Track deterioration has a serious influence on the safety and efficiency (speed restriction) of train operations. Many expensive, disruptive and frequent repair operations are often required to maintain the ballast characteristics due to the problem of settlement. Because of this, a geogrid solution that has proved to be a simple and economical method of reinforcing track ballast is widely used. This project presents an evaluation of the behaviour of geogrid-reinforced railway ballast. Experimental large box pull-out tests were conducted to examine the key parameters influencing the interaction between ballast and the geogrid. The experimental results demonstrated that the triaxial geogrid with triangular apertures outperforms the biaxial geogrid with square apertures and the geogrid aperture size is more influential than rib profile and junction profile. The discrete element method (DEM) has then been used to model the interaction between ballast and geogrid by simulating large box pull-out tests and comparing with experimental results. The DEM simulation results have been shown to provide good predictions of the pull-out resistance and reveal the distribution of contact forces in the geogrid-reinforced ballast system. The discrete element method has also been used to simulate cyclic loading of geogrid-reinforced ballast under confined and unconfined conditions. For the confined condition, box tests have been simulated on unreinforced samples and reinforced samples with different geogrid positions and geogrid apertures. The response of the ballast layer reinforced with geogrid under repeated loading agrees with experimental results. It was found that the optimum location of geogrid is 100 mm depth from base, and the triaxial geogrid outperforms biaxial geogrid. For the unconfined condition, cyclic loading of a trough of ballast has also been simulated, and the sample with the geogrid at 50mm from the sub-ballast layer performs best. It was also found that the used of two geogrids at both 50mm and 150mm from the sub-ballast gave a smaller settlement than using a single layer geogrid, or the unreinforced ballast. The geogrid reinforcement limits the lateral displacement in reinforced zone, which is approximately 50mm above and below the geogrid. Previous investigations have shown that the abrupt stiffness change in track support is often associated with accelerated rates of deterioration of track geometry, high maintenance demand, and poor ride quality. However, at present, there is no detailed understanding of the mechanisms of track geometry deterioration at transition zones. This work provides insight into the factors that can cause or accelerate track degradation at the transition zones, in order to identify and evaluate appropriate mitigation design. A simple track transition model with dimensions 2.1m x 0.3m x 0.45m was simulated by using PFC3D. In order to identify and evaluate appropriate mitigation methods, two kinds of transition patterns, including a single step change and a multi step-by-step change for subgrade stiffness distribution were tested. The influence of the train direction of travel and speed on the transition were also investigated. In addition, geogrid was used in the ballast layer to examine the effects of geogrid reinforcement.

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.

The main work presented within this thesis is a numerical investigation of the effects of crosswind yaw angles upon the aerodynamic characteristics of a high-speed passenger train. The applicability of Computational Fluid Dynamic (CFD) approaches to the simulation of external flow around a passenger train were investigated. Results showed the Delayed DES (DDES) approach produced the highest correlation to experimental results. Ballast heights of 0m, 0.3m and 0.75m were simulated and compared to existing experimental results. Comparisons between cases found that a vortex from the train’s underbody follows the ballast profile. Crosswind simulations were conducted at yaw angles of 0o, 5o, 10o and 15o. The results obtained showed the formation of a large vortex upon the leeward side at yaw angles of 10o and above, this caused a region of low pressure which increased the overturning forces acting upon the train. Generally, crosswinds increased pressures upon the windward side of the train and decreased them upon the leeward side. Slipstream velocities on the windward side were seen to decrease whilst leeward side velocities increased. Results were compared to regulations currently in place for the operation and testing of trains. This enabled comments and suggestions to be made upon existing regulations.

