Monitoring scheme for deep foundation pit of underground parking lot
The plot of China (Shanghai) XX Audiovisual Base (XXX Project) is located at XX Road, the east of XX Exit of XX Road, and the west of XX East Road, XXX District, XX District, Shanghai. In terms of location, the base is located in the east of XX Science Park. The overall planning covers an area of about 220 mu, with a total planning area of about 450000 square meters and a total land area of about 145528 square meters. The project is divided into two areas, A and B, of which A is divided into two areas, south and north (referred to as A South Area and A North Area for short). There are three 7-floor R&D buildings, one 8-floor R&D building in South Area A, and one 7-floor R&D building and one 8-floor R&D building in North Area A; Zone B has two 15F commercial office buildings, one 9F three-dimensional garage, one 9F training center, and a 3F podium. There are two underground garages in the west of Area A and Area B, and three underground garages in the east of Area B (including one underground mezzanine). The construction object of the foundation pit enclosure is the two or three story underground parking garage. ± 0.00 in this project is equivalent to the absolute elevation of+6.00m. According to the geotechnical engineering survey report and design scheme, the absolute elevation of the natural ground after site leveling is considered as 4.40 m, that is, the relative elevation is -1.60 m. The excavation depth of the foundation pit in Area A is 8.8~9.4 m, the excavation depth of the foundation pit in the west of Area B is 10.05~10.35 m, the excavation depth of the foundation pit in the east of Area B is 11.05~12.25 m, the depth of the deep pits such as the water collecting well and elevator well is 1.0~1.5 m, and the depth of the fire water collecting well is 2.9 m. The foundation pit of this project is approximately fan-shaped, with an area of about 82743m2 and a perimeter of 1354m. Foundation pit retaining structure and reinforcement method: the excavation depth of the foundation pit of this project is relatively deep, up to 12.25m locally. The excavation area of the foundation pit is large, and the surrounding environment is general. According to the Shanghai standard Code for Design of Foundation Pit Engineering, the foundation pit enclosure is designed as a secondary foundation pit based on the geological and surrounding environment of the project. Bored cast-in-place piles with pile diameters of Φ 750 and Φ 900mm are used as retaining structures for foundation pit retaining structures, and the effective pile length is 15.9-23.4m; Φ 850 mm triaxial cement soil mixing piles with cement content of 20% and pile length of 12-14.5m are used for the seepage proof and water stop curtain around the foundation pit; The local pit bottom is reinforced with Φ 700 mm two shaft mixing piles, the cement content is 13%, and the reinforcement depth is 4 m below the pit bottom. Support system: a reinforced concrete support is set at the north and south ends of the project vertically, and the support center elevation is -5.6m (relative elevation). The support plane is arranged in the form of cross brace combined with side truss, and diagonal braces are set in local areas, and the concrete strength grade is C30; Φ 609mm steel pipes are used as diagonal bracing in other parts of the foundation pit,
