Abstract:
The objective of this study is to examine the mechanism of the long-term settlement induced in shield tunneling. A series of finite element analysis were conducted using PLAXIS 3D on a well document shield tunneling case in Taipei Mass Rapid Transit System. Various simulation were executed assessing the impact of consolidation on long-term settlement using Soft Soil and Hardening Soil with Small-strain models. Simulation to assess the impact of the creep behavior of the soil on the long-term settlement was also executed using the Soft Soil Creep model. The computed surface settlements were compared to the field measurements. It was found from this study that the computed settlement matched the field measurement when creep behavior of the soft soil was considered but if creep was not accounted for, the computed settlement undervalued the field measurements.
Finally, a series of parametric study was executed to examine the influence of various parameters on the longterm settlement. The results obtained from the parametric study of shield tunneling in thick clay clearly distinguished that mechanism of long-term settlement in shield tunneling is predominantly due to creep behavior of the soft soil since consolidation constitutes 5% of the total settlement while creep accounts for 80% of the total settlement.
