Abstract: The cast-in-place pile is one of the most common forms of pile foundation. It is very important to conduct the measurement of pile deformation of the cast-in-place pile, which is of great use for understanding the bearing characteristics and quality of the pile. In this paper, optical frequency domain reflectometer (OFDR) is introduced as the most advanced technology in the world to carry out the field test on the high-precision measurement of deformation of the cast-in-place pile. During the test, the pile deformation, pile axial force and pile side friction distribution are obtained in the loading and unloading process. Simultaneously, the pile deformation characteristics and load transfer law are analyzed. The test results show that the strain of pile measured by the optical fiber sensor increases with the loading during the loading phase and decreases during the unloading phase, the pile has a certain residual stress after the unloading, however. Besides, through comparison of the pile force distribution curve in the loading and unloading process, it is found that the pile force has a time lag effect after unloading; the results prove that OFDR technology can achieve the high-precision measurement of pile deformation of the cast-in-place pile, which can be applied to investigate the pile deformation characteristics.

Key words: cast-in-place pile, pile deformation, OFDR distributed optical fiber monitoring, high precision, spatial resolution