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Significant attempts have been made by large contractors in the UK construction industry to improve safety on their sites. Safety management systems have been put in place, minimum training requirements have been established, and worker engagement initiatives implemented in the quest for a positive safety culture. However accidents and incidents still occur. Grounded in social constructionism, this study sought to explore how people construct safety in and through their interactions at work on the large construction sites of the UK. Data was collected from five UK construction projects, all over £20m in value, and included site safety signage, conversations discussing safety and various safety documents. Discourse analysis of the data revealed considerable variation in the contextual constructions of safety. Safety was found to be inconsistent, incomplete and incidental, relating to a variety of different realities in a variety of different contexts. Relatively straightforward constructs and discourses developed around safety, such as its polarisation, the construction of safety as PPE itself, and the development of safety as un-safety. However these were further developed by more complicated and interrelated discourses of safety as practice, enforcement and engagement. The variation within and between these master discourses has consequences for safety culture in terms of its construction, homogenisation and perpetuation on sites. The study makes recommendations for further academic research to examine the variation in the discourses of safety within the management hierarchy, who seek to develop a safe work environment through the safety culture programmes yet are challenged by the conflicts of safety as engagement and safety as enforcement. The study also suggests industry interventions to facilitate the improvement and development of practices to assist safety management on large UK construction sites.

Technological advances in computer science, namely cloud computing and data mining, are reshaping the way the world looks at data. Data are becoming the drivers of discoveries and strategic developments. In environmental sciences, for instance, big volumes of information are produced by monitoring networks, satellites and model simulations and are processed to uncover hidden patterns, correlations and trends to, ultimately, support policy and decision making. Hydrologists, in particular, use models to simulate river discharges and estimate the concentration of pollutants as well as the risk of floods and droughts. The very first step of any hydrological modelling exercise consists of selecting an appropriate model. However, the choice is often made by the modeller based on his/her expertise rather than on the model's suitability to reproduce the most important processes for the area under study. Since this approach defeats the ''scientific method'' for its lack of reproducibility and consistency across experts as well as locations, a shift towards a data-driven selection process is deemed necessary. This work presents the design, development and testing results of a completely novel data mining algorithm, called AMCA, able to automatically identify the most suitable model configurations for a given catchment, using minimum data requirements and an inventory of model structures. In the design phase a transdisciplinary approach was adopted, borrowing techniques from the fields of machine learning, signal processing and marketing. The algorithm was tested on the Severn at Plynlimon flume catchment, in the Plynlimon study area (Wales, UK). This area was selected because of its reliable measurements and the homogeneity of its soils and vegetation. The Framework for Understanding Structural Errors (FUSE) was used as sample model inventory, but the methodology can easily be adapted to others, including more sophisticated model structures. The model configuration problem, that the AMCA attempts to solve, can be categorised as ''fully unsupervised'' if there is no prior knowledge of interactions and relationships amongst observed data at a certain location and available model structures and parameters. Therefore, the first set of tests was run on a synthetic dataset to evaluate the algorithm's performance against known outcomes. Most of the component of the synthetic model structure were clearly identified by the AMCA, which allowed to proceed with further testing using observed data. Using real observations, the AMCA efficiently selected the most suitable model structures and, when coupled with association rule mining techniques, could also identify optimal parameter ranges. The performance of the ensemble suggested by the combination of AMCA and association rules was calibrated and validated against four widely used models (Topmodel, ARNOVIC, PRMS and Sacramento). The ensemble configuration always returned the best average efficiency, characterised by the narrowest spread and, therefore, lowest uncertainty. As final application, the full set of FUSE models was used to predict the effect of land use changes on catchment flows. The predictive uncertainty improved significantly when the prior distributions of model structures and parameters were conditioned using the AMCA approach. It was also noticed that such improvement is due to constrains applied to both model and parameter space, however the parameter space seems to contribute more. These results confirm that a considerable part of the uncertainty in prediction is due to the definition of the prior choice of the model configuration and that more objective ways to constrain the prior using formal data-driven techniques are needed. AMCA is, however, a procedure that can only be applied to gauged catchment. Future experiments could test whether AMCA configurations could be regionalised or transferred to ungauged catchments on the basis of catchment characteristics.

