Soki HATASHITA

Analysis of SENS Lining Behavior by Continuous Model

Mitsutaka SUGIMOTO

  In the case of SENS, the primary concrete lining is installed to the space between ground and inner mold continuously. Since the primary lining is a fresh concrete, the inner mold tends to move upward due to buoyancy. After that, the primary lining becomes harden, and the earth pressure begins to act. Through the three-dimensional behavior of the inner mold and installed concrete, it is considered that effective earth pressure will be changed. Therefore, to estimate the earth pressure for the design of inner mold and primary lining, an numerical model, which can simulate the interaction among the ground, inner mold and primary lining, is necessary, taking account of the three-dimensional and sequential construction process.
  The current design method for SENS can not express the stress redistribution in the tunnel axis direction due to the three-dimensional and sequential construction process. In fact, in the load-bearing mechanism model, effective earth pressure is partially reduced to fit the calculated sectional force to the measured one, while this mechanism has not yet been theoretically clarified.
  This research aims to make clear the behavior mechanism of the inner mold and primary lining during the complicated construction process from concrete installation to stripping of inner mold.
  A three-dimensional and sequential analysis model for SENS was used, taking into account the load conditions and the construction process. Appling the developed model to the site data, the validity of this model was confirmed.