Abstract: Based on the hydrogeological conditions of Changzhou, this paper analyzes the sensitivity of subway tunnel to the geological condition of groundwater bearing sand layer. A case history of Xinqiaozhongqiao highway over existing Metro Line No.1 is presented. This paper also analyzes a series of protective measures for the subway construction near the bored pile and monitors the subway tunnel structure during the construction period. The monitoring results show that, in the project, the protection measures for the construction risk of cast-in-place bored pile are effective. During the whole pile foundation construction process, the changes of the subway tunnel are within the control range, and the tunnel structure is safe. The monitoring data also reflect that the pile foundation construction with a distance of more than 5m from the tunnel has a small impact on the tunnel. The deformation mainly occurs during the construction of the pile foundation in the middle of the two tunnels. The structure of the subway tunnel has a significant impact on the construction of the tunnel The external vibration load is relatively sensitive, so it is necessary to carefully consider the impact of vibration load on the deformation of track segment during construction; due to the impact of pile foundation density, the tunnel deformation in the forward projection area of the bridge is relatively large, gradually reducing to both sides, and the overall distribution is in the groove shape. The tunnel is basically unchanged about 10 m outside the projection.

Key words: Adjacent pile foundation, subway protection, tunnel, monitoring, deformation