When tunnels for railways or deep foundations to high rise buildings are built, the first step is to excavate a large hole in the ground. A key challenge is to prevent the excavated hole from collapsing before inserting the final, permenant structure. One way to do this is to pump a special liquid called a support fluid into the open excavated hole. Currently the fluid that is most often used is a suspension of bentonite clay. When this fluid flows into the soil around an excabayion the clay clogs the pore space in the soil at the open face, forming a layer called a filter cake, which prevents fluid and soil movement, and supports the excavation. A newer technology has emerged that uses fluids that are polymer solutions rather than suspensions of small clay particles. These polymer fluids work in a very different way to the bentonite clay suspensions. It is the high viscosity of the fluid that prevents collapse of the hole; these fluids can keep the excavation supported and safe without the need to form a filter cake. Support systems that use polymer fluids are cheaper and have a lower environmental footprint than systems using bentonite suspensions. However the interaction of the polymer fluids and the soil is more complex than the interaction between the soil and the bentonite suspensions. It is therefore more difficult for engineers designing these support systems to predict exactly how they will work and this has slowed their uptake by the construction industry. Our overall aim is to provide the fundamental science needed to reduce any technical uncertainty and therefore enable wider use of these materials. This will have both environmental and economic benefits. In this project engineers with experience of working with polymer-based fluids in the laboratory and on construction sites will team up with engineers who are experts at studying the detail of fluid flow in porous materials to get a much better understanding of how polymer-fluid based support systems work. Members of this newly formed team have backgrounds in civil engineering, mechanical engineering, and petroleum engineering and are based at Imperial College London (ICL), the University of Cambridge (UoC) and the University of Oxford (Oxf). To deliver the research we will link advanced numerical modelling (at ICL) with detailed experimental measurements (at UoC and Oxf ). The planned research will be divided into 4 work packages (WPs). In WP1, researchers at ICL will simulate flow in the pore space using computer models that are created using high resolution 3D X-ray images of the actual pore space. These models will provide a lot of detailed information, but only small volumes can be considered as they use a lot of computer power. Therefore, in WP2 ICL will use a simpler type of model, called a pore network model, to run larger scale simulations to look at the migration of the polymer front in a model of the soil. In WP3, UoC will use a specially developed laboratory apparatus called a permeameter to study the flow of the polymer fluids in real samples of soils; different types of polymer fluids will be considered. In WP4, Oxf will develop and carry out special 2D flow experiments so that we can see the polymer fluid as it flows through the pores in the soil. We will use the experimental data to confirm the computer models work and the computer models will generate data that can't be measured in the laboratory, such as the flow profiles in the 3D voids and the forces on the soil grains. The key questions we will answer for engineers designing excavations will include: (1) How easy it is for the polymer fluid to move through the pores in the soil (we call this the conductivity of the polymer fluid in the soil)? (2) How much stabilizing pressure is exerted on the soil grains as the very viscous polymer fluid flows into the soil? (3) How do the polymer chains suspended in the fluid interact with the soil grains?

CONTEXT In today's rapidly urbanizing world, the need for innovative, sustainable, and efficient infrastructure solutions has never been greater. Underground construction presents a promising avenue to address this challenge, providing the means to expand vital transportation networks, utility systems, and storage facilities while minimizing surface disruption. As urban populations continue to grow, the demand for underground infrastructure will surge, requiring novel approaches that can deliver resilient, cost-effective, and environmentally conscious solutions. This fellowship seeks to harness the power of advanced digital technologies to transform underground construction, aligning with the ongoing global push for smarter, more efficient infrastructure development. CHALLENGE & APPLICATION Underground construction offers immense potential, but it also comes with significant hurdles. The complexity of soil-fluid-structure interactions (SFS) poses challenges that impact construction processes, project timelines, and costs. Traditional methods often struggle to accurately model and simulate these interactions, leading to uncertainties and suboptimal designs. This fellowship addresses this challenge by integrating cutting-edge digital tools, including Building Information Modeling (BIM), digital twins, and advanced data analytics. By doing so, it aims to revolutionize how we approach underground construction, enabling accurate prediction of SFS interactions and optimizing construction methodologies. AIMS & OBJECTIVES The primary aim of this fellowship is to reshape the landscape of underground construction by seamlessly integrating digital technologies. The project's objectives are: 1. Develop advanced digital modeling techniques that accurately predict complex SFS interactions in underground construction scenarios. 2. Create a comprehensive digital twin that integrates real-time data, enabling continuous monitoring and predictive maintenance of underground construction processes. 3. Identify and deploy optimal real-time monitoring technologies to gather data for improving the accuracy of the digital twin. 4. Apply advanced data analytics to optimize construction processes, enabling what-if scenario forecasting and predictive maintenance models. 5. Facilitate knowledge transfer and dissemination of research outcomes to industry professionals, policymakers, and stakeholders, driving the adoption of digital technologies in underground construction.

