Research on the mechanics differences between single-row and double-row side piles of station using the PBA method

The side pile is a crucial mechanical component in station construction using the PBA (pile-beam-arch) method, and its stability during the construction process cannot be overstated. The mechanical differences between single-row and double-row side piles in this construction method have garnered significant attention, yet few studies have been conducted on this matter. Therefore, this paper employs numerical simulation to compare the deformation and mechanical properties of single-row and double-row side piles (the adopted pile type is micro steel pipe pile, abbreviated as MSPP) in a metro station using the PBA method. The findings are validated through the model experiment. It is found that the soil arch effect created by the front-row pile of the double-row piles serves as the primary lining, offering a certain shielding effect to the soil stress behind the back-row pile. Notably, the soil stress values in double-row pile conditions are slightly higher compared to single-row pile condition, leading to a noticeably smaller final deformation of the pile top. The combined bending moments and axial forces of the front-row and back-row piles in double-row piles exceed those of a single-row pile. Specifically, bending moments are highest in single-row piles, followed by front-row piles and then back-row piles, while axial forces are highest in single-row piles, followed by back-row piles and then front-row piles. This suggests that the bending moments and axial forces of double-row piles are smaller than those of a single-row pile. The internal force distribution within the double-row pile is more balanced, thereby enhancing the lining strength and improving the station’s safety through the PBA method. The findings in this paper can serve as valuable references for the design and construction of similar projects.