<p>Artificially excavated piles are frequently used in existing embankment slope widening projects because of their superior convenience and economy; however, such piles have many influencing factors and complex mechanical mechanisms and therefore have an impact on the existing railway lines. To characterize the force mechanism of a retaining wall in the process of pile hole excavation and to reveal its influence mechanism on the operating line, monitoring data at various stages of an actual project are analyzed and the change rule of the retaining wall soil pressure and the settlement rule of the existing roadbed are studied. The results show that the value of the retaining wall earth pressure increases and then stabilizes with increasing excavation depth during the pile hole excavation process; this trend is highly fitted by the Platts formula. Different excavation sequences yield consistent earth pressure trends; however, post-excavation pile holes have slightly lower stable pressures than pre-excavation pile holes. Upper pile regions experience decreasing retaining wall pressure with surface distance, differing from the lower pile regions. Existing line subgrade deformation occurs in two stages over time. The existing line is affected by the various excavation orders, with the pouring stage having the most significant impact.</p>