Ground surface settlement response to subway station construction activities using pile–beam–arch method

Abstract

A pile–beam–arch method is a shallow tunneling method suitable for constructing urban subway stations with dense surface traffic. The main construction process can be simplified into four stages: excavation of pilot tunnels, installation of piles and beams, installation of arches, and excavation of soil inside the subway station. This study uses numerical calculations to investigate the development law of ground surface settlement during the construction of subway stations. The results indicate that surface settlement gradually increases in the first three stages and rebounds after the fourth stage. Further, pilot tunnel excavation and arch installation are identified as key stages for controlling the surface settlement. Based on these facts, the effects of the sequence of pilot tunnel excavation and the spacing and cross-sectional area of the columns on the surface settlement are studied. The results show that the sequence of pilot tunnel excavation has a significant effect on the development of the surface settlement trough. Further, column spacing and surface settlement exhibit a linear relationship, wherein a shorter spacing leading to low surface settlement. The cross-sectional area of the column exhibits a nonlinear relationship with the surface settlement; the surface settlement is stable when the cross-sectional dimensions are 1.5. × 1.5 m. The Peck formula and stochastic medium theory are used to predict the surface settlement in the pilot tunnel excavation stage. The results are 30%–50% higher than that in the numerical calculation, which indicates their safety and conservatism. The results of this study provide a reference for the selection of construction parameters and the prediction of surface settlement in similar projects.