No description available.

Suspended solids, turbidity and discharge data for thirty-seven reservoir releases, three major periods of dam overspill, and 20 unregulated tributary flood events, on seven different river systems, are analysed in order to examine suspended solids transport dynamics within regulated rivers and to assess the effectiveness of reservoir releases material. Within Great Britain, two sudden releases of water to the in removing within-channel accumulations of out of every five major reservoirs cause regulated river. Reservoir releases also provide, with their fixed and constant discharges, a unique opportunity to undertake field experiments investigating the importance of channel suspended solids sources, suspended solids supply limitation, the nature of the suspended solids load on turbidity and flow routing within upland boulder bed channels. The reservoir release suspended solids loads relate to sediment source depletion and changing sources along the channel. Close to the· dam, suspended loads are usually small with fine organic matter dominating the seston, which. scanning electron microscopy revealed to be predominantly autochthonous organic matter, with algal fragments derived from extensive and ·rapid periphyton growth within the regulated rivers. Downstream, minerogenic particles dominate the seston. This represents the flushing of channel bed accumulations derived from· unregulated tributaries. Seasonal variation in the nature of the suspended solids loads is also revealed. The quantity of material transported relates to the relationship between reservoir release or dam overspill frequency and that of unregulated tributary flood events. Marked hysteresis between suspended solids transport and discharge was characteristic on all the regulated rivers. In addition, hysteresis in the relationship between turbidity and suspended solids concentrations was also apparent, this relating to spatial and temporal changes in seston composition. Finally, the results obtained allow not only the nature of suspended solids transport within regulated rivers to be described and the effectiveness of reservoir releases for flushing in-channel accumulations of material to be ascertained but also the formulation of management guidelines and recommendations. These guidelines relate to effective environmental management of regulated river habitats in rivers experiencing reservoir releases.

This document reviews the scour protection systems required around port structures where these are to be used for the berthing of vessels powered by water jet systems. The development of a scour protection system at Poole Harbour in Dorset has been documented and reviewed and a series of laboratory investigations were then undertaken. This has enabled a greater understanding of the scour mechanisms from the water jet propulsion systems of High Speed Ships. This work has shown that current design guidance on scour protection is not appropriate for use on berths used by High Speed Ships, that failure of these systems can occur rapidly and catastrophically, and secondary effects from water jets may promote the failure of quay walls. The scour protection system should comprise two individual elements, a filter layer and an armour layer. It has been found that systems involving individual isolated armour units are inappropriate and prone to failure and that shaped linked armour blocks need to be used. The loads on the armour layer were also found to be oscillatory and the materials used for both the armour and filter layers need to be designed for cyclic fatigue loading and fretting. Water jets are also capable of reducing the strength of permeable, seabed strata.

