The lining of a shield tunnel is often constructed using prefabricated concrete ring segments, which are bolted together within the tunnel boring machine to form the tunnel lining. During the erection of the tunnel lining the tunnel boring machine (TBM) remains stationary. Once a tunnel lining ring has been fully erected, excavation is resumed, until enough soil has been excavated to erect the next lining ring. As a result, the constructionprocess can be divided in construction stages with a length of a tunnel ring, often about 1.5 m long. In each of these stages the same steps are repeated over and over again.
In order to model this, a geometry consisting of slices each 1.5 m long can be used. The calculation consists of a number of Plastic phases, each of which models the same parts of the excavation process: the support pressure at the tunnel face needed to prevent active failure at the face, the conical shape of the TBM shield, the excavation of the soil and pore water within the TBM, the installation of the tunnel lining and the grouting of the gap between the soil and the newly installed lining. In each phase the input for the calculation phase is identical, except for its location, which will be shifted by 1.5 m each phase.
This exercise requires the activation of the Geotechnical SELECT entitlements [GSE] in order to be able to use the tunnel designer.
The attached *.p3dlog file contains all the commands to generate the model. With a Bentley Geotechnical SELECT Entitlement [GSE] licence, you can use the commands runner to open the *.p3dlog file and to execute all commands in one go, see also this instruction.
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PLAXIS 3D Tunnel Designer [Videos]