Variation of axial force of steel struts in deep excavations

The discrete data and unclear variation trend of axial force of steel structs are the important design problems, which seriously affect the safety and economic rationality of deep excavations. A three-dimensional finite element model for a deep soft excavation in Nanjing Metro station is established to study the variation of axial force of steel struts. Based on the monitoring data in the process of excavation, the dual-combination method for the axial forces of steel struts and wall deflection is put forward to validate the rationality of the model and parameters. The correlation between the wall deflection and the axial force of steel struts during is excavation revealed. Then, the influences of single- and double-axial preloading on the axial forces of steel structs, wall deflection and moment are studied to propose the basic requirements of using the preloading axial force technology to control deformation. The influences of struct erection conditions are studied to expound the reason of the discrete measured values of axial force of steel struts and the important influences of over-excavation on the safety of engineering, and to reveal the research significance of hanging steel struct erection. The research results may provide a new direction for the development of deformation control technology of deep excavations in thick soft soils.