Infrastructure Engineering - Theses
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ItemRapid drawdown in earth dams( 1971)It would appear that the most rational method of obtaining the rapid drawdown pore pressure response is to apply the field stress path to laboratory samples of the embankment material. However this approach has not been very successful and stability analyses indicate that a detailed understanding of rapid drawdown response is necessary for safe and economic design. Therefore controlled drawdown tests were carried out in the laboratory and the results were compared with various methods of prediction. The drawdown behaviour could be predicted by a refined analysis but the results cannot be applied directly to field situations. The drawdown stress changes were studied for prototype structures and the variables that govern the undrained pore pressure response were also studied. On the basis of these investigations the reported field measurements can be understood and a conservative design estimate of the drawdown pore pressure response is given.
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ItemFree surface flow in a circular conduit: a theoretical and experimental investigation of the influence of velocity distributions on flow behaviour( 1963)General Introduction: Since Chezy first proposed his well known equation for uniform flow in open channels, many other formulae have been suggested, either to replace the Chezy expression or form determining the value of the coefficient C. Perhaps the major objection to the use of these formulae is that no account is taken of the variation of the boundary effects with Reynolds number — although in some cases this is done indirectly by relating Chezy’s C to the hydraulic mean radius. Following more recent work, notably by Prandtl, there have been attempts to produce relationships between Chezy’s C, Reynolds number and a roughness parameter, (similar to those which exist for pipe flow) but these habe not been generally applied as the effects of the free surface and unsymmetrical flow conditions have not yet been fully evaluated.
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ItemPneumatic separation of grain from straw and chaff in the combine harvester( 1970)The riddle mechanism, used to clean threshed grain in harvesting machinery, has remained basically unchanged for over a century. The desired function and throughput of the cleaning mechanism in a harvester is discussed, together with the effectiveness of the conventional system. The published work on a combined harvester is reviewed; the history and development of the various components leading to their present configurations is examined together with work done on developing alternatives to the usual components in a harvester. Pneumatic separation in a vertical air stream, proposed as an alternative to the riddle system of cleaning the efflux from the threshing system of a harvester, is examined in depth. Theoretical prediction of the performance of a vertical air stream, as a separator, is shown to be intractable while predictions of separation based on terminal velocities of all the types of particles present in the mixture (which were measured fully) are shown to provide only a fair indication of likely performance. A small pneumatic separator was designed and built; the performance of this unit was investigated in detail; the effects of air velocity, feed rate, and of material composition are discussed. Likely ways of improving separation, together with the lines along which further investigations should be conducted, are discussed using the results obtained from the separation tests.
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ItemA rational approach to the thermodynamic behaviour of air chambers( 1967)In the past, studies of air pockets as well as air chambers utilized the polytropic relationship; p Vn = constant, to represent the thermodynamic behaviour of the air. Since this simple equation specifies the properties of the air without regard to the accompanying physical transients, it cannot truly satisfy the thermodynamic requirements. The main aim of the present project is to indicate a rational approach which is in accordance with the condition for thermodynamic behaviour. Controlled laboratory experiments verify the general trend of the proposed theory and illustrate how erroneous the adoption of a constant value of the polytropic index, n, can be. The concept developed is further applied to a typical air chamber installation to emphasize how the pressure-volume relationships differ from other methods.
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ItemSoil moisture and hydrology of the basalt plains of Western Victoria: a field and computer study of surface hydrology( 1979)This is a field and digital model study of surface hydrology. An attempt is made to relate field measurements to the assumptions of a physically-based deterministic rainfall-runoff model that has been proposed for widespread use in Australia. A major part of the field study was the measurement and interpretation of soil moisture contents obtained with a neutron moisture meter, and two methods were developed and used to provide calibrations appropriate to both locally variable soils and the large (55 km2) study area. Independent estimates of each of the major components of the water balance were made, utilizing data collected on the study by other authorities. Further measurements of field parameters were made to provide independent estimates of the appropriate parameter values for the digital model. A single year of data was used for development of the model and final selection of the parameter values. The prediction of the observed streamflow was used as the basis for this testing, and the hydrological validity of the assumptions upon which the model is based was then tested by a comparison of the internal prediction and the independent measurements of soil moisture contents. The model was found to behave reasonably well, but deficiencies in some of the algorithms were identified. A sensitivity analysis showed that the concept of an infiltration capacity is not important for runoff generation on this catchment, and that the spatial variability of the moisture holding capacity of the soil makes it virtually impossible to estimate this model parameter from field measurements alone. It was found that a simple approximation to this spatial variability provided a more realistic annual hydrograph, and reduced the accuracy required to determine the mean value of this moisture storage capacity from field measurements. The main conclusions are that deterministic models offer a useful approach to the understanding of surface hydrology, although further development is required before the parameter values for such a model can be determined solely from field measurements. The use of the field measurements and the model showed that the hydrology of this catchment is dominated by a nearly impermeable B horizon, that the concept of an infiltration capacity is irrelevant to the generation of storm runoff, and that the spatial variation of the moisture holding capacity of the soil is important. Particular topics for further study include the acceptance of spatial variability in the other algorithms of the model, and the hydrological validation of this and other models on other catchments.
