Research on redundancy design of the transition section of composite pit support in the foundation pit of the Xingong Station of the Beijing subway

Numerical simulation methods are used to simulate the whole process of construction of the foundation pit in the foundation pit project of the Xingong Station of Beijing Metro Line 19. Under the assumption that the composite support structure partially fails, the structural deformation and force conditions are taken as the criteria, and the redundancy of the composite support structure is calculated and optimized. The results show that (1) in the case of partial destruction of the supporting structure, the deformation of the piles at the transition section of the composite support system increases significantly; in the case of the waist beam, the deformation of the pile is well controlled. (2) After the partial damage occurs, the structure joins the waist beam, which increases the force transmission path of the structure, and the internal force redistribution of the entire structure is more uniform and reasonable, which can effectively prevent the stress concentration and ensure the safety and stability of the structure; (3) In the two failure modes, adding the waist beam to the support structure significant increases the structural redundancy, and the effect of the concrete waist beam on the structural redundancy is better than that of the steel waist beam. In practical projects, the addition of waist beam is of important significance in improving the stability and redundancy of support structures, and the design and application of the waist beam should be emphasized.