Integrity Testing of Pile Cover Using Distributed Fibre Optic Sensing

Yi Rui, Cedric Kechavarzi, Frank O’Leary, Chris Barker, Duncan Nicholson, Kenichi Soga*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

35 Citations (Scopus)
4 Downloads (Pure)


The integrity of cast-in-place foundation piles is a major concern in geotechnical engineering. In this study, distributed fibre optic sensing (DFOS) cables, embedded in a pile during concreting, are used to measure the changes in concrete curing temperature profile to infer concrete cover thickness
through modelling of heat transfer processes within the concrete and adjacent ground. A field trial was conducted at a high-rise building construction site in London during the construction of a 51 m long test pile. DFOS cables were attached to the reinforcement cage of the pile at four different axial directions to obtain distributed temperature change data along the pile. The monitoring data shows a clear development of concrete hydration temperature with time and the pattern of the change varies due to small changes in concrete cover. A one-dimensional axisymmetric heat transfer finite element (FE) model is used to estimate the pile geometry with depth by back analysing the DFOS data.
The results show that the estimated pile diameter varies with depth in the range between 1.40 and 1.56 m for this instrumented pile. This average pile diameter profile compares well to that obtained with the standard Thermal Integrity Profiling (TIP) method. A parametric study is conducted to examine the sensitivity of concrete and soil thermal properties on estimating the pile geometry
Original languageEnglish
Article number2949
Number of pages21
Issue number12
Early online date19 Dec 2017
Publication statusPublished - 19 Dec 2017

Bibliographical note

Acknowledgments: The authors thank the EPSRC and Innovate UK for funding this research through the Cambridge Centre for Smart Infrastructure and Construction (CSIC) Innovation and Knowledge Centre (EPSRC grand reference number EP/L010917/1). The authors also acknowledge the assistance of Vivien Kwan,
Purnawarman Musa, Yue Ouyang and Peter Knott. The data presented in this paper are available at the University of Cambridge data repository. (


  • distributed fibre optic sensing
  • pile
  • heat transfer
  • integrity testing
  • finite element


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