Ryohei NAKAMURA

Numerical Analysis on Articulation Angle and Copy Cutter Length Along 3-D Tunnel Alignment

Mitsutaka SUGIMOTO

Due to the congestion of underground structures and the limitation of underground space for construction in urban area, in recent years deep underground space has been used and the tunnels with sharp curves has been constructed. Articulated shield is usually adopted for excavation tunnel with large radius. Articulated shield can be divided into front body and rear body. To construct tunnels along planned alignment during excavation at curved area, front body is bended against rear body to excavate the ground smoothly at a curved alignment. Shield is advanced by jack forces and copy cutter excavates the ground at the concave side of a curved alignment. Then so far, these operations used to be conducted using expert system based the engineers or automatic excavation system. However, there is no theoretical background to control shield since these systems are based on empirical way. Therefore, it is difficult to control shield behavior under complex conditions. Furthermore, it is considered the demands for construction under deep underground space and adjacent construction near existing structures will be increased. Conventional control method of shield needs to be changed over to theoretical control method, which takes force equilibrium conditions into consideration.
In this study, a numerical method to calculate articulation angle and copy cutter length and range, which gives the largest influences to shield behavior, was proposed, based on geometrical relation of tunnel alignment and shield dimension. To verify the proposed method, the numerical method was applied to three types of shield dimension and alignments. Furthermore, articulation angle and copy cutter length and range were calculated using planed alignment and shield dimension at an actual construction site, and the calculated results were compared with measured data. 
As a result, the followings were obtained: 
1) The articulation angle depends on an operation rules of shield rotation in curved area, the dimension of shield and tunnel alignment.
2) The copy cutter length and range distribute across the major normal direction of the tunnel alignment about a half of skinplate area.
3) The maximum value of copy cutter length exists along major normal direction of the tunnel alignment.
4) The numerical method developed in this study is applicable to actual construction site.