Abstract
<title>Abstract</title> <p>Based on a diaphragm wall obstruction-removal project for the undercrossing of an existing metro station in Hangzhou Metro, a diaphragm wall removal method using staged hole-by-hole cutting with a horizontal full-rotation drilling rig is proposed. A three-dimensional finite element model was established using Midas GTS NX to compare the ground settlement and deformation characteristics of the existing station and diaphragm wall under two schemes, namely direct cutting by shield tunnelling and obstruction removal by the horizontal full-rotation drilling rig. The effects of different construction sequences within a single obstruction-removal row and among multiple obstruction-removal rows on the deformation of surrounding structures and soil were further investigated. The results show that the numerical simulation results are generally consistent with the field monitoring data in terms of settlement development trends, and can effectively reflect the ground deformation patterns during steel casing sinking, horizontal obstruction removal, casing extraction, and backfilling. Compared with direct cutting by shield tunnelling, obstruction removal using the horizontal full-rotation drilling rig produces a more concentrated ground deformation zone. The maximum deformation of the existing station is reduced from 3.6 mm to 2.1 mm, and the maximum deformation of the diaphragm wall is reduced from 3.9 mm to 2.7 mm, indicating better structural deformation control. Within a single obstruction-removal row, the settlement and horizontal displacement of the retaining piles under bottom-up construction are 2.4 mm and 0.8 mm, respectively, both of which are smaller than those under top-down construction. Among multiple obstruction-removal rows, the interval group construction scheme results in the smallest retaining pile settlement, retaining pile horizontal displacement, diaphragm wall deformation, and soil settlement among the three schemes. The findings can provide a reference for diaphragm wall obstruction removal beneath existing operating metro stations and for the optimization of construction sequences in similar projects.</p>