Application of Flexible Retaining with Prestressed Anchor to Reduce the Effect that Excavations have on Urban Environment.

The rigid retaining methods of a deep foundation pit have several disadvantages, including high cost and lengthy construction periods, and the noise and mud generated during the construction process seriously affect the nearby urban environment. Soil nailing cannot be used in deep foundation and it is a passive retaining method and cannot adequately control deformation. Anchor shotcrete with a prestressed anchor may cause punching failure in the surface because of the large pre-stress. Therefore, prestressed anchor retaining with bearing structure under anchor head (BSUAH) is proposed for stabilizing the walls of a pit. It is different from conventional anchor shotcrete retaining as it uses a special bearing structure under an anchor head. It can substitute rigid retaining method and use in deep foundation pit. This research used FEM software (Midas/GTS) to analyze the three types of BSUAH with shotcrete: no-constraint, semiconstraint and full-constraint. And a field tests of the prestressed anchor retaining were performed in the Xintiandi project in Dalian China. The results show that the prestressed anchor retaining can effectively control deformation of a deep foundation pit, indicating that this method is suitable for stabilization applications of deep foundations pits. Compared with the pile, the noise and mud pollution in the prestressed anchor retaining construction is less, which is beneficial to protect the surrounding environment. [ABSTRACT FROM AUTHOR]