Stresses and deformations of support structures of deep foundation pit based on centrifuge and numerical simulation

Based on the actual characteristics of excavation and support structures of foundation pit, a suitable centrifugal model test scheme is obtained, and the centrifugal model test is used to analyze the distribution characteristics of stress and deformation of the support structures of the ultra-deep foundation pit during the excavation process. Simultaneously a three-dimensional finite element model is established to simulate the deformation of the support structures during the excavation process of a circular foundation pit, and the test and numerical results are compared and analyzed. The results show that the horizontal displacement mode of the support structures is the "bulge shaped deformation" with small ends and large middle. As the depth of the foundation pit increases, the point with the maximum horizontal displacement of the underground diaphragm wall gradually moves downwards. The surface settlement is in the form of grooves, and as excavation continues, the bottom of the settlement groove develops towards the direction away from the foundation pit. The variation of soil pressure behind the diaphragm wall is non-linear. At the early stage of excavation, the variation of soil pressure along depth is small, but as excavation continues, the variation of soil pressure gradually increases. As the excavation continues, the bending moment value gradually increases, reaching the maximum positive bending moment near the depth of 17 m, about 2200 kN·m/m. The deformation characteristics of the support structures obtained from the numerical analysis and centrifugal model tests are relatively similar. The research results contribute to providing scientific basis for proposing practical and effective protection measures of the support structures for excavation of foundation pits.