ChihiroˇˇNAKAJIMA
Control method of articulated shield by geometric conditions
Mitsutaka SUGIMOTO
For excavation of a tunnel with sharp curves, the articulated shield is adopted usually. To ensure reliable construction, the attitude of articulated shield should be controlled precisely. However, many parameters, such as ground conditions, jack forces and moments, articulation angle, and copy cutter length and range, etc. will predominate actual shield attitude. These parameters show co-linearity relation and multiple solutions exist. To weaken co-linearity among those unknown parameters during the control of articulated shield, it is one of solving methods to determine articulation angle and copy cutter length and range from the view of geometrical relations. As for present methods to determine articulation angle and copy cutter length and range, some shield manufacturers developed their own procedures. However, these procedures just can consider the simplest 2-D circular alignment. Furthermore, since different manufacturers have the different considerations about the starting and the end timing of articulation, the analysis results even for the same tunneling project are different. In this thesis, a numerical method to determine articulation angle and copy cutter length on 3-D compound alignments was proposed based on the geometrical relations of tunnel alignment and shield dimension. Furthermore, the validity of the proposed method was discussed, applying the proposed method to some 3-D compound alignments. The conclusions of the entire study can be summarized as follows:
1) Articulation angle ?q depends on the dimension of shield, tunnel alignment, and operation rules of shield rotation.
2) Along major normal direction of tunnel alignment, copy cutter length attains to maximum value. Copy cutter length shows minimum value along opposite direction.
3) The copy cutter length distributes across the major normal direction line about a half of skinplate area.
4) Since the influence of shield shift on articulation angle and copy cutter length is limited, the method to prevent touching between shield skin plate and segment by shifting the shield is considered to be effective.
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