In most situations the dominant source of noise from the railway system for conventional speeds is rolling noise. This is radiated by the wheels, the rails which dominate the important mid-frequency region between 400 and 2000 Hz, and, at low frequencies, also the sleepers. The acoustic properties of the rails, sleepers and ballast are investigated in this thesis. The sound radiation of a rail in close proximity to a ground (both rigid and absorptive) is predicted by the boundary element method (BEM) in two dimensions (2D). Results are given in terms of the radiation ratio for both vertical and lateral motion of the rail, when the effects of the acoustic boundary conditions due to the sleepers and ballast are taken into account in the numerical models. Allowance is made for the effect of wave propagation along the rail by applying a correction in the 2D modelling. The numerical predictions of the sound radiation from a rail are verified by comparison with experimental results obtained using a 1:5 scale rail model in different configurations. The sound radiation from the sleepers has been calculated using a three-dimensional boundary element model including the effect of both reflective and partially absorptive ground. When the sleeper flexibility and support stiffness are taken into account, it is found that the radiation ratio of the sleeper can be approximated by that of a rigid half-sleeper. When multiple sleepers are excited through the rail, their sound radiation is increased as they form a composite source. This effect has been calculated for cases where the sleeper is embedded in a rigid or partially absorptive ground. It is shown that it is sufficient to consider only three sleepers in determining their radiation ratio when installed in track. At low frequencies the vibration of the track is localised to the three sleepers nearest the excitation point whereas at higher frequencies the distance between the sleepers is large enough compared with the acoustic wavelength for them to be treated independently. Measurements on a 1:5 scale model railway track are used to verify the numerical predictions with good agreement being found for all configurations. Not only can ballast absorb noise to some extent due to the gaps between the ballast particles but it can also vibrate and reradiate noise during a train pass-by. Experiments have been performed using 1:5 scale ballast to investigate this. The basic properties of the ballast, as a porous material, are measured initially, in particular the flow resistivity and porosity. The modelling of the ballast absorption is then implemented based on the corresponding measured parameters and this is compared with the measured absorption. The effects of ballast absorption on the rail and sleeper radiation are also measured, and are compared with the numerical predictions. Moreover, the vibration of the ballast is obtained experimentally. The influence of the ballast vibration on the sleeper radiation is then estimated and shown to increase the noise radiation below 200 Hz. Finally, the sound radiation from the whole track is predicted, and compared with the corresponding measured results on the 1:5 scale model. The sound radiation models for the rail and the sleeper, are used with the TWINS software to give revised predictions of the track sound radiation. Prediction differences are shown between the original TWINS and the updated models.

Engineered pavements are a key part of the transport asset that includes flexible road pavements, railway formations and airport runways. Their design, construction and maintenance need to be economically and environmentally optimised, while meeting serviceability criteria over the design life of the pavement. The main serviceability criteria used for railway track design are the permanent deformation and track stiffness. Subgrade stiffness influences the design depth of ballast and compacted formation layers are used to improve stiffness and reduce stresses induced in the natural subgrade. The track stiffness also influences vehicle/track interaction and wear, energy required for movement, and ride quality. Knowledge of the stiffness is required for safe and economic design of the railway track structure. Several factors influence the stiffness or resilient modulus of compacted formation material including stress state, material type, and soil physical state (density and water content). A laboratory investigation was conducted on a representative subballast material, at a range of water contents, using a Cyclic Triaxial Apparatus and Cyclic Hollow Cylinder Apparatus to investigate these aspects. The resilient modulus of the clayey sand material reduced as the applied deviator stress increased, and increased under higher confining stresses and matric suction. It was found that the resilient modulus increased by a factor of six due to a reduction in water content, and thus the increase in matric suction. Principal stress rotation, representative of train induced stresses, reduced the measured resilient modulus by approximately 13% for optimum water content specimens with reducing influence for dry of optimum specimens. The results from this work emphasise the benefit of matric suction, and thus the need for well drained formation layers. They also highlight the risk of reduced stiffness and increased deformation of railway formation subject to long periods of rainfall or wetting and the potential impact of predicted climate change. Simplified stress path testing using a Cyclic Triaxial Apparatus overestimates resilient modulus, especially for saturated material subject to large number of cycles. However, the use of more advanced testing of the resilient modulus using the Cyclic Hollow Cylinder Apparatus is only suggested where high cyclic shear stresses are expected.