The stiffness of soil is an important parameter that has implications on soil-structure interaction, on the response to earthquake motion and on the response of soils to dynamic loadings. Stiffness reduces and behaves plastically at medium to high strains; however, at small-strain the stiffness has been observed to be a constant value and elastic. Small-strain stiffness governs the soil-structure interaction during construction projects and site response during dynamic loading due to earthquakes and man-made operations. Quantifying stiffness, in particular shear stiffness, at small-strain is difficult due to the effect of sample fabric on the values measured and the resolution of the testing equipment that is available. Wave propagation has been used to measure the stiffness of samples by propagating waves in different directions and in different planes. This thesis aims to examine the propagation of stress waves through a granular medium. Samples were created using the numerical discrete element method (DEM) in two- and three-dimensions. Waves, created by a point source, were propagated through the samples and this propagation was measured using micromechanical data. The speed of the propagating wave was assessed using existing techniques and novel methods developed during the research. The effect of macro-scale parameters, such as sample boundary conditions, and the effect of micro-scale parameters, such as interparticle contact laws, on sample stiffness were examined. Randomly packed samples were created with a quantifiable fabric tensor, measured using the contact force network. Wave propagation in different directions was examined to quantify the effect of inherent anisotropy on the sample stiffness. Samples were confined at anisotropic confining pressures to isolate the effect of induced anisotropy on the sample stiffness. Wave propagation results were compared with the results of small amplitude stress probes for a number of simulations and with experimental work carried out in the University of Bristol.

Centimetre-level Global Navigation Satellite System (GNSS) based positioning is increasingly relevant for a large number of applications. Currently, this level of GNSS positioning accuracy is most commonly achieved using the conventional Real Time Kinematic (cRTK) method. In order to achieve such high-accuracies with cRTK, the distance (baseline) between the user and reference station must typically be shorter than 50 km for dual-frequency GNSS receivers. To address the limitations of cRTK, the Precise Point Positioning (PPP) method, which does not require local reference networks, was developed. The principle of PPP is to model and correct error sources such as satellite orbit and clock errors using correction products and error modelling. PPP is not currently suitable for many applications, because of the long solution convergence time (from 20 to 60 min to achieve 10 cm accuracy), insufficient positioning accuracies and a lack of integrity monitoring. Current fixed ambiguity PPP methods are analysed and tested using the National Oceanic and Atmospheric Administration (NOAA) dataset in this thesis. Based on the analysis, the most reliable existing validation method has unacceptably large rate (12.7%) of incorrect ambiguity resolution. Therefore, this thesis develops an enhanced PPP method. The enhanced PPP method is based on using the enhanced ambiguity validation method (e.g. time-window based validation) and employing both GLONASS and GPS measurements to calculate a float position solution. In addition, integrity monitoring is improved in terms of failure exclusion and protection level calculation. When employing the enhanced PPP method, the rate of incorrect ambiguity resolution decreases to 5.3% and of correct ambiguity resolution increases to 82.2% when using the (NOAA) dataset. The average horizontal, vertical and 3D position errors at the initial ambiguity resolution epoch are reduced by 40.0%, 23.8% and 31.8%, respectively, compared to the most reliable existing PPP method.

