Measurements of Penetration Characteristics of Jacked Piles in Clayey Soil Based on Fiber Bragg Gratings

Abstract

© 2020, Chinese Lasers Press. All right reserved. To extensively study the applicability of Fiber Bragg grating (FBGs) sensing technology in the penetration test of jacked piles, a large-scale model test system is used to conduct the penetration test of jacked piles. This paper uses a fiber grating strain sensor for data testing, while using a spoke type pressure sensor and a fiber grating pressure sensor as control groups. By installing a full-section dynamic spoke pressure sensor and a fiber grating pressure sensor at the end and top of the pile, respectively, the difference between the penetration processes of the jacked piles based on the two sensing technologies is compared and analyzed. Simultaneously, the pile body strain data is collected based on the FBG sensing technology, and the penetration characteristics of the side frictional resistance, the axial force, and the unit side frictional resistance of the pile are studied. Results show that the FBG sensing technology has superior performance in the penetration test of static pressure piles, can accurately reflect the penetration characteristics of jacked piles, and can clearly reflect the pile jacking-in process with the increase of pile driving length. Furthermore, it is found that the driving pressure, the end resistance, the axial force, and the unit side frictional resistance of the pile body have the characteristics of a steady-state penetration. Therefore, this study presents a great reference for the model test and the engineering design of static pressure piles.