The Impact On The Surrounding Buildings In Deep Foundation Pit Excavation In Sensitive Environments

Stability of freezing wall is the main security issue in freezing shaft construction with deep alluvium, therefore the stability study of freezing wall is of great significance to freezing shaft sinking process. Many stability analysis models about freezing wall before and after wall masonry have been studied over years, but most of their main points are the interactions between freezing wall and shaft lining instead of the foams between them. As an independent structure, the foam significantly changed the interaction between outer wall and freezing wall at the pouring period and the early growth rate of freezing pressure. With indoor experiments, theoretical analysis and field monitoring, this paper explores the interactions of freezing wall, shaft lining and foam under the background of the mine shaft in Gu-Bei, Huainan.Research of physic-mechanical properties of frozen earth and foam was made in indoor experiments. The result shows that the compressive strength, elasticity modulus and Poisson ratio of frozen earth scales linearly with temperature. The paper draws a creep regression equation with the creep parameters. The experiments of polystyrene foam board include uniaxial compression tests and uniaxial creep tests, which show that there are three stages of foam’s compression, linear deformation, curve deformation and rigid. Each of the stages plays different roles to freezing wall. With the viscoelastic plasticity of freezing wall and the rheological model, theoretical analysis creates the design formulas of freezing wall’s freezing pressure for the three stages. The change rules by time of the freezing wall’s force are obtained with the field monitoring of freezing pressure, ring and longitudinal carring bars. Results show that for stabilizing the creep freezing wall, the foam not only reduces the freezing pressure of outer wall, but also decreases the rate of the pressure.