Abstract:Based on the strip deep foundation pit project of overpass under Long-chang road in Shanghai, the key points and difficulties of support design under heavy traffic are summarized from the selection of enclosure, support design, checking calculation and actual measurement. The main conclusions are as follows: considering the safety and economy, it is more reasonable to use section steel cement soil mixing wall for foundation pit within 10m. Tongji FRWS software is used for design checking, and all control indexes meet the specification requirements, but the actual enclosure deformation is obviously too large. Through the sorting and analysis of on-site construction conditions and deformation data, the main reasons for the excessive deformation are untimely support, poor precipitation effect, continuous heavy load of surrounding traffic and weak enclosure stiffness. On the premise of strengthening on-site construction management and other measures, it is still necessary to strengthen the design for the support of this kind of foundation pit. For example, some deep foundation pits consider the close insertion of section steel to improve the retaining stiffness; The spacing of strip drawing for foundation reinforcement is densified, and the reinforcement depth is deepened; It is recommended that the spacing of steel supports be densified to 3 ~ 3.5m.
