centre could provide much-needed infrastructure to the chosen site in its un-realised capacity as a locus for tourism, education, research and management. In doing so, the Centre could be the ‘Machine’ that reconnects Man to Nature through responsible use and understanding of her resources.

The intention of this work is to provide a deeper understanding of the engineering geological behaviour of granite saprolite and how this affects the engineering of such material, with specific reference to the construction of Injaka Dam in the north eastern portion of South Africa Whilst extensive investigation of weathered granites has been carried out internationally, very little detailed research on the nature of this material is documented locally. The construction of Injaka Dam afforded the opportunity to investigate the saprolite in detail. This study was initially submitted to the Department of Geology and Applied Geology at the University of Natal, Durban (renamed the University of KwaZulu-Natal in 2004) to fulfill the requirement of a Master of Science degree in 200 I. Following this submission, and supported by recommendations made by the external examiners and the project supervisor, it was agreed to upgrade the work and submit this thesis for the degree of Doctor of Philosophy. Intensive chemical weathering of granite at Injaka Dam site has resulted in the formation of thick saprolitic deposits overlying the weathered bedrock. The granite forms part of the 3 075 Ma Nelspruit Suite which has been intersected by the African erosion surface. The extensive, multicyclic period of weathering and erosion that formed this surface has resulted in deep (up to 35 m) chemical weathering of the underlying bedrock in this area. The construction of Injaka Dam on this material necessitated a thorough engineering geological investigation to understand the nature of the weathering and the possible influences it exerts on the engineering behaviour of the saprolite. This was accomplished by analysing the weathering of the granite and relating the effects of these weathering processes and changes to the engineering behaviour of the material. By applying various chemical and mineralogical indices to the weathered granite, the intensity of weathering and related changes could be quantified and compared with the engineering behaviour of the material. This was achieved by applying a series of engineering indices to the material and relating these to the quantified weathering changes. In this way tentative extrapolation of the engineering behaviour of the material could be gained and used to predict engineering performance. The resultant effects of the engineering behaviour of the material on the design and construction of the dam are also discussed. / Thesis (Ph.D.)-University of KwaZulu- Natal, 2004.