Research on Radial Equivalent Stiffness Coefficient of Ring Beam in Cylindrical Deep Excavation

The flexibility fulcrum method is the calculation method of the retaining structures of deep excavations, which is recommended by Chinese current codes. Based on the flexibility fulcrum method, a definite calculation method is proposed for calculating the fulcrum coefficients of ring beams as the flexibility fulcrum of retaining piles in cylindrical deep excavations. The purpose of this method is to calculate the displacement and the inner force of the retaining structures more reasonably. According to the thick-walled cylinder theory of plastoelasticity, the radial displacement formula of the ring beam is obtained. Then the radial equivalent stiffness coefficient of the ring beam is obtained by using the radial displacement formula based on the definition of the stiffness coefficient. The radial equivalent stiffness coefficient and equivalent compressive capacity of the ring beam are using as parameters of flexibility fulcrums to calculate the displacement and inner force of retaining structures. This method is used to calculate some cylindrical deep excavation project in Shenyang, China. The results indicate that: the results calculated by using the radial equivalent stiffness coefficient of 2d flexibility fulcrum method are in good agreement with the field monitoring data, safer than the 3D finite element calculation results, and more reasonable and economical than the usual stiffness coefficient results.