Experimental study on monitoring model of bearing capacity characteristics of uplift piles based on flexible piezoelectric sensing

As an underground concealed project, pile foundations are often unable to effectively resist groundwater buoyancy, necessitating consideration of anti-floating measures. Given the limitations of current monitoring technologies in achieving real-time, full life-cycle monitoring of uplift piles, the development of distributed, high-precision, and cost-effective monitoring methods remains a key focus in the field. In this study, a sensor-enabled piezoelectric geocable (SPGC) based on flexible piezoelectric sensing is used to monitor the bearing capacity characteristics of uplift piles in a distributed manner. Strain gauges are installed for comparative analysis, and the influences of pile diameter in equal diameter uplift piles and the diameter of the enlarged bottom in enlarged-base uplift piles on their ultimate bearing capacity are investigated. The test results indicate that the variation trend of pile strain obtained from SPGC normalized impedance is generally consistent with that measured by strain gauges, and a linear calculation formula for impedance–strain correlation is established. Significant differences are observed in the axial force and side friction resistance between equal diameter uplift piles and enlarged-base uplift piles. Additionally, the ultimate bearing capacity of uplift piles increases markedly with larger pile diameters and diameter of enlarged bottom. Under the same pile diameter, the ultimate bearing capacity of equal diameter uplift piles is substantially lower than that of enlarged-base uplift piles, with the latter exhibiting a 16.7%-66.7% increase. These findings demonstrate that flexible piezoelectric sensing technology holds promise as a novel solution for the long-term operation and maintenance monitoring of pile foundation anti-floating systems.