Measurement analysis on whole excavation of foundation pit and deformation of adjacent metro tunnel

Based on the monitoring data of the foundation pit project in the adjacent metro tunnel in operation, the relationship between the lateral displacement in the deep soil and the deformation of the adjacent metro tunnel during the excavation process of the foundation pit has been studied. The dangerous nodes and key affected areas during the excavation of foundation pit are identified and discussed. It shows that the construction of retaining support structure and the precipitation at the early stage of foundation pit excavation have an initial displacement effect on the stratum and adjacent metro. The long-term unsupported exposure of the retaining structure results in the rapid growth of the lateral deformation of the foundation pit. The excavation of foundation pit has a spatial effect. The lateral deformation is greater at the center than the corner of the foundation pit. The one-way excavation easily causes the superposition of the displacement field and the stress field of the soil in the post-excavation area, causing the maximum deformation of the adjacent tunnel to be moved to the back excavation area; When the excavation depth of the foundation pit is close to that of the adjacent metro, the tunnel structure produces significant horizontal displacement and convergence deformation with "transverse duck egg" type, but the vertical displacement fluctuates little; The lateral displacement curve of the deep soil presents the stepped belly-shape, and the maximum horizontal displacement of the soil is in linear with the tunnel deformation in a small range. However, with the increase in the lateral displacement, the deformation of tunnel deviates from the fitting curve and tends to the superlinear increase, and this should be paid more attention in engineering.