Under the effect of climate change, increasingly intense rainfall has caused frequent failures of UK transport infrastructure slopes/embankments. These failures have severely disrupted the serviceability of the transport network (which are vital in supporting national economic growth) and consequently led to significant socio-economic losses. There have been challenges for the engineers, planners and stakeholders to devise environmentally-friendly stabilisation techniques to withstand the negative impact of irreversible environmental change, while at the same time protecting the natural environment/ecosystems, which underpin the economic prosperity, health and wellbeing of society. Various slope stabilisation methods have been developed, such as sprayed concrete cover and piling. However, these traditional "hard" engineering methods have high embodied CO2, resulting in greenhouse gas emissions that have been linked to further increased climate change. This emphasises the urgency to develop a low-carbon and more sustainable engineering solution that can increase resilience and protect vital transport embankments. The slope bioengineering method (SBM) using stem cuttings (known as live poles) is an aesthetically-pleasing, environmentally- and ecologically-friendly alternative to the traditional "hard" engineering methods, as this technique provides additional environmental and societal benefits of carbon fixation, enhanced biodiversity and ecosystem restoration within the built environment. Plant roots provide direct mechanical stabilisation to embankments and also act as a "bio-pump" during transpiration to remove soil moisture, which in turn increases soil strength and, hence, embankment stability. However, seasonal variation of soil suction due to plant transpiration potentially results in ground surface settlement/heave, which disrupts the serviceability of embankments (e.g. train speed restriction and delay, poor railway track quality and maintenance). Such disruption is more prominent when embankments are made of clay material that is vulnerable to shrinkage/swelling upon soil moisture changes. An interesting question hence arises: Is SBM suitable to be applied to clay fill embankments, and is it capable of maintaining slope stability and preventing from excessive slope deformation simultaneously? The project will evaluate critically the effectiveness of SBM to combat the influence of different climate-change scenarios on the performance of clay fill embankments. The work described in this proposal represents the first systematic physical model tests for small-scale model embankments (made of real soil) supported by novel water-uptake pole models within a geotechnical centrifuge. The pole models will be designed to have similar strength and stiffness to real poles, and will also be capable of simulating the effects of plant root-water uptake in the soil. Highly-instrumented centrifuge tests are designed to investigate holistically whether the change of the soil water regime due to root-water uptake in a bioengineered embankment magnifies the clay shrink-swell response, which in turn leads to seasonally-driven failure and ground surface settlement/heave. Different vegetation management schemes (through selection of plant types and arrangements) will also be examined to optimise the performance of embankments for minimising ground surface settlement, while enhancing embankment stability. The project will provide a unique test database that contains new knowledge for end users to develop increased confidence for wider deploying SBM in practice. The new knowledge and insight derived from this project will not be limited only to transport infrastructure slopes/embankments, but extends also to wider engineering applications. These include enhancing the performance of earthworks for flood defence and landfill covers, which are critical elements of civil infrastructure that are vulnerable to the effects of climate change.

Slope failures (landslides) cause significant disruption to our transport network. In 2015 143 failures like these were recorded on the rail network alone. In addition to causing frustrating delays these failures also cost a significant amount to repair. Failures usually occur during winter months as a result of high rainfall but this is just the end point of a process which may have been occurring for several years. Long exposure to the UK's changing weather causes the compacted clay soil which forms the embankments that our highways and railways are built upon to weaken over time. Very fine cracks develop as the soil is repeatedly dried out and then re-wetted by periods of dry and then wet weather. This effects the way water moves through the soil, the cracks allow water to get deep into the slope very quickly and large pressures can build up, pushing soil particles apart. Ordinarily, during hot dry weather the opposite happens. Water is taken out of the soil by the action of evaporation and transpiration of plants, this induces negative pressures which force soil particles together, strengthening the slope. These negative pressures build up during the summer and help keep the slopes stable during the winter. The capability of soils to generate these negative pressures is reduced by the formation of cracks. A combination of these factors can weaken the soil to such a point where one large rainfall event can cause a slope to de-stabilise. This project will develop a new way of strengthening soil slopes and preventing these types of failure from occurring. Biopolymers, naturally occurring polymers formed by the action of microorganisms, can be added to soil to improve its strength and reduce the potential for cracking. The biopolymers mix with water in the soil to form gels which bind with soil particles giving the soil greater strength and reducing permeability. Biopolymers are already utilised in cosmetics and food as thickening agents so they are relatively cheap. They also do not require significant amounts of energy to produce and therefore they are not associated with high carbon dioxide emissions like other potential soil binders (e.g. cement and lime). Whilst the potential of biopolymers has previously been identified they have not been applied to slope stability problems and the way they form bonds and fill soil pores has not been studied fully. This project will carry out a detailed investigation of how biopolymers interact with compacted soils and use the information gathered to develop a new binder suitable for use in the repair and maintenance of highway and railway embankments.

