On numerical simulation of tunnel installation

The design of tunnels requires a proper estimate of surface settlements and lining forces. In engineering practice different design methods tend to be used, varying from simple empirical and analytical formulations to advanced finite element analyses. This paper begins with a review of empirical and analytical analyses for settlements and lining forces placing emphasis on the sequences of excavation and installation of support. Such installation procedures range from open face to closed face tunnelling and they tend to have a significant effect on deformations and lining forces. Hereafter the focus is on two-dimensional FE-analyses; again both for open face and for closed face tunnelling. Results for different installation procedures will be presented on the basis of two case studies. It is shown that installation procedures are most important to be considered in order to arrive at proper predictions for tunnelling settlements, horizontal deformations and lining forces. For the installation of closed face shield tunnelling a novel simulation method is presented, named the grout pressure method. It is shown that the grout pressure method yields the best predictions for both ground movements and structural forces.