A bored pile deficiency detection method based on optical fiber temperature measurement

• The optical fiber temperature measurement is proposed for detecting deficiency of bored piles.
• The method adopts only one optical fiber cable for both measurement and transmission.
• The basic principle of the integrity assessment is described with detection equation derived.
• The temperature rise in the optical fiber is found to be in direct proportion to heating power.

In this paper, a new deficiency detection method for bored piles is proposed based on the optical fiber temperature measurement. In this method, only one optical fiber cable is adopted for both measurement and transmission. By studying the heat transfer process between optical fiber and bored pile, the basic principle of the distributed optical fiber technique for bored pile integrity assessment is described. The detection equation is also derived. In addition, model tests are carried out at different heating powers, and the results show the temperature rise in the optical fiber cable is in direct proportion to the heating power. Deficiencies can be identified from analyzing the coefficients in the temperature rise – heating power expressions. Moreover, different values of temperature rise in air and in concrete are obtained when a same heating power is applied. The results imply that the proposed optical fiber temperature measurement can be considered as a possible way of detecting the bored pile deficiency and its mode by analyzing the values of temperature rise.