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?

The latest report of Intergovernmental Panel on Climate Change (IPCC) 'Global warming of 1.5C' emphasises the need for 'rapid and far-reaching' actions now to curb carbon emission to limit global warming and climate change impact. Decarbonising heating is one of the actions which is going to play a key role in reducing carbon emission. The Committee on Climate Change states that insufficient progress has been made towards the low carbon heating homes target that requires immediate attention to meet our carbon budget. It is well known fact that the ground is warmer compared to air in winter and cooler in summer. Therefore our ancestors build caves and homes underground to protect them against extreme cold/hot weather. Geothermal energy pile (GEEP) basically consists of a pile foundation, heat exchanging loops and a heat pump. Heat exchanging loops are usually made of high density polyethylene pipes and carry heat exchanging fluid (water and/or ethylene glycol). Loops are attached to a reinforcement cage and installed into the concrete pile foundations of a building to extract the shallow ground energy via a heat pump to heat the building during winter. The cycle is reversed during summer when heat is collected from the building and stored in the ground. GEEP can play an important role in decarbonising heating as it utilises the sustainable ground energy available under our feet. High initial cost remains the main challenge in deploying heat pump technology. In the case of GEEP, the initial cost can be reduced, if the heat capacity of the concrete is improved and loop length can thus be decreased. This can be achieved by incorporating phase change material (PCM) in the concrete. PCM has a peculiar characteristic that it absorbs or releases large amount of energy during phase change (solid to liquid or liquid to solid). This project aims to develop an innovative solution by combining two technologies GEEP and PCM to obtain more heat energy per unit loop length which would reduce the cost of GEEP significantly. PCM has never been used with GEEP in the past, therefore obvious research questions that come to the mind are (1) how to inject PCM in concrete (2) what would be the effect of PCM on concrete strength and workability (3) how PCM would affect load capacity of GEEP as primary objective of the GEEP is to support structure (4) how much heat energy would be available (5) what would happen to the ground temperature surrounding GEEP (6) how much it would cost (7) whether it would reduce carbon footprint of concrete. We aim to answer all the above research questions by employing sustainable and environmental friendly PCM and impregnate it in light weight aggregates (LWAs) made with waste material (e.g. fly ash, slag, glass). There are three advantages of using LWAs made from waste: first LWAs will replace natural aggregate in concrete as natural aggregates are carbon intense, second LWAs are porous and light so they can absorb large amount of PCM and reduce the weight of concrete, third reuse the waste. Laboratory scale concrete GEEP will be made with PCM impregnated LWAs and tested under heating and cooling load to investigate thermal (heat transfer) and mechanical (load capacity) performance. Extensive experimental and numerical study will be carried out to design and develop novel PCM incorporated GEEP which can provide renewable ground energy for heating and cooling.

The surface urban transport infrastructures - our roads, cycle ways, pedestrian areas, tramways and railways - are supported by the ground, and hence the properties of the ground must control to a significant degree their structural performance. The utility services infrastructure - the pipes and cables that deliver utility services to our homes and which supports urban living - is usually buried beneath our urban streets, that is it lies below the surface transport infrastructure (usually roads and paved pedestrian areas). It follows that streetworks to install, replace, repair or maintain these utility service pipes or cables using traditional trench excavations will disrupt traffic and people movement, and will often significantly damage the surface transport infrastructure and the ground on which it bears. It is clear, therefore, that the ground and physical (i.e. utility service and surface transport) infrastructures exist according to a symbiotic relationship: intervene physically in one, and the others are almost inevitably affected in some way, either immediately or in the future. Moreover the physical condition of the pipes and cables, of the ground and of the overlying road structure, is consequently of crucial importance in determining the nature and severity of the impacts that streetworks cause. Assessing the Underworld (ATU) aims to use geophysical sensors deployed both on the surface and inside water pipes to determine remotely (that is, without excavation) the condition of these urban assets. ATU builds on the highly successful Mapping the Underworld (MTU) project funded by EPSRC's first IDEAS Factory (or sandpit) and supported by many industry partners. The MTU sandpit brought together a team that has grown to be acknowledged as international leaders in this field. ATU introduces leaders in climate change, infrastructure policy, engineering sustainability and pipeline systems to the MTU team to take the research into a new sphere of influence as part of a 25-year vision to make streetworks more sustainable. ATU proposes to develop the geophysical sensors created in MTU to look for different targets: indications that the buried pipes and cables are showing signs of degradation or failure, indications that the road structure is showing signs of degradation (e.g. cracking, delamination or wetting) and indications that the ground has properties different to unaltered ground (e.g. wetted or eroded by leaking pipes, loosened by local trench excavations, wetted by water ingress through cracked road structures). For example, a deteriorated (fractured, laterally displaced, corroded or holed) pipe will give a different response to the geophysical sensors than a pristine pipe, while wetting of the adjacent soil or voids created by local erosion due to leakage from a water-bearing pipe will result in a different ground response to unaltered natural soil or fill. Similarly a deteriorated road (with vertical cracks, or with a wetted foundation) will give a different response to intact, coherent bound layers sitting on a properly drained foundation. Taking the information provided by the geophysical sensors and combining it with records for the pipes, cables and roads, and introducing deterioration models for these physical infrastructures knowing their age and recorded condition (where this information is available), will allow a means of predicting how they will react if a trench is dug in a particular road. In some cases alternative construction techniques could avert serious damage (e.g. water pipe bursts, road structural failure requiring complete reconstruction) or injury (gas pipe busts). Making this information available will be achieved by creating a Decision Support System for streetworks engineers. Finally, the full impacts to the economy, society and environment of streetworks will be modelled in a sustainability assessment framework so that the wider impacts of the works are made clear.