Improved limit analysis method of piled slopes considering the pile axial forces

For the analysis and design of piled slopes using the upper-bound limit analysis method, the axial force on the pile cross-section, where the pile is intersected by the slip surface, contributes to a resistant work rate of the pile; yet this has been omitted in past investigations. Based on analysis of the related work rate and energy dissipation rate of the piled slope, a closed-form solution to internal forces of the pile on the cross-section and some characteristic parameters of the critical slip surface under a specified factor of safety are provided with full consideration of the axial force. The calculation results for two examples show that the axial force has a possibly minor and non-conservative effect on the shear force and bending moment in some cases, but has a major effect on the location of the slip surface, which naturally causes additional design length of the pile. The existing methods without considering the axial force are less conservative or safer than the proposed method in terms of the requisite pile length, particularly under a smaller design factor of safety.