The theory of buckling strength of compression members in the plastic range has been extensively studied, and numerical methods already exist which deal with such behaviour. However, there is a significant research interest in developing analytical models for the plastic buckling, largely driven by the need for simplified mechanics based design tools, but also by the desire for enhanced understanding of this complex phenomenon. A thorough investigation into the inelastic buckling of columns and plates reveals the existence of two well-known inconsistencies recognised as the 'Column Paradox' and the 'Plate Plastic Buckling Paradox'. In the current research, addressing the conceptual issues related to the plastic buckling of columns and plates, including the two associated paradoxes, has been achieved by means of development and application of analytical models that are verified against nonlinear finite element analysis. These models are based on sound principles of structural mechanics and are intended to illustrate the mechanics of the plastic buckling response of stocky columns/plates by means of a simplified analytical approach, from the point of buckling initiation and considering the post-buckling response. In these models, the Rotational Spring Analogy is used for formulating the geometric stiffness matrix, whereas the material stiffness matrix is obtained with due consideration for the spread of material plasticity. It is shown that the buckling of stocky perfect columns starts at the Engesser load while the von Karman upper limit is typically not realised due to tensile yielding at the outer fibre of the column cross-section. Furthermore, it is established that beyond a threshold level of imperfection, as evaluated directly from the developed model, the plastic post-buckling response of columns is barely affected by a further increase in the out-of-straightness. Besides identifying previous misconceptions in the research literature, the proposed analytical models for the plastic buckling of plates have proven to offer valuable insight into factors that influence the plastic buckling of stocky plates, and hence succeeded in resolving the long-standing paradox. It is the major contention of this thesis, verified through extensive studies, that the 'Plate Plastic Buckling Paradox' is resolved with the correct application of plasticity theory, considering not only the influence of initial imperfections but also the interaction between flexural and planar actions.

There has been much interest in using biochar as a low cost sorbent amendment to reduce the risk posed by contaminated sites but an understanding of biochar interactions with plants in a contaminated soil context is still in its early stages. This thesis is based on the overall hypothesis that biochar amendment would improve soil health and plant growth in addition to reducing the availability of organic and inorganic contaminants. Biochars from three different feedstocks (maize stover, olive tree pruning and pine woodchip) and coal-derived activated carbon were used in experimental studies designed to test the thesis hypothesis. Soils contaminated with copper and arsenic (Chapters 2 and 4), mercury (Chapter 3), and polycyclic aromatic hydrocarbons (Chapters 4 and 5) were used in experiments designed to investigate the different effects biochar amendment had on specific contaminant behaviour and mobility in soils. Innovative passive sampling techniques were used to monitor changes in freely dissolved concentrations of the contaminants studied. Rhizon samplers extracted porewater from soil for selected inorganic contaminant analysis while polyoxymethylene (POM) samplers were used in laboratory equilibrium tests to determine freely dissolved concentrations of organic contaminants in soil. Biochars consistently reduced plant uptake (in plant species maize and Italian ryegrass) for both organic and inorganic contaminants. Biochars had a generally beneficial effect on plant growth. Freely dissolved concentrations were reduced for inorganic contaminants copper and arsenic (with the exception of arsenic with olive tree pruning in Chapter 2). Limited to no effects on porewater concentrations were observed for mercury (Chapter 3) and organic contaminants. Activated carbon was more effective at removing organic contaminants from porewater than biochar. By defining the conditions in which sorbent amended soils successfully reduced contaminant bioavailability and improved plant growth, this thesis demonstrates how biochar may prove a valuable tool in the phytomanagement of contaminated soils.

Video cameras have been used within the structural research community for decades, particularly for assessing movement of hard to reach areas such as bridge decks and cables. Displacement measurements have correlated well with electro-mechanical sensors and demonstrated time and cost savings. The technique has not found a substantial market within t he civil engineering community, which at first glance is unexpected given the advantages reported and the proliferation of camera-based measurements in other fields. This thesis investigates the capabilities of video measurement (with particular emphasis on Imetrum), and how they fit with in Structural Monitoring. Extensive interviews and collaborative working with organisations involved in monitoring UK structures and some overseas has identified stakeholder requirements. Barriers to adoption have been identified and investigated, as well as work done to overcome them. Fundamental experimental work (mostly field based) has enabled an in depth understanding of the factors that are specific to using video based measurement systems outdoors - surface finish; size of virtual targets used by the tracking software; impact of various weather conditions and the impact of using different optics on image quality (and hence measurement resolution). Field studies and project work have been undertaken to understand the practical benefits and limitations of applying video measurement systems, including for load testing of bridges; train induced displacement of rail track systems and longer term (1 month plus) static monitoring of bridges and tunnels. This research has shown that there are areas where a video based system is a valuable addition to the toolbox of those responsible for constructing, assessing and maintaining the UKs infrastructure, particularly where access is difficult and/or absolute displacement at speeds from 1- 300Hz required. This thesis also demonstrates this in some projects that have been paid for at commercial rates by infrastructure owners, as a proof of tangible benefit.

