Mechanical Behavior Analysis for Parallel Small Spacing Tunnels in a Loess Region

For satisfying the requirements of normal running and enlarged outer section in stabling line, parallel neighborhood metro tunnel with two different inner sections is adopted in Xi’an Urban Rail Transit Line One between North Zaoyuan Road and Hancheng Road. Based on the characteristics of different inner sections and small clear spacing, 2D-FEM was applied to simulate and analyze four construction schemes, of which shield method was adopted in left tunnel with small inner section and double-heading construction method or cross diaphragm method for right tunnel with large inner section. The results show that compared with the construction scheme that the tunnel with small inner section is firstly excavated, the larger tunnel by double-heading constructed is first accomplished can evidently reduce the disturbance effect on surrounding rock, reach better state mechanical of tunnel lining, in order to ensure safety construction.