Static-Pressure Penetration Field Test of PHC Pipe Pile Based on Fiber Bragg Grating Sensor

Herein, two closed prestressed high-strength concrete (PHC) pipe piles were tested under static pressure at the construction field to explore the applicability of fiber Bragg grating (FBG) sensing technology and elucidate the necessity of temperature compensation. FBG temperature sensor and low-temperature-sensitive FBG strain sensor were symmetrically installed on both sides of the PHC pipe pile using the grooving method. The temperature change and strain state of the pile under static pressure were measured using FBG demodulator. The test result indicates that during the process of pile sinking, the temperature variation of the soil around the pile is 2.62 degrees C. Further, the accuracy of the test results of the low-temperature-sensitive FBG strain sensor will be affected if no temperature compensation measures are undertaken. In this test, all low-temperature-sensitive FBG strain sensors survived, facilitating dynamic and real-time monitoring of the change law of pile-tip resistance, pile-axial force, side-friction resistance, and unit-side friction resistance under static pressure. Moreover, the sensor possessed the function of temperature compensation, which can comply with field test requirements, providing a new method for the application of FBG sensing technology in geotechnical engineering field tests.