Study on Synthesis Stiffness of Inner Supported Deep Excavation in Soft Soil Area

Abstract

The horizontal displacement of retaining structure is particularly associated with synthesis stiffness of support system. The synthesis stiffness of support system is highly interrelated with three parts including the retaining wall, the inner brace and the soil at bottom of excavation. In order to estimate the lateral movement of retaining wall, a synthesis stiffness formula is been proposed. The proposed model concludes a variety of factors, such as horizontal flexural rigidity of retaining wall, compressional stiffness of inner brace, average vertical support spacing, average horizontal support spacing, depth of wall penetration and stiffness of the soil below final excavation depth. Comparing with the Clough synthesis stiffness, more factors is been considered. Comparing with the MVSS synthesis stiffness, the factor of soil below final excavation is been defined exactly. After that, finite element method is employed to calculate the maximal lateral displacement of the retaining wall. And a good relationship is established between maximal horizontal displacement and synthesis stiffness formula. Finally, the calculations are used to compare with the observed data from several deep excavations, the result validates the applicability of proposed model. The research provides a new method for describing the comprehensive stiffness of support system of foundation pit. It is convenient to estimate the maximum horizontal displacement of the retaining structure at the design stage and to select the support system quickly.