Internal Force Analysis of Circular Shaft Structures Considering Spatial Arching and Interlayer Shear Effects

To accurately investigate the stress and deformation behavior of support structures during mechanical shaft construction, this study proposes an analytical method for active earth pressure calculation based on limit equilibrium theory, incorporating both the radial variation of the circumferential stress coefficient and the spatial arching effect. Considering the entire sliding soil mass behind the shaft wall as the analytical object, the inclination angle of the sliding surface under active limit conditions is derived. Subsequently, by incorporating interlayer shear forces, a horizontal layer analysis is employed to establish the vertical and radial force equilibrium equations, leading to the formulation of an active earth pressure model for circular shafts. Furthermore, based on elastic mechanics theory, a corresponding method is developed to calculate the internal forces of the shaft structure. The theoretical predictions show good agreement with existing model test results and field monitoring data, demonstrating the accuracy and reliability of the proposed approach. The findings provide a theoretical basis for optimizing the design of circular shafts and assessing the structural stability of shaft walls.