The need for the research project is driven by the Crossrail project in London for which new 7 m diameter tunnels are to be constructed close to numerous existing operational tunnels of the London Underground (LU) network. The main aim of this research is to investigate the impact of new tunnel excavations on existing tunnels. This research component is based on field instrumentation and experimental work conducted on half-scale grey cast iron (GCI) tunnel lining segments with chemical composition similar to the Victorian age GCI segments in the LU network. Currently, there is great uncertainty about the behaviour of segmental linings. General belief is that the behaviour of the lining is influenced by the behaviour of the joints, but there has been little experimental work to investigate this relationship. The laboratory experiments aim to find out the deformation behaviour of the bolted segmental lining and the influence of parameters such as overburden pressure, bolt preload and presence of grommets at small distortions. The measured behaviour of the segmental lining is compared against the theoretical behaviour of a continuous lining based on the assumption of linear elasticity. The laboratory results are used to assess the validity of the tunnel assessment methods used by the industry. The results from the parametric tests will form the basis for future experimental investigations taking the half-scale test ring to large deformations and ultimately to failure. The field component involved taking measurements of existing bolted segmental grey cast iron tunnels. Small sections of tunnels constructed at the LU Acton Depot, at Tottenham Court Road Station and in the Central Line running tunnel were monitored to gain an understanding of the deformation of tunnels from construction and self-weight, from ground loading and finally from the influence of adjacent tunnelling works. The thesis proposes recommendations for future in-tunnel monitoring based on the findings obtained in this research.

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Although different parts of the rail industry may have different primary concerns, all are under increasing pressure to minimise their operational energy consumption. Advances in single-train trajectory optimisation have allowed punctuality and traction energy efficiency to be maximised for isolated trains. However, on a railway network safe separation of trains is ensured by signalling and interlocking systems, so the movement of one train will impact the movement of others. This thesis considers methodologies for multi-train trajectory planning. First, a genetic algorithm is implemented and two bespoke genetic operators proposed to improve specific aspects of the optimisation. Compared with published results, the new optimisation is shown to increase the quality of solutions found by an average of 27.6% and increase consistency by a factor of 28. This allows detailed investigation into the effect of the relative priority given to achieving time targets or increasing energy efficiency. Secondly, the performance of optimised control strategies is investigated in a system containing uncertainty. Solutions optimised for a system without uncertainty perform well in those conditions but their performance quickly degrades as the level of uncertainty increases. To address this, a new genetic algorithm-based optimisation procedure is introduced and shown to find robust solutions in a system with multiple different types of uncertainty. Trade-offs are explored between highly optimised trajectories that are unlikely to be achieved, and slightly less optimal trajectories that are robust to real world disturbances. Finally, a massively parallel multi-train simulator is developed to accelerate population-based heuristic optimisations using a graphical processing unit (GPU). Execution time is minimised by implementing all parts of the simulation and optimisation on the GPU, and by designing data structure and algorithms to work efficiently together. This yields a three orders of magnitude increase in rate at which candidate control strategies can be evaluated.

The issue of low adhesion between the wheel and the rail has been a problem for the design and operation of the railway vehicles. The level of adhesion can be influenced by many different factors, such as contamination, climate, and vegetation, and it is extremely difficult to predict with certainty. Changes in the adhesion conditions can be rapid and short-lived, and values can differ from position to position along a route, depending on the type and degree of contamination. All these factors present a significant scientific challenge to effectively design a suitable technique to tackle this problem. This thesis presents the development of a unique, vehicle based technique for the real-time estimation of the contact conditions using multiple models to represent variations in the adhesion level and different contact conditions. The proposed solution exploits the fact that the dynamic behaviour of a railway vehicle is strongly affected by the nonlinearities and the variations in creep characteristics. The purpose of the proposed scheme is to interpret these variations in the dynamic response of the wheelset, developing useful contact condition information. The proposed system involves the use of a number of carefully selected mathematical models (or estimators) of a rail vehicle to mimic train dynamic behaviours in response to different track conditions. Each of the estimators is tuned to match one particular track condition to give the best results at the specific design point. Increased estimation errors are expected if the contact condition is not at or near the chosen operating point. The level of matches/mismatches is reflected in the estimation errors (or residuals) of the models concerned when compared with the real vehicle (through the measurement output of vehicle mounted inertial sensors). The output residuals from all the models are then assessed using an artificial intelligence decision-making approach to determine which of the models provides a best match to the present operating condition and, thus, provide real-time information about track conditions.

