Study on Deformation Control Value for Urban Rail Transit Foundation Pit Project

Objective Setting deformation control values for the monitored project and controlling the construction safety is a very important task in the construction of urban rail transit engineering, aiming to ensure the stability of the structure itself and the surrounding environment during construction. When the open-cut method is adopted, the deformation control values vary significantly with different geological conditions, and further clarification is needed on the mentioned values for foundation pits under different geological conditions. Method In the case study of a Beijing metro foundation pit project, the monitored data of the project are collected respectively from two areas (west, middle east) and then processed. The selected monitoring items include the ground settlement of foundation pit, the settlement and the horizontal displacement of the retaining pile top and wall top, the horizontal displacement of the retaining pile body and wall. Statistical analysis method is used to conduct in-depth study on the control values of the above four types of monitoring items, and on the relationship between the deformation value and the design depth H of foundation pit. Recommended control values of the four types of monitoring items are put forward for the foundation pits in two areas respectively. Result & Conclusion The recommended control values of the four types of monitoring items are as follows: 25~40 mm and 0.10%H~0.20%H， 15 mm, 25 mm， 25~40 mm and 0.10%H~0.20%H for foundation pits in the western area, and 30~50 mm and 0.15%H~0.30%H, 20 mm, 20 mm， 30~50 mm and 0.15%H~0.30%H for foundation pits in the middle east area.