The incremental method based onthe beam finite element method is commonly used for calculating foundation pitenclosure structures. However

there is a lack of research on the dynamicdecrease of soil spring stiffness in the passive zone during excavation

whichleads to soil resistance softening. This paper introduces two stiffnessvariation coefficients to quantify the dynamic change of soil spring parametersin the passive zone and establishes an incremental method for calculatingfoundation pit enclosure structures based on this process. For nonlinearfoundation models

a refined incremental method is proposed for numericalcalculations. Three basic soil spring models (linear elastic

idealelastic-perfectly plastic

and hyperbolic) are used to obtain the softening p-y curves in the passive zone. A comparison of these models shows that thevariation curve of the equivalent horizontal resistance coefficient obtainedusing the hyperbolic soil spring model aligns better with actual observations.An engineering example demonstrates that the calculation results based on thehyperbolic soil spring model correspond better to measured wall displacementsat different excavation stages. Parameter analysis highlights the significantinfluence of the stiffness variation coefficient related to the ultimate resistance pu of thesoil in the passive zone. Therefore

when using the proposed method

carefulattention should be given to calculating the ultimate resistance pu and the influence ofexcavation on it in the passive area should be considered.