In the last 50 years there have been many documented failures of gravity retaining quay walls due to earthquake events. These failures are often associated with significant deformation of liquefiable soil deposits (e. g. major damage occurred at Kobe Port during the 1995 Hyogoken-Nanbu earthquake). Saudi Arabia has similar types of quay walls located in regions that have the potential to experience significant seismic events. These walls have not been designed for seismic resistance and therefore have the potential to suffer serious damage from seismic activity. For many years the design of seismic gravity quay walls has been studied and design codes for engineering practice established; however, the widespread failures of these structures during recent earthquakes demonstrates that these design methods may be insufficient. Such gravity quay wall failures have stimulated progress in the development of a performance-based seismic design method using non-linear inelastic dynamic analysis for quay wall structures. The aim of this study was to develop a methodology for the seismic design of gravity quay walls using a non-linear elasto-plastic dynamic analysis. The final method adopted in this work is based on the generalised elasto-plasiticity constitutive model developed by Pastor et aL (1990), with some minor modifications, which has been incorporated into a finite element procedure. The proposed P-Z sand model was first validated by simulating published monotonic and cyclic test results. Secondly, an effective stress analysis was established by developing a finite element model for Kobe Port Island quay walls using the P-Z sand model. This model was validated by comparing the predicted deformations with those experienced at Kobe. The computed residual deformations from the analysis were in good agreement with published field observations. To develop mitigation strategies, a parametric study of the seismic perfonnance of gravity quay walls, using the effective stress analysis, was conducted. This study assessed the effect of various structural and geotechnical parameters on the seismic performance of quay walls. Twenty-six cases of effective stress analysis with variation in tidal range, soil permeability, soil relative densities, and wall widths were conducted as well as analyses to test the importance of considering multi-directional seismic excitations as opposed to uni-directional. In order to assess the safety of existing quay walls in Jeddah Port, an experimental programme was conducted. This programme consisted of a site investigation (using a standard penetration test (SPT)) to determine the in situ relative density of the existing backfill, a series of laboratory based, monotonic and cyclic triaxial tests (to define the soil properties of Jeddah Port sand) and a two-dimensional effective stress finite element analysis of a typical Jeddah quay wall. The monotonic and cyclic triaxial tests were conducted for three different relative densities of D, = 35 %, 55% and 75%. These represent loose (equal to in situ conditions as established by the site investigation), medium dense and dense sand. The experimental results are discussed and then used to identify the P-Z sand model parameters. These parameters were used in conjunction with a finite element analysis of Jeddah Port quay walls to Predict the seismic deformations. In this analysis the finite element model was subjected to a number of different ground motions, which represented two different levels of earthquake intensity; namely moderate and strong ground shaking. The effect of improvement strategies such as increasing the relative density of the backfill and foundation materials was then assessed The results of the simulations showed that existing Jeddah Port quay walls are not satisfactory to resist either moderate or strong earthquake excitations. However, if the relative density is increased to 55% then satisfactory performance can be achieved for a moderate intensity earthquake. For the case of strong shaking, the analysis showed that the quay walls did not demonstrate the required performance levels; however, they were only under specification by 10%. Finally, a flowchart illustrating a seismic design procedure for gravity quay walls has been proposed, which is applicable to both existing and new gravity quay walls. Key-words: quay wall, liquefaction, earthquake, port, effective stress, constitutive model.

The aim of this thesis is to investigate how the time-dependent behaviour of flood defence properties can be appropriately characterised and incorporated in a reliabilitybased approach. Such an approach is required in a maintenance optimisation framework for flood defence management. The first objective shows that existing structural reliability methods are suitable for the analysis and incorporation of asset time-dependent processes in flood defence (system) reliability. Recent progress on quantitative maintenance optimisation frameworks for flood defence management is drawn together and complemented by theory from other engineering disciplines. The second objective develops three importance measure types to indicate the relevance of the time-dependent processes in the context of a rational maintenance optimisation approach. These importance measures support practical operational management as well as maintenance optimisation model design. The third objective develops a modelling methodology to describe asset time-dependent processes of flood defences by a statistical model. The first phase in the modelling methodology is problem formulation. The second conceptualisation phase is a five-step analysis of the asset time-dependent process. Firstly, existing field observations and scientific understanding are assembled. Secondly, the excitation, ancillary and affected features and uncertainty types of the asset time-dependent process are analysed. The third step describes the character of the process conditional on the excitation. The fourth step analyses the dependencies between different asset time-dependent processes. The fifth step formulates alternative statistical models for the asset time-dependent process. The last phase in the modelling methodology is parameter estimation, calibration and model corroboration. Historical observations on asset time-dependent processes are scarce and can either be used for further extension of this phase or Bayesian posterior updating. The fourth objective demonstrates the methods developed in this thesis in a (system) reliability model of the Dartford Creek to Swanscombe Marshes flood defence system along the Thames Estuary.

