Dynamic Monitoring of the Standard Penetration of PHC Tubular Piles and Analysis of the Construction Effect Based on Monocular Visual Digital Photography

The penetration of large-diameter tubular piles and their relevant construction effect have significant influences on the bearing capacity of piles and nearby buildings (structures). This study focuses on developing an indoor test model device for the dynamic field monitoring of the construction effect of penetrated large-diameter tubular piles based on monocular visual digital photography. The results show that the relationship between the penetration of the tubular piles and time function (blow counts) changes from a logarithmic function to a linear function when piles penetrate from the loose layer to the sandy layer, and then to the silty soil layer. The penetration rates differ significantly under different formation conditions. There are obvious plugging and squeezing effects as tubular piles penetrate different strata. The plugging effect radiates outward in a rectangular shape. The influence sphere of the squeezing effect is divided into the shear failure zone, radial squeezing zone, and hemispherical expansion zone. According to the measurement data, the squeezing effect increases first and then weakens during the construction of tubular piles. This makes the adjacent pile deviate from the initial position by 17.4 mm, making the next pile deviate from the initial position by 6.4 mm, to the maximum extent. This further verifies the superiority of pile-jumping construction. The research conclusions can provide reasonable suggestions and a reference basis to improve the penetration parameters of tubular piles and optimise their construction techniques.