Thermal imaging assessment of drystone retaining walls: some case studies

Drystone retaining walls form an essential part of the infrastructure in hilly and mountainous regions around the world, by providing platforms for roads, buildings and for agricultural terraces. Research carried out in England and in France has led to a good understanding of their behaviour, but it is difficult to determine the details of the construction of individual walls without dismantling them – so it can be hard to tell if apparent defects and deformations are a threat to stability. Replacing every apparently defective or deformed wall would be a waste of resources, yet dismantling a wall would obviously be completely disruptive to its function. Invasive investigation, such as drilling, could easily cause damage to the wall structure and destabilise the wall. There is therefore a pressing need for non-intrusive methods of investigation that can reveal critical aspects of a wall’s construction. Thermal imaging can reveal important information about aspects of a wall’s construction that are critical to its stability. This paper presents case studies and numerical modelling that have contributed to the development of this technique, and demonstrate its potential.