Abstract: This paper presents a case history of estimating the soil improvement zone for the launching end of the Tunnel Boring Machine excavation method in soft soil in Shaoxing Transit Line No. 1. The improvement zone is estimated by three different approaches: namely, elastic plate theory, static approach and sliding instability theory. Numerical analysis of soil deformation and strain at various location of the soil improvement zone was performed by finite element software ABAQUS. The analytical results were compared with the construction monitoring data. The results show that: an improvement zone with a length of 6 meters in the longitudinal direction and a width of 3 meters in transverse direction is appropriate for the launching end of the TBM excavation. The longitudinal length of the improvement zone estimated by elastic plate theory is close to the results of numerical and monitored data. Therefore, the elastic plate theory should be applied in this project.

Key words: TBM launching end, end improvement zone, theoretical analysis, numerical simulation, engineering monitoring