The work presented in this thesis was motivated by the desire of the railway industry to capitalise on new technology developments promising seamless integration of distributed data. This includes systems that generate, consume and transmit data for asset decision support. The primary aim of the research was to investigate the limitations of previous syntactic data integration exercises, creating a foundation for semantic system development. The objective was to create a modelling process enabling domain experts to provide the information concepts and semantic relationships between those concepts. The resulting model caters for the heterogeneity between systems supplying data that previous syntactic approaches failed to achieve and integrate data from multiple systems such that the context of data is not lost when centralised in a repository. The essence of this work is founded on two characteristics of distributed data management; the first is that current Web tools, like XML, are not effective for all aspects of technical interoperability because they do not capture the context of the data; and second, there is little relationship between conventional database management systems and the data structures that are utilised in Web based data exchange which means that a different set of architecture components are required.

Railways worldwide have experienced unprecedented growth over the last decade. The infrastructure of many European railways is becoming increasingly saturated, while the operators face strong demands to increase services and carry more passengers and freight. There has been a high demand for performance improvement, to provide better service to customers. This problem is drawing increasing attention from many parties within and beyond the railway industry. In this research, the author first reviewed and analysed the existing performance measures used in railway transportation. A new generic framework for the measurement and improvement of railway network performance has been proposed, based on the concept of quality of service. The key factors affecting quality of service are identified and analysed. Secondly, the quantification of performance has been identified based on the Quality of Service framework. Multi criteria decision making has been applied to determine the weights of each Key Performance Indicator in the framework. Finally, factors within the railway system have been analysed for their impact on performance with a sensitivity analysis, to support the development of performance improvement plans. A case study has been conveyed to show the influence of the system properties on the performance measured by quality of service.

The technical suitability of hydrogen for railway traction is evaluated in the research. World-wide, diesel fuel is currently the main source of energy for railways but relies on petroleum and emits greenhouse gases. Hydrogen as a secondary energy can be produced from fossil fuels or renewables. Thus, a decrease or elimination of emissions is possible, and reliance on petroleum reduced. A well-to-wheel analysis for diesel, electricity, and hydrogen was conducted to establish overall efficiencies and emissions. The results show that hydrogen fuel cell traction has a similar efficiency to electric traction and reduces carbon emissions compared to diesel and in some case electric railways, if the hydrogen feedstock is natural gas. Renewable hydrogen would reduce emissions further. A prototype hydrogen-powered locomotive, the first in the UK, was constructed and employed for a performance evaluation; both demonstrated that hydrogen is suitable for railway traction. Computer modelling of a diesel-electric regional train, a hydrogen-powered vehicle, and a hydrogen-hybrid version was conducted. The journey time and the range of all three options was the same while energy reductions of 34 % for the hydrogen-only and 55 % for the hydrogen-hybrid, compared to the diesel were achieved.

Point machines are the key actuator used in railways to provide a means of moving a switch blade from one position to the other. Failure in the point actuator has a significant effect on train operations. Condition monitoring systems for point machines have been therefore implemented in some railways, but these condition monitoring systems have limitations for detecting incipient faults. Furthermore, the majority of condition monitoring systems which are currently in use cannot diagnose faults. The ability to diagnose faults is useful to maintenance staff who need to fix problems immediately. This thesis proposes a methodology to detect and diagnose incipient faults using an advanced algorithm. In the main body of this thesis the author considers a new approach using Wavelet Transforms and Support vector machines for fault detection and diagnosis for railway electrical AC point machines operated in Japan. The approach is further enhanced with more data sets collected from railway electrical DC point machines operated in Great Britain. Furthermore, a method to express the qualitative features of healthy and faulty waveforms was proposed to test the transferability of the specific algorithm parameters from one instance of a point machine to another, which is tested on railway electrical DC point machines used in Great Britain. Finally, an approach based on Wavelet Transforms and Neural networks is used to predict the drive force when the point machine is operating. The approach was tested using electrical DC point machines operated in Great Britain. It is shown through the use of laboratory experimentation that the proposed methods have potential to be used in a real railway system.

