Stability Analysis of Removal of Steel Supports in Variable-Section Pits

In order to analyse the changes in pit stability caused by the removal of steel support and solid casting of a variable section pit, this paper carried out the whole process of numerical simulation of the selected section pit construction using ABAQUS, introduced a redundancy evaluation method based on the growth rate of deformation, calculated the stable state of the supporting structure, assessed the de-supporting state under two de-supporting design schemes—laminar and stepped—and carried out the stability analysis of the two schemes. Finally, the characteristics of pit stability changes under the state of de-supporting in the variable cross-section area were obtained. The results show that the stepped backfill and de-propping scheme provides better stability control than the laminated scheme, the minimum redundancy Rmin in the key variable section area increases by 0.03 on average, the minimum relative deformation Pmin decreases by 5% on average, and the maximum local improvement is 10.52%. The stepped scheme shows the most significant improvement in redundancy at the distal end of the reduced section, and the overall deformation response is more homogeneous. The study verifies the applicability of the redundancy analysis method in evaluating variable cross-section pit bracing, which is of great engineering significance for the optimisation of pit bracing design under similar structural conditions.