Name:Hiroaki ABE
Numerical Analysis on the Lining Behavior of SENS
Supervisor: Mitsutaka SUGIMOTO
SENS has been adopted for the first time in the world during the construction of Sanbongihara tunnel on the Tohoku Shinkasen. In the above project, cracking occurred in the longitudinal lining of the tunnel, and underground water furthermore observed to leak through the cracks. It is considered that the cracking is due to the floating of the inner mold in the unconsolidated concrete of the primary lining as it separates from the shield machine.
However, Behavior of the lining of SENS is not be represented by the analysis, crack generation mechanism is not clear. As the analysis technique, in general, there is a three-dimensional finite element analysis and two-dimensional framed structure analysis. The former can not consider a three-dimensional effect of the tunnel, and the latter can not represent the behavior of lining that is lifted by buoyancy due to water pressure and concrete pressure.
Therefore in this study, we have developed a three-dimensional analysis model that takes into account the loading conditions and construction process, factors understood to affect behavior of the inner mold and lining in SENS.
In this study, we implemented parametric analysis about some values that define the ground reaction curve. Those values are initial displacement, horizontal earth pressure coefficient and the coefficient of ground reaction. In order to verify the validity of the analytical model, we understood the effect of the three parameters has on the analysis result. By comparing the measured value with the analysis values of bending moment and axial force, and we estimate parameters. As a result, we found the following.
(1) When effective concrete casting rate becomes 97% (initial displacement=10mm), ground stress and concrete pressure is roughly balanced.
(2) By the concrete pressure, excavation surface deformed Horizontal, effective earth pressure acting on the inner mold frame and the primary lining is close to equal pressure distribution.
(3) Estimate of the coefficient of ground reaction is substantially coincides with the value calculated from the modulus of elasticity by field survey.
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