This thesis investigates the potential use of geopolymers to encapsulate intermediate level waste (ILW), particularly Magnox swarf contaminated with Al metal and Cs/Sr-loaded clinoptilolite. Both wastes have different interactions with the encapsulation matrix. For Magnox swarf waste containing trace Al metal, the pH of the encapsulating matrix is a key factor that controls corrosion and release of hydrogen. Cs and Sr can leach from contaminated clinoptilolite into the encapsulating geopolymer and therefore the chemical interactions of these ions with the matrix have been investigated. A fundamental understanding of the geopolymer system used for encapsulation was developed. This involved investigating the influence of different precursor on the mechanical properties. It was shown showed that metakaolin based geopolymers are unstable at room temperature when in contact with an atmosphere with a low relative humidity and excessive drying shrinkage occurs. This shrinkage can be reduced by adding inert fillers which have low impact on the mortar viscosity and mechanical strength. Magnox waste and Al-metal have been encapsulated in metakaolin based geopolymers and surface interactions studied using SEM-EDX and XRD. In addition the corrosion rates were determined. Magnox swarf does not react with the geopolymers matrix, while Al-metal rapidly corrodes. However, by using a metakaolin with a low molar Si:Al ratio and controlling the molar Al:Na ratio in geopolymers the corrosion can be significantly reduced and allows encapsulation of this difficult waste stream. Surface reactions of Cs/Sr-contaminated clinoptilolite and geopolymers were also studied. Simulated wastes containing Cs+ and Sr2+ salts were mixed with geopolymers and the influence of the cations on the geopolymer microstructure and leaching were investigated. Mixing Cs/Sr-contaminated clinoptilolite with activation solution causes surface dissolution of clinoptilolite with release of Cs and Sr ions into the matrix. Leaching of Cs contaminated geopolymers showed that Cs+ ions can be immobilised at concentrations up to 10 wt%. Sr2+ reacts with the activating solution and dissolved metakaolin and is build chemically into the structure. The research has resulted in a number of key conclusions related to the stability of metakaolin derived geopolymers and their interactions with the selected wastes.

An investigation is presented into the mechanisms governing both the ageing and axial cyclic loading characteristics of displacement piles in silica sands. The thesis considers first the state–of–knowledge regarding the axial capacity of displacement piles in silica sands. Three main areas of uncertainty are identified; the stress regime setup by installation, the mechanisms of ageing that lead to capacity increases with time (set-up), and the effects of axial cyclic loading. New laboratory experiments are then described that involved tests with extensively instrumented 36mm diameter Mini-Imperial College Piles (Mini-ICP) with roughened (Rcla ~3.5μm) stainless steel shafts and 60o conical tip bases, that could measure axial loads, and interface radial and shear stresses at multiple positions along their shafts. Less extensively instrumented piles with varying diameters were also tested. Ten installations were made in the 1.2m diameter, 1.5m deep Grenoble– INP calibration chamber. Fresh pluviated sand masses were formed for each installation, which were typically instrumented with multiple commercially sourced (Kyowa and TML) miniature sensors to measure radial, vertical and circumferential stresses in the sand mass during pile installation, ageing, and axial static and cyclic loading tests. Key parameters that might affect pile behaviour were then isolated and considered in turn. The interpretation links the model tests to instrumented field studies and the ageing trends established from a field database. The model piles’ axial cyclic loading responses are analysed by developing cyclic interaction diagrams which are linked to full scale tests and laboratory experiments to identify the key mechanisms governing field cyclic behaviour. The interaction diagrams provide a straight-forward screening tool for addressing axial cyclic loading in practice. Reference is made to more elaborate procedures and to the experiments’ scope for validating numerical models.