Mechanical Mechanism Analysis and Influencing Factors of Subway Cross Passage Construction

Abstract

The construction of the cross passage changes the main tunnels segment from a complete cylindrical structure to a notched unstable stressed structure. Thus, the overall force (bending and shearing) performance of the main tunnels is considerably decreased. The excavation of the cross passage also destroys the stability of the original soil layer and main tunnels and causes difficulty in avoiding the settlement of the surface and main tunnels. Numerical simulation analysis of the mechanical characteristics and influencing factors analysis were carried out using FLAC3D. Results show that (1) the construction of the cross passage largely disturbs the main tunnels. The settlement of the intersection part of the main tunnels and cross passage is mainly concentrated from −7 m to 7 m. (2) During the construction of the cross passage, the original main tunnels are subjected to stress redistribution, which causes stress concentration in the intersecting segments, especially in the opening side segment has an unfavorable force form in which the upper and lower sections are integrally pulled. (3) The construction of the cross passage causes a large tensile stress area in the structure as well. As a result, the overall tension of the upper and lower sections of the structure and the compression of the hance are unfavorable. (4) The influence of the excavation of the cross passage on the surface and main tunnels is related to the buried depth, intersection angle, excavation method, and grouting range. Therefore, the influence of different parameters can be analyzed by changing the model parameters.