Bearing characteristics of ultra-long piles based on distributed fiber optic sensing technology

Based on a series of pile foundation tests from a project in the Super Headquarters Base in Shenzhen Bay, the load deformation characteristics of super-long piles under different geological conditions and the impact of friction coefficient on pile-soil interaction in numerical simulations are investigated. The FBG (fiber bragg grating) densely distributed fiber optic sensing technology is employed for internal force tests of the piles and the ABAQUS for numerical simulations. The results of the simulated average lateral resistance of the soil layers are compared and analyzed with different friction coefficient values applied to the pile-soil interface. The results indicate that: (1) The load deformation characteristics of bored piles are closely related to the pile length and the properties of the bearing stratum. The axial force of super-long piles decreases linearly with depth, and the end resistance ratio significantly reduces. In cases where the bearing layer consists of moderately weathered granite, the axial force of the test pile decreases in a "bulging" shape along the depth direction, with the end resistance ratio lower than 17.1%. (2) The method for determining the friction coefficient in numerical simulations significantly impacts the simulated lateral resistance of the soil. Multiple friction coefficients at the pile-soil interface can improve the accuracy of the simulated results, depending on the nature of the soil layer.