The recently discovered squat type defect which is understood as a thermal defect has renewed interest in rolling contact fatigue damage in railway studies. These defects were reported to appear in several locations across the globe where the cost incurred for their removal leads to a major increase of track maintenance cost. While the growth mechanism for classical rolling contact fatigue squat is well understood, limited research has so far been undertaken for squat type defects leaving them poorly understood, especially in their initiation and propagation mechanism. The presence of white etching layer in all locations where these defects have been found strongly suggests that thermal input is responsible for their development rather than fluid assisted growth that is responsible for the development of classical rolling contact fatigue squats. In this thesis, research is reported that combines morphological analysis data with a boundary element model to understand the direct influence of these thermally transformed layers on the initiation and propagation of squat type defects in rail. Furthermore, the work has been extended to explore the possibilities for defect detection in rails reaching a positive proof of concept outcome. It is expected that this approach could serve as a basis for maintenance schedules in order to avoid rail failure due to inadequate understanding of this type of defect.

This thesis presents work undertaken in conjunction with Network Rail in the area of planning and re-planning in railway environments. It aimed to study a real world signalling environment to understand the strategies signallers use when re-planning and how decision tools can be designed and integrated into existing signalling environments to support proactive planning. The main research focused on two case studies: A graphical tool developed by signallers to assist in managing station areas; and the rollout and uptake of a graphical time based planning tool. The first case study consisted of interviews and observations investigating how signallers currently plan (in and around station areas) and what existing tools and artefacts are used, followed by an experiment to compare different tools. It was found that signallers who were using a graphical based tool to assist in managing station areas were able manage disruption more efficiently than signallers using a list based tool. The second case study investigated an existing electronic tool called the Train Graph that had already been implemented. Interviews, observations and questionnaires were used to gather data on the opinions and general uptake of the Train Graph. Trust and prior experience were found to be the significant driver of end user behaviour and uptake of the technology. One key output of this research was a tangible framework that can be used by Network Rail to guide design and implementation of future decision support tools and artefacts. The framework considers the artefact design and various inputs including task characteristics and organisational context as an indicator of performance. If used at an early stage of product development the framework and associated guidelines can be used to influence system design and establish how key implementation considerations impact upon user uptake and trust of the design.

The railway industry is today broadly recognised as a complex sociotechnical system that operates under considerable pressures for increased capacity and reliability. These pressures impact across the industry, in particular on rail engineering because of its responsibility in providing and maintaining the rail infrastructure. Within rail engineering, there is a growing need to address safety and operational risks emerging from high complexity. Planning has been identified as a fundamental organisational function for the safety and efficiency of engineering work. Within this scope, this thesis recognises in the planning of rail engineering work the characteristics of complex sociotechnical systems and investigates planning activities as a part of a wider rail engineering system. Resilience engineering has been recently proposed as a safety management approach that focuses on the development of means for better coping with the variability and uncertainty inherent to large scale complex sociotechnical system. The research documented in this thesis proposes the use of a resilience engineering based approach as a way to improve the ability of the rail engineering planning system to successfully contribute to the safety and efficiency of engineering work. Overall, the purpose of this research was to describe and understand human and organisational factors of rail engineering planning, understand planning performance in view of the support it provides to work delivery, and investigate improvement to the planning system based on resilience engineering concepts. A contribution to the development of resilience engineering as a discipline was also made, mainly through the investigation of possible methods for measuring and monitoring system resilience. The thesis has taken a research approach with emphasis on extensive top-down and cross-organisational exploratory work of the engineering work planning process. This was achieved through the use of quantitative and qualitative methods, namely the analysis of archival data on operational and safety performance, interviews, observations, and a questionnaire. The integration of the researcher within Network Rail’s Ergonomics National Specialist Team (NST) was fundamental for the access to a wide range of data and for the employment of a participant observation approach. The engineering work planning system is described as a complex decision making process, ranging from high level strategic business decisions down to the definition and scheduling of work delivery details. The main human and organisational factors that either hindered or facilitated planning decision making were identified and archival data were used to study planning performance. Results from these research steps were then used to support the understanding and measurement of resilience in planning. Data were interpreted in view of the resilience literature and used as basis for the investigation of potential measurement tools and system interactions with relevance for the understanding of resilience as an emergent system property. The methods used permitted a detailed description of the planning process and the identification of planning performance features within the wider frame of the rail engineering system. Human, organisational and system level factors were identified, which contributed to the understanding of planning and the identification of constraints and facilitating factors on decision making processes. Throughout the duration of this project, contributions to the development of resilience engineering and its methods were made, whilst identifying sources of resilience in the planning system and contributing to the development of measurement tools by means of a questionnaire approach. The understanding of resilience in rail engineering planning was used as a support for recommendations towards the improvement of the planning function’s ability to cope with operational pressures and successfully support work delivery.

