Impact Assessment of Common Supported Excavation of Double Foundation Pits on the Adjacent Tunnel

Based on the deep excavation engineering which used the common support design near the range of Suzhou Rail Transit Line 2, a 3-D numerical model was created to make the numerical simulation analysis of the deep foundation pit construction and obtain the comprehensive evaluation of the influence on the nearby subway tunnel stress and deformation when the 3 # and 4 # block foundation pits were excavated. The numerical results show that: when the pits are excavated to the basement, the total displacement value of the tunnel is 1.6mm. Because of the aspect ratio difference between the 3# and 4# block pits, the subway tunnel displacement of every direction trends to the 3# block. And the preserving soil area between the two blocks makes the tunnel stress present a symmetric distribution along the soil area's cross section. The surface settlements of soil behind enclosure structure lead to a great impact on the pipelines, whose maximum reaches 5mm. For comprehensive, the maximum displacement and spring back deformation of the subway tunnel meet the control requirements, with a certain margin of safety.