Abstract:
The use of thermal integrity testing to verify the quality of deep foundations has increased significantly in the UK and other world markets over the last 5 years. The introduction of distributed fibre optic sensing to this field has broadened the range of applications in which it can be deployed and the types of foundations which can be tested. This paper presents how fibre optic sensing technology can be successfully deployed in the construction environment and, through recent examples, demonstrates the range of foundation techniques to which it can be applied.
Alongside developments in the practical aspects of thermal testing, progress has been made in establishing assessment criteria which can be used to evaluate the results. In addition to a theoretical basis, this paper presents recent examples of comparative studies on foundations which include both thermal integrity testing, cross hole sonic logging and intrusive coring.
The use of distributed strain measurement during pile load testing presents an alternative means to verify the assessment criteria used for integrity testing. By evaluating the localised changes in strain at the position of a detected anomaly, it is possible to determine the effect it has on the structural behaviour of the foundation. This new approach can achieve comparable results to foundation exhumation or intrusive investigation and at a fraction of the cost. This paper presents the findings of several such studies, highlighting the benefits and opportunities for future improvement of the method.