Name: Gun KUROHASHI

Study on the Behavior of Primary Lining of SENS

Supervisor: Mitsutaka SUGIMOTO

SENS is a tunnel construction method (System), in which a shield (Shield) excavates ground and stabilizes the face; extruded concrete lining (ECL) is installed as primary lining to support the tunnel; and secondary lining (NATM) is installed after confirming the convergence of the primary lining deformation. SENS comes from the initials of these terms. SENS has been adopted to construct Sanbongihara tunnel on Tohoku Shinkansen firstly. In this project, cracks occurred in the lining in the tunnel axis direction, and ground water leakage through the cracks was observed. This is because the inner-form inside the primary concrete lining is lifted up as the distance from the shield before its hardening. However, the behavior of the lining of SENS has not yet been simulated by numerical models and the cracking mechanism of the lining has not yet been made clear. For the analysis a two-dimensional framework model and a three-dimensional finite element method are used generally, but the former can not take into account the three-dimensional effect of a tunnel, and the latter can not express the lifting behavior of the lining due to buoyancy by concrete pressure and water pressure.
Therefore, in this study, a three-dimensional analysis model for SENS was developed, considering the influence of primary lining behavior, load conditions, and construction process. To validate the proposed model, parameter study on initial displacement, the coefficient of horizontal earth pressure and the coefficient of sub ground reaction, which define the ground reaction curve, was carried out, and the effect of three parameters on the analysis results was examined. As a result, the developed model can simulate the behavior of the primary concrete lining until after demolding the inner-form.


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