Yuki KAKIUCHI

Numerical Analysis of Segment Behavior by Shield Execution Loads

Mitsutaka SUGIMOTO

Recently, shield tunnels have been constructed in deeper underground with sharp curve, as underground space in urban area became congested. Furthermore, segments become thinner and wider for saving its cost. Consequently, the stress in segment during construction tends to increase and then the segment damage during construction has been increased. But these mechanisms have not yet been made clear quantitatively. 
Therefore, the unified FE model, which can consider the influence of the tail force and jack thrust on segments by modeling shield and segment at once, was developed. As a result, the calculated deformation of the segment was smaller than the measured one at the measurement section. This is because the model is a static model. This fact indicates that a phase analysis during excavation is necessary to represent the measured data. 
Therefore, in this study, a phase analysis that is considered harden process of back- filling grout was carried out. To make clear the construction loads acting on segments, the followings were carried out: 
1) The construction loads are estimated through the simulation of the shield behavior using the kinematic shield model; 
2) The 3DFEM analysis on shield tunnel displacement is carried out using the calculated construction loads, and the obtained segment displacements are compared with the field measured data; and 
3) The influence of the construction loads on segment behavior in sharp curve is examined.
As a result, the followings were concluded:
1) The rigid displacement of the segment at second step is increased than that at first step, and the displacement is accumulated by phase analysis.  
2) The proposed model can represent the segment deformation in vertical direction and the rigid displacement of the segment to the convex side of the tunnel.
As a future research, it is recommended to analyze the rigid displacement of the segment with increase of the number of steps in phase analysis.