Numerical Analysis of Ground Surface Settlement Induced by Double-O Tube Shield Tunneling

Abstract

This paper is a case study of the Taoyuan International Airport Access Mass Rapid Transit system, the first project in Taiwan constructed with Double-O-Tube (DOT) shield tunneling. The advancing DOT shield tunneling served to induce ground settlement during construction, which thus impacted the safety of buildings and facilities in neighboring areas. A three-dimensional finite-element program was introduced to simulate the DOT shield tunneling process. Five consecutive rounds were excavated by a tunnel-boring machine from a constructed section; then the longitudinal and transverse ground surface settlements were investigated. Three soil models—a Mohr-Coulomb (MC) model, a Hardening Soil (HS) model, and a Hardening Soil model with small strain (HS-Small)—were used during the numerical analysis. Six monitoring sections along the tunnel alignment and field monitoring data were selected for the investigation. From this study, the ground surface settlements analyzed by the MC model were clearly less than those of the other two models. Because the HS-Small model considered soil stiffness to decay nonlinearly with increasing strain amplitude, it thus showed more-realistic modeling compared to the MC and HS models. This phenomenon was especially evident in the soft-soil stratum. This case study sheds some light on future projects of similar nature.