Abstract:

A portion of the running tunnel from Zaoyuan North Road Station to Hancheng Road Station on No. 1 line of Xi’an Metro is designed as a closelyspaced Metro tunnel with different crosssection dimensions. The parallel tunnel tubes have such features as different crosssection dimensions, dual construction methods (shield tunneling method and NATM) and small spacing. Numerical simulation is made on the construction of the left small crosssection tunnel tube by shield tunneling method and the right large crosssection tunnel tube by double side drift method and CRD method. The calculation results show that: 1) Compared to the scheme that the left small crosssection tunnel tube is broken through before the right large crosssection tunnel tube is excavated, the scheme that the right large crosssection tunnel tube is broken through by NATM before the left small crosssection tunnel tube is bored by shield has smaller disturbance on the surrounding rock mass and is more helpful for ground deformation control; 2) Compared to CRD method, double side drift method is more helpful to making full use of the selfsupport capacity of the surrounding rock mass, is more helpful to making full use of the loadbearing capacity of the primary support, and is more helpful to improving the safety reserve of the secondary lining; however, if CRD method is adopted for the right large crosssection tunnel tube, which is broken through before the left small crosssection tunnel tube, the construction cost can be reduced, the construction progress can be improved and the tunnel can be constructed successfully under safe conditions.

Key words: parallel tunnel tubes with different crosssection dimensions, small spacing, shield tunnelling method, New Austrian Tunnelling Method(NATM), construction scheme selection, monitoring