Investigation and numerical simulation study on the vertical bearing mechanism of large-diameter overlength piles in water-enriched soft soil areas

With the development of urbanization, there is an increasing demand for higher land utilization rates, leading to the emergence of high-rise residential and commercial complexes. Additionally, in coastal areas, the presence of soft soil and low bearing capacity of the foundation necessitate higher foundation bearing capacity. Large-diameter, super-long piles have been widely employed in engineering projects to address these challenges effectively. This study analyzes their vertical bearing characteristics through field load tests and determines vertical load distribution and transfer mechanisms by using Brillouin Optical Time Domain Reflectometry. A numerical computation and analysis method based on PLAXIS 3D was established, examining the effects of parameters such as pile diameter, length, and soil modulus on the vertical bearing characteristics. Results indicate that large-diameter, super-long piles mainly bear loads through side friction, with the tip bearing less load. As load levels increase, axial force increases linearly above 40 m depth and becomes nonlinear below. Frictional resistance is significant below 40 m at 3,700 kN load. Parameter analysis shows that increasing pile length and diameter enhances bearing capacity, suggesting this method to improve pile foundation capacity in engineering.