This paper proposes a special application of Brillouin Optical Time Domain Analysis
(BOTDA) sensors for monitoring the mechanical performance of a steel H-pile during
driving process in a field in Hong Kong. First, basic calibration and the related installation
method of optical fiber sensors (OFS) on pile body were introduced. Second, distributed
strain profiles along the H-pile during driving process were successfully obtained from
optical fiber sensors. Finally, measured strain distributions of the H-pile subjected to two
loading/unloading cycles monitored by OFS were used to interpret field performance of
the driven pile. Monitoring results indicate that the vertical load applied on the pile head
generated significant compressive deformation, which was however mostly released by the
corresponding unloading process. The 1st unloading and 2nd unloading processes released
around 66% and 72% of the total compressive pile deformation, respectively. The shear
stress levels mobilized between H-pile and surrounding soils were limited after each
loading/unloading cycle according to the monitoring results. In addition, loading locations
on the driven pile can be clearly identified from strain/stress distribution profiles. It is
found from the monitoring study that BOTDA based sensors are more useful than some
traditional or other point OFS (such as strain gauges or fiber Bragg grating sensors) to
evaluate the average strain distribution of large scale structures