Disturbing Effect of Shield Tunnel Down-Traversing Nearby Existing Metro Tunnel

Based on the disturbing effect mechanism of shield construction on surrounding soil and buildings, the construction process of shield tunnel down-crossing nearby existing tunnel is simulated with the FLAC-3D numerical simulation software, taking the engineering situation of a shield section tunnel in Beijing Subway as research objects. The disturbing effect on existing tunnel caused by shield tunnel construction underneath is compared under the different reinforcement scheme and the displacement of existing tunnel structure and ground surface induced by shield tunnel down-crossing is discussed. The comparison between monitoring results and simulation results is presented. The results indicate that shield construction makes the existing tunnel structure have the deformation trend of ovalization. The vertical displacement curve of the existing tunnel structure is wavy, the maximum settlement occurs in the place of about D behind the excavation face, and the uneven settlement mainly occurs in the range between 2 D in front and 3 D behind the excavation face. Besides, the influence range of the vertical displacement of the ground surface caused by construction is within the scope of 20 m from the new metro tunnel axis, and the longitudinal influence range of existing metro tunnel structure is within the scope of 16m before and after the tunnel axis intersection point.