This partnership started 10 years ago, when Costain started a collaborative research programme with Highways England and the University of Cambridge that sponsored 27 PhD studentships and led to the establishment of three major efforts: (i) the Centre for Smart Infrastructure and Construction, which grew into the National Research Facility for Infrastructure Sensing to develop new methods for infrastructure data collection and analysis using sensors. Our joint work through this activity has collectively shaped national policy; (ii) the EPSRC Materials for Life project that led to a Programme Grant called Resilient Materials for Life, which led to the first UK demonstration of self-healing structures on the A465 road scheme; and (iii) the two EPSRC Centres for Doctoral Training in Future Infrastructure and the Built Environment, which led to Costain acquiring SSL, a data technology company that has accelerated our technology service transformation. All this steered the team to co-create an integrated and focused partnership programme through co-creation workshops, the outcome of which is the proposed Digital Roads partnership. Digital Roads is inherently a concept for how to disrupt the roads infrastructure sector in its entirety. We envision a future where every road is made of smart materials, has its own digital twin, and can measure and monitor its own performance. This will make roads considerably cheaper, more reliable, and safer. Our ambition is therefore to make roads (i) out of smart materials aware of their state and properties, (ii) documented in Digital Twins and monitored automatically, (iii) maintained proactively, and (iv) able to serve additional functionalities, therefore bringing automation efficiency to the road network. The Digital Roads concept rethinks roads as an integrated physical and digital product and associated lifecycle processes that continuously interact with each other to ensure efficiency and strong performance in terms of cost, time, quality, safety, sustainability, and resilience. To support this concept, the grant will therefore investigate how digital twins (for the digital product), smart materials (for the physical product), data science (for the digital lifecycle processes), and robotic monitoring (for the physical lifecycle processes) can work together to create a connected physical and digital product and associated processes with a strong focus on the flow of data between them to leverage their complementarity. For instance, starting from the smart materials: we will use graphene infused concrete coatings to enable self-sensing on both the road surface and the median barrier, that informs the road's digital twin through robotic monitoring, who in turn, along with other pre-existing data, informs the data-science enabled digital processes, and back. This is very timely and necessary, as, after failing to fully leverage technological advances repeatedly over the last 50 years, all the stars are aligned for the road infrastructure industry to leverage advances in information modelling, machine learning, automation and smart materials that now enable the team to have confidence in deliver the Digital Roads vision. Beyond the partnership, the Digital Roads team aims to develop outcomes by 2030 to a commercial stage and to follow the same development journey for other road assets such as bridges and tunnels - and eventually the entire strategic road network by 2040. This will allow Costain to create a leading digital service to deliver for Highways England who will be able to demonstrate greater value roads and enable other industries to do the same. This will ensure that roads become safer, benefiting us all; serviceable at lower cost reducing the burden on the tax payer; and maintained more efficiently and sustainably to benefit the stakeholders, society and the environment making the UK a global leader in Digital Roads technology.

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.

The strength enhancement of structurally deficient concrete infrastructure is an application of considerable economic and strategic importance, particularly in the case of bridges. In the United Kingdom alone, it has been estimated that there are approximately 10,000 bridges on the strategic road network and 150,000 bridges on local roads, of which a considerable number need strengthening or replacement. The estimated cost of assessing and strengthening such structures is in excess of £4 billion. Other countries, e.g. the United States, are faced with the same challenge, so emphasising the global significance of the issue. During the past two decades, fibre reinforced polymer (FRP) reinforcement has gained acceptance as strengthening systems for existing reinforced concrete (RC) structures. The use of FRP strengthening systems is advantageous due to their excellent mechanical and durability properties. Extensive research has resulted in approved FRP flexural strengthening methods for RC structures. In contrast, FRP shear strengthening of RC structures is not yet fully understood. To date, FRP shear strengthening systems for existing RC structures have primarily been applied as externally bonded (EB) or near-surface mounted (NSM) reinforcement. In order to utilise these systems, both sides of individual beam webs must be accessible. However, it is difficult to provide such an access in several practical situations. Moreover, laborious and time-consuming surface or groove preparation is required to ensure adequate bond between the concrete and the EB or NSM systems respectively. Furthermore, unless proper anchorage is provided, both the EB and NSM systems debond from the concrete at a stress level of 20% to 30% of the ultimate strength of the FRP reinforcement. The embedded through-section (ETS) technique is a recently developed shear strengthening method for existing RC structures. In this method, vertical holes are drilled upwards from the soffit in the shear spans of existing RC beams. High viscosity epoxy resin is then injected into the drilled holes and FRP bars are embedded into place. The ETS technique provides higher strengthening effectiveness than that provided by the EB or NSM systems. Other advantages of the ETS technique include higher protection against fire and vandalism, less epoxy consumption, and no need for access to the top slab or time-consuming surface preparation. Research investigating the shear behaviour of RC beams strengthened with ETS FRP bars has been limited. All beams tested to date had effective depths of less than 400 mm. This is unrepresentative of several practical situations where RC bridge beams have significantly higher effective depths. Moreover, the effect of other parameters that influence the structural behaviour of the strengthened beams, such as the shear span to effective depth (a/d) ratio and FRP bar type, has not been sufficiently investigated. A proper understanding of the effect of the above-mentioned parameters on the strengthened behaviour is vital for the best utilisation of the ETS technique. This project will investigate, experimentally and numerically, the effect of a/d and FRP bar type on the behaviour of realistically sized RC beams strengthened in shear with ETS FRP bars. The combination of experiments and numerical techniques will ensure an integrated modelling approach that will inevitably lead to a better understanding of the strengthened behaviour. The experimental results will be used to check the accuracy of current design standards and improve their predictions where needed. The insight gained from this project will enable the utilisation of FRP reinforcement for improving the sustainability and resilience of existing RC infrastructure. The concepts encompassed in this work will underpin our understanding of the behaviour of FRP-strengthened concrete structures and thus have parallel implications in a variety of other areas of concrete construction.