Three experimental marine epoxy coatings on steel substrates were tested under four-point bend cyclic-loading in both simulated sea water, at two temperatures, and in air. Freshly prepared and artificially aged coatings were examined. The samples were characterised by sectioning, scanning electron microscopy and EDX elemental analysis. The ageing processes used had multiple stages involving temperature cycles and/or repeated water soaking and drying. The coatings were loaded at strain amplitudes of 0.15% and 0.22% for 500,000 cycles at frequencies simulating wave action. The coatings showed high fatigue resistance, so slot defects of different depths and widths were introduced to simulate damage in service and to act as crack initiators. This permitted observation of crack propagation under cyclic loading. Additionally, plastic substrates were tried so that tests at higher coating strains of 1.33% could be performed. The results showed that the softest epoxy coating was the most fatigue resistant. An epoxy containing large filler particles (50gm diameter) was the next most resistant while a hard epoxy with small filler particles showed multiple fatigue cracking after 300,000 cycles when tested on steel substrates. No fatigue cracks were observed on aged coatings. Internal stress measurements were performed that showed the coating which was most resistant to fatigue had the lowest internal stress of around 2 MPa. The other coatings internal stress levels were over 15 MPa. Tensile tests on free-films indicated that the coating most resistant to fatigue showed the lowest tensile strength, approximately 10 MPa, and the highest strain to failure, the latter property being the more important one. Hardness measurements using micro and macro Vickers indentors were performed between stages of an ageing process, along with nano-indentation (to measure Young's modulus) showing that the softest coating exhibited low elasticity. Higher hardness values were observed for coatings after ageing.

A detailed study has been made of the oxygen transfer resulting from the air entrained into a free water recipient by water jets. Particular attention has been paid to various free falling jets entering a pool for a variety of conditions of this pool, also to a guided jet terminating in the formation of an hydraulic jump. These features are common to a number of hydraulic structures. An extensive laboratory programme has been conducted, the effect of all important hydraulic variables has been investigated together with water quality effects, in particular the effect of dissolved salts. Dimensionless correlation equations have been developed and some success has been achieved in determining the modelling laws governing the oxygen transfer in an air entrainment situation. Modelling according to the Froude law of similarity has shown that the oxygen transfer expressed as a deficit ratio varied as a simplified function of the scale. For the first time, the laboratory measurements of oxygen transfer due to a free falling jet entering a free water recipient have been successfully correlated with data received for a number of prototype dam and weir structures. Similar success has been achieved in correlation with published laboratory work on free overfall weirs, and a wider range of applicability to multi crested and cascade weirs has been shown subject to certain conditions.

No description available.

No description available.

There is evidence that hydrologic systems exhibit memory processes that may be represented by fractional order systems. A new theory is developed in this work that generalises the classical unit hydrograph technique for the rainfall-runoff transformation. The theory is based upon a fractional order linear deterministic systems approach subject to an initial condition and is taken to apply to the entire rainfallstreamflow transformation (i.e. including baseflow). The general equation for a cascade of time-lagged linear reservoirs of fractional order subject to a constant initialisation function is derived, and is shown to be a form of fractional relaxation model. Dooge's (1959) general theory of the instantaneous unit hydrograph is shown to fit within the new theoretical framework. Similarly the relationship to the general storage equation of Chow and Kulandaiswamy (1971) is demonstrated. It is shown that the correct initialisation of cascade models requires a substantial number of initial conditions which may limit the viability of applying them in practice. Consequently, the differential formulation of the classical Nash cascade has been corrected and reinterpreted. The unbounded nature of the solution to the convolution integral form of the single fractional relaxation model is overcome by application of the Laplace transform of the pulse rainfall hyetograph following Wang and Wu (1983). The model parameters are fitted using the genetic algorithm. The fractional order cascade equations are tested for classical rainfall-runoff modelling using a set of 22 events for the River Nenagh. The cascade of 2 unequal fractionalorder reservoirs is shown to converge to that of the integer order case, whilst the cascade of equal reservoirs shows some differences. For the modelling of the total rainfall-streamflow process the single fractional order reservoir model with a constant initialisation function is tested on a selection of events for a range of UK catchment scales (22km^ to 510km ). A rainfall loss model is incorporated to account for infiltration and evapotranspiration. The results show that the new approach is viable for modelling the rainfall-streamflow transformation at the lumped catchment scale, although the parameter values are not constant for a given catchment. Further work is recommended on determining the nature of the initialisation function using field studies to improve the identification of the model parameters on an event-by-event basis.