Abstract
The support used when a tunnel is excavated by a shielded TBM is complex because it consists of two different materials: A concrete segmental lining and a filler annulus between the lining and the tunnel wall. A detailed analysis of the behavior of such a support system requires a three-dimensional numerical modeling and should also consider the presence of the TBM machine. This article presents an analytical calculation procedure that allows to assess the interaction between the support system and the tunnel using the convergence-confinement method and Vlachopoulos-Diederichs method. Furthermore, it is defined the overall stiffness of the support system starting from the detailed analysis of the stresses and strains developed in the two constituent materials. From the analysis of the evolution of the radial displacements in the longitudinal section, it was then possible to evaluate another fundamental parameter: The radial displacement of the tunnel wall at the point of installation of the support system. The computational procedure was then applied to a specific case, showing the influence of the stiffness of the filling material on the final loads acting on the segmental lining.
Highlights
Often nowadays tunnels are excavated through the use of machines TBMs (Benato and Oreste, 2015)
The mechanical characteristics of the used concrete are the following: E = 28000 MPa, ν = 0.15. It is assumed the use of natural or injected gravel as a fill of the outer ring of the support system, with an elastic modulus ranging from 100 MPa to 4000 MPa (Poisson's ratio of the filling material was assumed equal to 0.3)
The support of a tunnel excavated using a shielded TBM machine requires the presence of two different materials: The concrete segmental lining mounted in the tail of the TBM shield and a filling material inserted in the inter space between the segmental lining and the tunnel wall
Summary
Often nowadays tunnels are excavated through the use of machines TBMs (Benato and Oreste, 2015). The construction of a tunnel with shielded TBM machines requires the realization of a concrete lining (segmental lining) in the tail of the machine, at a certain distance from the excavation face (10-12 m). A thorough analysis of the interaction between a tunnel excavated by shielded TBM and segmental lining can be developed with the numerical modeling, preferably of three-dimensional type (Do et al, 2014a; 2014b). This modeling turns out to be quite complex and computation times are typically high
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