CONSIDERATION ON MAIN TUNNEL BEHAVIOR AND DESIGN INDEX OF DRIFT WHEN APPLYING THE CENTER DRIFT ADVANCED METHOD

Abstract

 When the center drift advanced method is applied, ‘dodging effect’, that is, the reduction of the amount of convergence and crown settlement at the time of widening excavation of the main tunnel, and reduction of the sectional force of support members, is often expected. However, the discussion regarding the influence on the mechanical behavior of the main tunnel has been limited.

 In this paper, the mechanical behavior of the Yoshinomoto tunnel with the center drift advanced method was considered with the in-situ measurement data and the result of numerical analysis, and it was found that the dodging effect cannot always be obtained under the extreme fragile ground conditions. Also, the design index of the center drift where the effect was shown was discussed through the analysis considering the size of the drift, the stiffness of the support, and the ground condition.