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ItemThe control of thermal and shrinkage cracking in reinforced concrete( 1977)Wide, randomly spaced cracks in lightly reinforced concrete members result from restrained reductions in the volume of the member. Extensive research in the past has identified the causes of these volume changes (e.g. thermal contraction, creep and drying shrinkage) but comparatively little research effort has been directed specifically towards controlling the cracks induced by these movements. This thesis examines the control of thermal and shrinkage cracking in reinforced concrete members. A survey of the literature discusses the causes of this type of cracking and identifies the critically important role played by the bond of reinforcing to the surrounding concrete; the majority of current crack width prediction formulae are shown to be unsatisfactory. A review follows of recent structures in which thermal and shrinkage cracks were causing concern, and indicates that present design recommendations and criteria are inadequate. Simple and comprehensive theoretical models of restrained concrete members are developed and equations are derived enabling the prediction of the behaviour of cracks. Experimental work determined the mechanisms by which different types of reinforcing act to control the width and shape of cracks in reinforced concrete walls. Amounts of conventional reinforcing up to four times greater than presently recommended values are shown to be necessary to achieve a controlled pattern of cracks, and fundamental differences identified between the control exercised by deformed bar and fabric reinforcement.
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ItemMathematical modelling for the management of waste water systems( 1978)A need is shown to exist for a general approach to the management of the wastewater system in modern cities. This system, comprising sewage treatment plant, outfalls and receiving waters proves to be complex when viewed over planning periods of fifty years or more. A general mathematical model is, therefore, described which provides a simple framework for the analysis of such systems. In general, it is seen that the mathematical model will use particular sub-models for particular investigations. The ‘output’ from the model is a 'cost effectiveness' curve which is an intelligible presentation of the costs of the "best" options and their effects on water quality. Decision making is seen to be a political task, the costs and effects of which can be made clearer to the public, too, by moans of the cost-effectiveness curve. A case study is presented concerning the major sewage treatment system of Melbourne, Australia. This system discharges its effluent into Port Phillip Bay, which in the main, does not suffer from pollution problems at present. The model proposed for Port Phillip Bay comprises two models - a water quality model and an optimization model. The water quality model itself comprises three sub-models, a hydrodynamic model, a transport model and a model of phytoplankton growth. The hydrodynamic model is based on the two dimensional finite difference scheme proposed by Leendertse (1967) and provides information on depth integrated velocities and water levels. These are used, in turn, by a Lagrangian transport model in which the dispersion of a patch of pollutant is simulated by a cloud of computational particles. The transport information determined by this model is then passed on to a model of phytoplankton growth in the Bay. This model takes into account the effects of the nutrients of nitrogen and phosphorous forms and also the predation of zooplankton.
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ItemStress distribution in discontinuous media( 1967)The determination of the stress distribution within a semi infinite medium, which in fact is an infinitely redundant structure, becomes complex when all the relevant factors such as material characteristics, discontinuity patterns, loading conditions and boundary restraints are considered. This complexity is further accentuated when the material has a non-linear stress-strain relationship and a condition of residual stresses associated with the insitu state. Hence as an initial study the blocks making up the semi infinite medium are considered as homogeneous, isotropic and linear elastic. In this particular study, boundary tractions represented in the form of model foundations are applied to a semi infinite medium of uniform characteristics. That is Young's modulus and Poisson's ratio are constant and the discontinuities are controlled in a horizontal and vertical direction. The stresses within the models are determined by applying photoelastic techniques. Analytical and numerical solutions are developed so as to compare results with those obtained experimentally and subsequently define behaviour patterns. Stress distributions at the contact zone between the foundation and subgrade are also studied. The subgrade is initially studied with no side restraint, however in the latter models a side restraint is applied. Studies on an opening in a discontinuous semi infinite subgrade with surface loading are also made. The relatively low stress fields set up in the subgrade require a much more sensitive photoelastic material than is generally encountered. This sensitivity however, should not be acquired at the expense of reducing Young’s modulus. A material meeting this requirement is Araldite D, with an appropriate hardener. The use of this material however requires the development of careful and precise casting techniques. These techniques are fully covered in the thesis presented. To corroborate the experimental findings with an analytical theory which to date is incompletely defined, a review of the fundamentals controlling the stress distribution is essential. The usual requirement of satisfying compatability of strain at the interface is not always satisfied. This appears to affect the stress-strain relationship, in both a micro and macro scale, and hence the stress distribution and redistribution. Four numerical methods of obtaining an approximate solution to a required degree of accuracy are presented and compared with the experimental work. 1) Finite difference approach. 2) Finite element method. 3) Boundary Singular Integral solution. 4) Energy principle approach. It is concluded that the energy principle offers the most promising approach of determining the stress distribution in a nonlinear elastic-plastic semi infinite discontinuous subgrade. Finally the possibilities of failure conditions within the rock being initiated by environmental changes such as surface loads, excavations and tunnelling are considered.
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ItemA sediment-routing model for alluvial streams( 1978)Using the complete one-dimensional equations of momentum and continuity of fluid-flow, the one-dimensional equation of sediment continuity and several appropriate transport relations, a computer simulation model is derived which is capable of routing flow and sediment through a channel reach with a moveable bed and irregular boundaries. Sediment is assumed to be transported in two modes; as suspended-load and as bed-load. The bed-load transport rate is assumed to react instantaneously to local alterations in flow conditions, while the suspended-load is assumed to take a finite time to react to local flow changes. For non-uniform bed-sediments, the total contribution to erosion or deposition at each computational point in the channel is obtained by summing the individual bed-elevation changes arising from changes in the bed-load and suspended-load for each size fraction. Flow conditions computed by the flood-routing component are then adjusted to allow for erosion or deposition before computations proceed to the next time increment. The concept of erosion probabilities, introduced by Einstein (1950) is used, along with implicit allowance for the occurrence of bed-forms on the stream bed. Several examples of model performance are presented, in which the effects of several significant parameters are demonstrated.