Study Of In-situ Monitoring Of Deformation Law Of Deep Excavation In Weiqu South Station Of Xi’an Subway Line

One of the key problems in the subway construction is the design and the stabilityanalysis of the retaining structure of station deep foundation pit, Xi’an Metro deep foundationpit deformation monitoring research has important engineering application value. Based onthe deep foundation pit of subway station in Xi’an Weiqu South Station as the background, itstudied with the method of theoretical analysis, in-situ monitoring and numerical simulation.The main conclusions as follows:(1)It studied on deformation mechanism of the deep foundation pit, and analyzed themain factors affecting the deformation of deep foundation pit. Deep foundation pitdeformation mainly includes the retaining wall deformation, the bottom heave of the pit andground surface deformation; the main influencing factors of subway station deep foundationpit deformation is divided into natural factors, design factors and construction factors.(2) According to the geological conditions and groundwater burial conditions, combiningwith the main type of construction, it designs deep foundation pit dewatering program inWeiqu South Station. The deep excavation is dewatered by tube well points, and it layoutsdewatering wells by the pit and precipitation observation wells in the pit.(3)The monitoring plan of construction of subway station deep foundation pit wasdesigned, the monitoring work was completed. The horizontal displacement of the pile, steelsupport axial force variation and ground settlement around deep excavation made a keyanalysis. The results show that the pile displacement, especially the horizontal displacementof pile top can be used as important index to evaluate the safety condition of the retainingstructure, steel support have obvious restricting effects for deformation of foundation pit. Themonitoring results show, enclosure structure design scheme and monitoring scheme were reasonable, which ensure that the excavation in the construction process of stability.(4)It used FLAC3D software to simulation of the excavation process of deep foundationpit, horizontal displacement of supporting pile, steel support axial force of foundation pit andthe surrounding ground settlement calculation results and the actual monitoring results underfour kinds condition were compared, they were in good agreement.