The research on optimisation problems in network environments has a long history but it generally fails to capture real-world scenarios as it usually assumes that both the network environments (such as network topologies, node processing capabilities, interference, etc) and the optimisation problems (such as the user requirements) are known in advance and remain unchanged in the problem-solving procedure. However, most real-world network optimisation problems (NOPs) are highly dynamic, where the network topologies, availability of resources, interference factors, user requirements, etc., are unpredictable, change with time, and/or are unknown a priori. This poses many difficulties for decision makers, generating significant optimisation challenges. This research aims to investigate Dynamic NOPs (DNOPs) in various network environments. The dynamics in both network environments and problems will be studied in depth. DNOPs occur across a wide range of application areas, such as communication networks, transport network, social networks, and financial networks. Our theoretical study in this project will seek fundamental insight that is applicable to multiple application areas, while our applied research will focus on railway networks and telecommunications networks. Evolutionary Computation (EC) encompasses many research areas, which applies ideas from nature (especially from biology) to solve optimisation and search problems. EC has been successfully applied to many real world scenarios, especially for difficult and challenging problems and those problems that are difficult to define precisely. This project aims to investigate EC methods for solving DNOPs. We aim to gain insight and further our understanding of how different EC methods can be applied to DNOPs via empirical and theoretical studies. It is important to carry out this research at both theoretical and empirical levels, as one can feed into the other. We will work with industrial partners (e.g., Rail Safety and Standards Board, and Network Rail) who will validate our research and participate in our project. We can utilise their skills and expertise in producing the underlying theoretical models, which can then be validated on real-world data supplied by them. This project has great potentials to fundamentally change the way in which DNOPs are treated, both from a real-world point of view and from the point of view of advancing our theoretical understanding. We plan to develop a prototype system, in collaboration with our industrial partners, for our industrial partners. In order to test and evaluate our newly developed algorithms for DNOPs, we will develop a set of common DNOP models that capture the real-world complexities, and develop advanced EC methods to solve these DNOP models. This will benefit wider research communities due to the ubiquity of DNOPs in so many different fields from communication networks to transport networks to social networks to financial networks. The research results of this project will also be of significant benefit to many industries that involve DNOPs and will provide significant savings both from a cost point of view as well as from an environmental perspective.

Railway ballast degrades under traffic loading. The broken fragments fill the pores, making drainage difficult. The ballast then has to be tamped, which involves inserting vibrating tines into the ballast and squeezing it to raise the sleeper back to the appropriate level. However tamping also causes particle breakage. Eventually the ballast is spent and has to be replaced. Five percent of spent ballast ends up in landfill, at a cost of millions of pounds per year. It is therefore desirable to increase ballast life and reduce maintenance costs. In order to do this, it is essential to gain an understanding of the fundamental micro mechanics.The behaviour of ballast can be characterised by triaxial testing; a large cell funded by EPSRC is now being used at the University of Nottingham. Both monotonic tests and cyclic loading tests are used; the cyclic loading tests are used to determine the behaviour of ballast under traffic stresses. In order to understand the particle mechanics, the discrete element method can be used. In the program PFC3D, there are two entities: a ball and a wall. A ballast particle can be modelled as a single uncrushable ball, or more realistically, as an agglomerate of many small balls bonded together. The aim is to model the triaxial testing of crushable ballast to gain insight into its behaviour. Geogrids are used to limit the deformation in ballast by providing interlock. This reduces settlement and therefore maintenance costs and prolongs life of the ballast. However, the ideal geogrid / ballast geometry is not known. The discrete element method will be used here to optimise the system.The outcome will be an improved understanding of ballast behaviour under monotonic and repeated loads, and the effect of geogrids, so that improved trackbeds can be designed such that maintenance costs are significantly reduced and ballast has a prolonged life.

Railways have a vital role in any 21st century transport policy. No other form of transport could cope with the large numbers of people transported into and around major cities every day by commuter railways and metro systems. Trunk lines can shift vast quantities of freight, keeping thousands of lorries off our roads, and intercity routes are increasingly competitive for speed and convenience with domestic air transport. Even in rural areas, railways often offer more reliable and attractive public transport than buses. Environmentally, railways outperform road vehicles and aircraft in terms of energy efficiency, air pollution and noise. However, railways are operating at or beyond capacity. The system can take a long time to recover from a small delay, and disruption on one part of the network can spread rapidly to affect services elsewhere. There is little time for vital maintenance, and last year one train company had to re-write its timetable completely because of unacceptably poor reliability. Travel is becoming increasingly popular, and if the Government's plans to introduce road charging for car journeys cause just 1% of people to switch to rail, the system will be overwhelmed. Rail Research UK is a consortium of twelve university-based groups carrying out research across a range of areas from engineering to human factors and transport economics, that will help to reduce the complexity and need for maintenance of railway systems, reduce their environmental impacts, increase their capacity and improve their reliability, attractiveness and safety.