The optimisation algorithm has been further investigated to understand the influence of the weight coefficients that affect the solution of all the optimisation problems and it is very often overlooked in the traditional approach. In fact, the choice of weight coefficients leading to the optimum among different optimal solutions also presents a challenge and this specific problem does not give any a priori indications. This challenge has been tackled using both genetic algorithms and particle swarm optimisations, which are the best methods when there are multiple local optima and the number of parameters is large. The results show that, when the optimal set of coefficients are used and the optimal positions and capacitances of EDLCs are selected, the energy savings can be up to 42%. The second problem of the control of the storage has been tackled with a linear state of charge control based on a piece-wise linear characteristic between the current and the voltage deviation from the nominal voltage of the supply at the point of connection of the storage. The simulations show that, regardless of the initial state of charge, the control maintain the state of charge of EDLCs within the prescribed range with no need of using the on-board braking resistor and, hence, dissipating braking energy. The robustness of the control algorithm has been verified by changing the characteristics of the train loading and friction force, with an energy saving between 26-27%.

Railway transportation is facing increasing pressure to reduce the energy demand of its vehicles due to increasing concern for environmental issues. This thesis presents studies based on improved power management strategies for railway traction systems and demonstrates that there is potential for improvements in the total system energy efficiency if optimised high-level supervisory power management strategies are applied. Optimised power management strategies utilise existing power systems in a more cooperative and energy-efficient manner in order to reduce the total energy demand. In this thesis, three case studies in different research scenarios have been conducted. Under certain operational, geographic and physical constraints, the energy consumed by the train can be significantly reduced if improved control strategies are implemented. This thesis proposes a distance based model for train speed trajectory optimisation. Three optimisation algorithms, Ant Colony Optimisation (ACO), Genetic Algorithm (GA) and Dynamic Programming (DP), are applied to search for the optimal train speed trajectory, given a journey time constraint. The speed at each preset position along the journey is determined and optimised using these searching algorithms. In a DC railway network, power peaks in a substation are not desirable as they could present safety risks and are not energy efficient. A power peak can be avoided if the control of multiple trains is coordinated. The allocation of inter-station journey time intrinsically affects both service quality and energy efficiency. By identifying an optimal journey time allocation, a multi-objective function targeting both energy efficiency and service quality can be used. In this study, a DC railway is modelled with two parallel railway tracks, five station stops and three DC electric substations. Regenerative braking is studied in this DC electric network using Nodal Analysis (NA) and the Load Flow (LF) method. This study demonstrates that within the neighbourhood of an electric railway network, the journey time allocation for inter-station journeys will affect the total service quality and the energy loss. A GA is applied to find the best inter-station journey time allocation. Finally, this thesis explores the potential of applying advanced power management strategies to a Diesel Multiple Unit (DMU) train. DMU trains have multiple diesel engines which are commonly operated in a homogenous manner. The work presented in this thesis analyses the potential energy savings that may be obtained through the independent operation of the engines. Two widely investigated power management strategies which have been applied to the control of Hybrid Electric Vehicles are studied for a typical DMU railway vehicle. DP is applied to identify the optimal instant power distribution between engines. Based on the optimised results from DP, an adaptive rule-based online strategy is proposed using a non-linear programming optimisation algorithm.

This thesis presents a new experimental technique to determine the structure of train slipstreams. The highly turbulent, non stationary nature of slipstreams make their measurement difficult and time consuming as in order to identify the trends of behaviour several passages of the train have to be made. The new technique has been developed in order to minimise considerably the measuring time. It consists of a rotating rail rig to which a 1/50th scale model of a train is attached. Flow velocities are measured using two multi-hole Cobra probes, positioned close to the sides and top of the model. Tests were carried out at different model speeds. Velocity time histories for each configuration were obtained from ensemble averages of the results of a large number of runs (of the order of 80). From these it was possible to define velocity and turbulence intensity contours along the train as well as the displacement thickness of the boundary layer, allowing a more detailed analysis of the flow. Wavelet analysis was carried out on the experimental data to reveal details of the unsteady flow structure around the vehicle. It is concluded that, although this methodology introduces some problems the results obtained with this technique are in good agreement with previous model and full scale measurements.