Railways are integral to the transportation system of a growing economy. There is a constant demand by numerous stakeholders of the railway industry for greater train operational speeds, tonnage, passenger comfort and safety with minimal service disruptions. This is partly achievable through the improvement of the main components of railway track. A fundamental requirement for any railway track is to be able to maintain its as-built geometry over its service life. Settlement of a ballasted railway track is mainly caused by cyclic loading due to the passage of traffic. To return the rail track to the as-built alignment and level, track maintenance needs to be carried out. Tamping is one of the most common and traditional ways of maintaining the track and is not only costly but causes interruption to the day-to-day operations and damages the long term performance of the ballasted track. It therefore remains important to policy makers, rail practitioners and researchers to identify new techniques, innovations or processes that will prolong intervals between scheduled track maintenance. Track settlement is influenced by several interrelated track variables, not least of which are the railway sleeper, ballast and ballast-sleeper interface that have potential for alteration to be optimised with respect to the track performance. In this research, results are presented from a parametric experimental study using three different apparatus namely box test (confined), Composite Element Test (CET) (semi-confined), and Railway Test Facility (RTF) (full-scale), to investigate performance of different sleeper and ballast configurations. The box test and the CET apparatus were used ahead of the RTF (full-scale) apparatus as preliminary tests to obtain an insight into the performance and potential benefits of different sleeper types with and without the use of Under Sleeper Pads (USPs). The aforementioned apparatus were also used for comparison with the full-scale apparatus to assess the consistency of the sleeper settlement results (phase 1 tests). The purpose of using the box test and CET apparatus was also to allow a relatively large number of simplified tests to be carried out on sleeper and ballast combinations (Phase 2 tests) within a reasonable cost and time frame. Phase 2 tests were designed and conducted with consideration of the phase 1 test results. The test results from phase 1 showed that increasing the number of contact points between ballast particles and sleeper, and increasing the coefficient of friction at ballast-sleeper interface improved the settlement performance of the tarckbed. Therefore, having this in mind, further tests were designed and conducted including: finer ballast grading, two-layered ballast systems, frictional sleepers and USPs, and USP types with various stiffnesses. In addition, further tests on ballast bonding/gluing and ballast reinforcement were conducted with the aim of investigating possible ways of minimising ballast bed deterioration. Application of ballast gluing was proven beneficial (in literature) in improving ballast bed performance, however, the overall cost of super glues used for this method was high. Therefore in this study, a low cost glue was introduced and its performance was tested under conditions similar to real track. With regard to ballast reinforcement, the expanded polystyrene was added to the ballast sample with the aim of decreasing the contact forces between ballast particles and consequently minimising ballast bed deterioration and settlement. The observations in this study sought to establish qualitative and quantitative data on the effects of different parameters on the track performance, which may lead to a longer service life with less maintenance. The results showed that the type of sleeper has an influence on the performance of a railway track. With respect to settlement performance of a railway track, sleepers with higher depth and width, coefficient friction, and bending stiffness performed better. Out of all investigated sleeper types without any additional interventions, concrete mono-block gave the least settlement and the plastic sleeper gave the most. It was also found that inclusion of USPs (regardless of type) can be beneficial compared to the ‘no USP’ scenario in: (1) Increasing trackbed resiliency. (2) Reducing maintenance works related to settlement. (3) Reducing sleeper deflections (hogging) at the middle of sleeper. (4) Reducing the rate of deterioration of sleeper support at the rail seat (6) Reducing differences in the performance of different sleeper types. (7) Reducing tendency towards centre binding. (8) Reducing transmitted pressure on subgrade. (9) Making the trackbed stiffness more uniform. The conclusion of research was that use of concrete mono-block sleeper, USPs, finer ballast grading, a two-layered ballast system with finer ballast grading on top, frictional sleeper, frictional USP, and ballast gluing all have potential to improve the performance of ballasted railway track and reduce the maintenance requirements.