Construction optimization of PBA of Subway station tunnel excavation and its cross section in loess area

Abstract This paper takes the project of Hejiaying Station of Xi’an Subway Line 2 as the background for the study. The dynamic numerical simulation of the construction process of the station by the PBA method is carried out using the 3D finite element method. The changes of surface settlement, vault settlement, headroom convergence and structural stresses are studied up to the intersection of the guide tunnel and large section duct. The research results show that: the construction of the upper guide hole of the station has a small effect on the deformation and internal force of the initial support structure of the duct. The construction of the lower pilot hole will increase the deformation and internal force of the initial support structure of the duct, especially the construction of the lower 2 pilot holes and the lower 3 pilot holes will lead to a significant increase in the deformation and internal force of the initial support structure of the duct. Therefore, it is necessary to make a 10m reservation for the lower guide hole of the main line, and to grout the cross section of the lower guide hole to ensure the safe construction of the cross section.