Study on Shield-Roof Method using Small Diameter Shield Tunnels based on Numerical Analysis
To connect two existing shield tunnels by non-open cut method, a shield-roof method using several small diameter shield tunnels above and below the existing shield tunnels for earth pressure protection were proposed. But the small diameter tunnels with 3 dimensional sharp curve has never been constructed before, since it is difficult to control the shield following the planed alignment. On the other hand, the operation parameters, such as, copy cutter length, copy cutter range and articulated angle, which give the largest influences to shield behavior, are generally set based on the experience of shield operators. To solve the above mentioned problems, the operation parameters needs to be clarified.
This research aims to confirm the realization of the shield tunnels with small diameter and 3D sharp curve through the following procedures:
1)The operation parameters, such as, copy cutter length, copy cutter range and articulated angle, are calculated by the theoretical control method based on the geometric relation of planed alignment and shield dimension;
2)The operation parameters, which are jack force and jack moment, are computed as an unbalanced acting force on the shield by the kinematic shield model;
3)The simulations of the shield behavior are carried out by the kinematic shield model using the obtained operation parameters; and
4)The possibility of its realization is discussed, comparing the calculated shield behavior with the planed one.
As a result, it was confirmed that the calculated shield behavior has a good agreement with the planed one. Therefore, the conclusion can be made as follows:
1)It is possible to control the shield following 3D sharp curve alignment, if the shieldĦĦis controlled by suitable operation parameters.
2)The operation parameters, calculated by the theoretical control method in terms of copy cutter length, range and articulated angle, are reasonable.
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