Performance demands on railway infrastructure in the UK are now greater than ever before and are predicted to increase in the near to medium term. For example, the Pendolino tilting trains recently introduced onto the West Coast Main Line (WCML) operate at higher speeds than ever before when curving and consequently place greater loading on the track than conventional trains. In addition, the line itself was designed to accommodate an increase in the maximum axle load of freight trains from the current 25 tonnes to 30 tonnes. Elsewhere, high speed links from Folkstone to London as part of the Channel Tunnel high speed link will bring TGV speeds to commuter trains into London from the South East. As a result of these increased demands, available maintenance windows progressively become fewer and narrower. This trend will continue, as National Rail moves towards a target of operating a 24-hour rail service. In this context, efficient and cost-effective design of rail infrastructure for maximum performance with a minimum of maintenance is essential.Railway infrastructure predominantly consists of ballasted track, which has many advantages in terms of cost and ease of maintenance. However despite its widespread use the mechanics of railway ballast are still not fully understood. As a result, ballast specification continues to be largely empirical and in some cases driven by the materials to hand. Furthermore, there is lack of scientific understanding of the mechanical behaviour of ballast and how this is affected by traffic and by maintenance operations. An improved knowledge of the mechanics of ballast would enable better design, maintenance and renewal of ballast foundations to carry heavier freight and faster passenger services more intensively. The proposed research will contribute to this by investigating two factors that significantly influence the mechanical behaviour of ballast and its performance as the track foundation: (1) the fabric structure of ballast, and (2) its discrete nature.(1) Fabric structure in granular materials like ballast is the result of particle interlocking, and it is known to have a significant effect on their mechanical behaviour. However, there is currently very little scientific understanding of what the fabric structure of ballast is or how it develops at different stages of the ballast lifecycle, e.g. due to traffic loads or track maintenance. The proposed research will investigate ballast fabric structure by recovering preserved ballast samples from operational railway track and examining in detail how ballast structure develops over time in field conditions. These investigations will be complemented by controlled laboratory experiments, to investigate the development of fabric structure and the resulting mechanical behaviour of ballast under different stress conditions and stress paths, representative of those experienced by ballast on site.(2) The relatively large size of ballast particles in relation to sleeper footprint and ballast depth means that sleepers interact with the ballast through a relatively small number of contact points. Furthermore, in granular media it is known that a small minority of particle contacts exert a disproportionate level of influence over the behaviour of the aggregate, resulting in highly irregular contact pressure distributions at the ballast/sleeper interface which can vary significantly from sleeper to sleeper. The proposed research will use a numerical method allowing simulations of granular aggregates at the particle scale, to investigate this variability in contact pressure and its effect in the overall mechanical behaviour of the ballast below a sleeper.The knowledge and insights gained from this research will contribute to the development of better design criteria and maintenance procedures for ballast foundations, leading to better value and better performing railway track systems for a new generation of trains.

Large engineering structures such as railway and highway earthworks, bridges, pipelines and dams may need to be monitored for a number of reasons. These include general performance monitoring and providing a warning of incipient or actual failure (e.g. a landslip). New infrastructure construction projects, particularly large basements and tunnels in urban areas, may require extensive monitoring systems to enable the resulting ground displacements to be measured and compensated for where necessary. The cost of such monitoring, especially over large geographical areas which may be remote or inaccessible, is significant. More efficient monitoring and early warning systems have the potential to save large sums of money, and even human life. One of the most effective ways of assessing the performance of infrastructure is to measure surface variation (displacement) and relate instability or loss of performance to the rate of change of this variation. A number of technologies are currently used for surface variation measurement; these include extensometers, D-GPS systems, prism monitoring, reflectorless laser systems, photogrammetry, and interferometric linear ground based synthetic aperture radar. All of these systems have advantages and limitations. Many are expensive, some only operate over limited distances, others require installations to monitor particular locations (such as reflectors), and some will not operate in the dark or in poor weather.The use of satellite imagery offers the potential for cost-effective measurement of surface variations. Spaceborne Interferometric Synthetic Aperture Radars (InSAR) make use of orbiting satellites to image a given area. Images from successive passes of the satellite can be used to calculate ground displacements. The primary drawback with spaceborne InSAR surface change detectors is that they were developed for global, rather than local, area monitoring purposes and have a long satellite revisit time. Another potential problem is that using only one or two satellites, an area of interest could be in an electromagnetic shadow (i.e., the satellite cannot illuminate the area due to an obstacle blocking the satellite signal). This can occur especially in urban areas or hilly terrain.Recent advances have enabled the development of a subclass of InSAR using ground surface mounted receivers, the Passive Interferometric Space-Surface Bistatic Synthetic Aperture Radar (PInSS-BSAR). The PInSS-BSAR topology has a stationary receiver fixed on the ground, with the imaging antennae pointed towards the area of interest. A satellite moving relative to the surface generates an electromagnetic ranging signal illuminating the observation area. The signal is reflected by the earth's surface, and received by the radar antennae. By using two antennae, one fixed above the other, it will be possible to calculate the change in displacement in the vertical direction. PInSS-BSAR is best utilised using non-cooperative transmitters, i.e. satellites being used for other purposes. Global Navigation Satellite Systems, such as GPS and Galileo provide large numbers of non-geostationary, simultaneously operating satellites above the horizon, which illuminate a particular region at different angles. At any time, the satellites should cover the entire surface of the planet without any points in electromagnetic shadow. The range of such as system is expected to be kilometres, and its ability to monitor continuously will provide effective early warning of excessive displacements.The proposed research seeks to develop a cost-effective monitoring system using PInSS-BSAR to measure surface variations, with specific application to linear infrastructure such as roads and railways, and their associated embankment and cutting slopes. The prototype device will be verified against existing conventional surface displacement instrumentation already installed to monitor two large failing infrastructure slopes.