UK construction is a multi-billion pound industry. While it is the most vital cog in the UK economy for creating physical assets, it is widely regarded as slow to innovate. High risks and the significant cost of mistakes promotes a level of conservatism which is much greater compared to other industries. Change therefore tends to be iterative and cautious. Supported by the UK Government through the implementation of various construction initiatives, such as 'Construction 2025' and 'Transforming Construction', the industry is beginning to embrace technology in a transformative way. The technological revolution is already under way for 'above-ground' construction activities, with modular construction and building information modelling being primary examples. One of the biggest obstacles to underground construction making similar gains is uncertainty surrounding how structures interact with soils during construction operations i.e. 'soil-structure interaction' (SSI). Soil-structure interaction plays a critical role in underground construction operations yet the tools that are used to predict them remain remarkably over-conservative. This is because predictive models for SSI are non-existent, over-simplified or are calibrated against measured data obtained from model-scale replicas of the process in the laboratory, essentially representing an 'ideal' soil-structure interface. The work described in this proposal will develop the underpinning engineering science for SSI design applied to underground construction. Laboratory testing and numerical modelling will be used to elucidate the mechanics of soil-structure interface behaviour such as the role of strain level, stress level and time on the development of soil-structure contact stresses and pore water pressures. Intelligent monitoring systems will be developed to measure and monitor soil-structure contact stresses on live construction projects to provide (i) field data for rigorous validation of developed design methods and (ii) real-time, automated feedback to site engineers to inform construction processes and provide 'early warning' of adverse responses. Recent advances in fibre optic sensing will be exploited to develop novel multi-directional contact stress sensors. The new sensors will alleviate limitations associated with traditional transducers such as excessive sensor flexibility (which actually influences the soil stress field the sensors are intended to measure) and immunity to electromagnetic noise and water damage. A multi-directional interface shear apparatus will be developed to validate the contact stress sensors and provide additional insight into the behaviour of an 'ideal' soil-structure interface in the laboratory. The monitoring system will employ machine learning algorithms in the form of Bayesian non-parametrics such that prior data from previous construction projects may be synthesised with newly-acquired data to provide a robust data-driven decision-making process. The monitoring system will be deployed on live construction projects in the UK alongside industry partners. A suite of new design methods tailored specifically for underground construction operations will be developed, informed by the field monitoring, laboratory testing and numerical modelling. Embracing the innovation and technology developed in this project will allow the construction industry to obtain and utilise intelligent and actionable data that can save time and money, and improve construction safety. This will contribute to the UK becoming a global hub for the rapidly growing market for construction-related services throughout the world.

Civil infrastructure is the key to unlocking net zero. To achieve the ambitious UK targets of net zero by 2050, we require innovative approaches to design, construction, and operation that prioritise energy efficiency, renewable resources, and low-carbon materials. Meeting net zero carbon emissions will require not only significant investment and planning, but also a radical shift in how we approach the design and management of our civil infrastructure. Reliable low carbon infrastructure sector solutions that meet real user needs are essential to ensure a smooth and safe transition to a net zero future. To address these challenges, the UK must develop highly skilled infrastructure professionals who can champion this urgent, complex, interconnected and cross-disciplinary transition to net zero infrastructure. This EPSRC Centre for Doctoral Training in Future Infrastructure and Built Environment: Unlocking Net Zero (FIBE3 CDT) aims to lead this transformation by co-developing and co-delivering an inspirational doctoral training programme with industry partners. FIBE3 will focus on meeting the user needs of the construction and infrastructure sector in its pursuit of net zero. Our goal is to equip emerging talents from diverse academic and social backgrounds with the skills, knowledge and qualities to engineer the infrastructure needed to unlock net zero, including technological, environmental, economic, social and demographic challenges. Achievable outcomes will include a dynamic roadmap for the infrastructure that unlocks net zero, cohort-based doctoral student training with immersive industry experience, a CDT which is firmly embedded within existing net zero research initiatives, and expanded networks and outward-facing education. These outcomes will be centred around four thematic enablers: (1) existing and disruptive/new technologies, (2) radical circularity and whole life approach, (3) AI-driven digitalisation and data, and (4) risk-based systems thinking and connectivity. FIBE3 doctoral students will be trained to unlock net zero by evolving the MRes year to include intimate industry engagement through the novel introduction of a fourth dimension to our successful 'T-shaped' training model and designing the PhD with regular outward-facing deliverables. We have leveraged industry-borne ideas to align theory and practice, streamline business and research needs, and provide both academic-led and industry-led training activities. Cohort-based training in technical, commercial, transferable and personal skills will be provided for our graduates to become skilled professionals and leaders in delivering net zero infrastructure. FIBE3's alignment with real industry needs is backed by a 31 strong consortium, including owners, consultants, contractors, technology providers and knowledge transfer partners, who actively seek engagement for solutions and will support the CDT with substantial cash (£2.56M) and in-kind (£8.88M) contributions. At Cambridge, the FIBE3 CDT will be embedded within an inspirational research and training environment, a culture of academic excellence and within a department with strategic cross-cutting research themes that have net zero ambitions at their core. This is exemplified by Cambridge's portfolio of over £60M current aligned research grant funding and our internationally renowned centres and initiatives including the Digital Roads of the Future Initiative, the Centre for Smart Infrastructure and Construction, Cambridge Zero and Cambridge Centres for Climate Repair and Carbon Credits, as well as our strong partnerships with UK universities and leading academic centres across the globe. Our proposed vision, training structure and deliverables are exciting and challenging; we are confident that we have the right team to deliver a highly successful FIBE3 CDT and to continue to develop outstanding PhD graduates who will be net zero infrastructure champions of the future.