Hefei Subway Station Within Deep Foundation Support Optimized Design

With the rapid development of urban construction, the number of high-rise buildings, subway stations and other projects increased day by day, and the complexity, area and depth of the foundation excavation were increased. The selection of the retaining and protection scheme and design parameters can directly affect the stability, economy and reasonably of excavation. The design of the retaining and protection structure should both meet the requirement of strength, stability and deformation and ensure the safety of the surrounding environment. In addition, an economic and technical plan should be determined with the consideration of construction schedule, materials, equipment and environment protection.Bored pile with steel-tube bracing retaining and protection plan was employed in subway station deep foundation excavation project. Three steel-tube bracings were set in the envelope and six steel lattice columns were set in the north and south ends of the well location. The insufficient length of the same layer support spacing between the upper and lower elevation and the installation of vertical support cannot meet the requirement of the large-scale construction machinery at the construction site. If construction machinery was employed, the conflict with the strut erection process is inevitable, which will provide inconvenience to the excavation and the construction of the following main project.This study was focused on the design of the tenders Road, Hefei first line subway station deep foundation excavation project. Take the engineering geology, hydrogeology, surrounding environmental conditions and the features of a variety of deep foundation excavation retaining and protection forms into consideration, two optimized retaining and protection plans without strut (bored piles and prestressed anchor cable retaining and protection program and double row piles wall and prestressed anchor cable retaining and protection program) were designed by using software. Compared with the original plan at aspects of security, stability, deformation, cost and construction schedule, bored piles and prestressed anchor cable retaining and protection program is more suitable. The design of retaining and protection scheme and its applications can give reference to other deep foundation excavation projects.