Supporting characteristics of deep foundation pits using reinforced concrete support to replace steel support

In order to control the stability and construction impact on the surrounding environment in foundation pit engineering, the administrative departments in charge of construction in some provinces in China require that the first support in deep foundation pits must use reinforced concrete bracing. To study the deformation characters using reinforced concrete to replace steel support, Shenzhen subway foundation pit is taken as an example. The finite element software ABAQUS is used to simulate the influence of the stiffness attenuation of bracings system on the surrounding structure during the excavation process．In the finite element analysis process, the Mohr-Coulomb elastic-plastic model is applied to soil，and nonlinear contact analysis is set up between the enclosure wall and the soil. Considering the spacing position of the reinforced concrete bracings, both rules of the horizontal displacement of enclosure wall and the bracing axial force are analyzed at different excavation stages. The result shows that the first support using reinforced concrete bracing or steel bracing in deep foundation pits have no obvious effect on deformation. But according to the deformation of deep foundation pits the central reinforced concrete supports can reduce deformation and bending moment of the retaining structure.