Investigation of prestressed pipe piles uplift static load test on sandy ground using BOTDA technique

Due to limited research on the mechanical behavior and load transfer mechanism of uplift piles on sandy ground, the Brillouin optical time domain analysis (BOTDA) fiber optic sensing technology is utilized in the field testing of prestressed pipe piles on thick sand ground in the lower region of the Yangtze River. This involves employing specialized techniques such as grooving drilling of the pile body, protective measures for attaching optical fibers, and continuous fiber installation during pile connection. These processes enable distributed measurements and accurate data positioning of stress and deformation in the prestressed pipe pile during the uplift process. The study findings indicate a gradual decrease in axial force along the length of the test pile under the uplift load. The soil resistance on the sides of the pile exhibits effective support in the lower portion, while the upper section experiences less soil resistance. The maximum soil resistance is observed at the bottom of the pile. As the uplift load increases, the axial force gradually transfers downward, predominantly relying on the soil resistance of the prefabricated pipe pile. The use of distributed optical fiber strain sensing technology allows for better monitoring of the impact of construction factors on the uplift bearing characteristics during the penetration of prestressed pipe piles. These research results can be applied to other monitoring projects involving different types of uplift pile bearing characteristics.