Life Cycle Assessment of Ground Improvement Methods to Enhance the Efficiency of Thermo-Active Geostructures Within Transport Infrastructure

The integration of ground source energy systems with geostructures included in large transport projects–such as tunnels, pavements, retaining walls, and pile foundations–has multiple advantages. Harvesting geothermal energy from geostructures can provide operational energy savings by providing direct geothermal energy for space heating and cooling, deicing of pavements, etc. Incorporating multiple applications into one construction process streamlines construction and reduces cost, and in cases such as road tunnels, where excess heat is generated by traffic, the heat generated from activity and use of the infrastructure can be repurposed rather than wasted. Harnessing the full potential of ground source energy requires collecting and using the energy as efficiently as possible. Tailored ground improvement can assist in increasing the thermal conductivity of the soil surrounding energy geostructures, thereby increasing the efficiency and longevity of each system by allowing for faster heat extraction and dissipation. This article includes the use of life cycle assessment to estimate and assess the environmental impacts of several ground improvement strategies for a thermo-active pile over the full project lifetime, and explores key challenges and technical considerations related to the application of life cycle assessment to ground source energy systems in the context of transport infrastructure. The results of this analysis demonstrate the importance of weighing the environmental impacts of ground improvement additives against their role in improving the efficiency of ground source energy systems. This research is part of a UK government funded project SaFEGround (Sustainable, Flexible and Efficient Ground source heating and cooling systems) which aims to investigate, through multi-scale modelling and assessment, how ground source energy systems can be coupled with geostructures to deliver low-cost, low-carbon heating and cooling.