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Instrumented pile tests are vital to establish the performance of a pile and validate the assumptions made during initial design. Conventional instrumentation includes vibrating wire strain gauges and extensometers to measure the change in strain or displacements within a pile. While these strain and displacement gauges are very accurate, they only provide strain/displacement readings at discrete locations at which they are installed. It is therefore common to interpolate between two consecutive points to obtain the values corresponding to the data gaps in between; in practice, these discrete instrumented points could be tens of Manuscript Click here to download Manuscript Pelecanos_et_al_Manuscript_7.2.docx 2 meters apart, at depths corresponding to different soil layers, and hence simple interpolation between the measurement points remains questionable. The Brillouin Optical Time Domain Reflectometry fibre optic strain sensing system however is able to provide distributed strain sensing along the entire length of the cable, enabling the full strain profile to be measured during a maintained pile load test. The strain data can also be integrated to obtain the displacement profile. In this paper, three case studies are presented where the performance of three concrete bored piles in London is investigated using both conventional vibrating wire strain gauges and distributed fibre optic strain sensing during maintained pile load tests which enabled comparisons to be made between the two instrumentation systems. In addition, finite element analyses were conducted for the three piles and it was found that the ability to measure the full strain profiles for each pile is highly advantageous in understanding the performance of the pile and in detecting any abnormalities in the pile behaviour.

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