The application of a significant additional load induces soil deformation around the pile

generating a downward drag force

commonly referred to as negative skin friction. This phenomenon significantly reduces the pile's ultimate axial load capacity. Therefore

precise estimation of negative skin friction is crucial for pile design. To accurately calculate the negative skin friction acting on the pile

it is essential to determine the stress states at the pile-soil interface under varying soil deformations. However

many existing methodologies solely consider peak or residual stresses on the shear plane

neglecting the process of stress changes in soil deformation. This approach often results in an overestimation of negative skin friction. In this investigation

we propose a novel method for calculating negative skin friction that comprehensively accounts for the whole process of stress state alterations occurring during soil deformation (pre-failure zone and peak stress

post-failure zone and residual stress state) and describes the relationship between soil deformation and stress using a hyperbolic mechanical model. On this basis

soil deformation behavior is classified into three distinct forms. The spatial distribution characteristics for negative skin friction were then explored individually for each form. Additionally

the influence of different soil parameters on the spatial distribution of negative skin friction was also investigated. Finally

the accuracy and applicability of the new negative skin friction calculation method is validated through comparison with field measurement data. It can be used as a reference for practical engineering.