A modified mechanical modeling of pipe-soil lateral/axial interactions incorporating pipe trajectory and contact surface characteristics

Accurately predicting pipeline mechanical behavior under ground movement relies on the precise determination of the Soil Resistance-Pipe Displacement (SR-PD) curve. Standard formulas, however, face significant challenges, including the omission of softening behavior after peak resistance, underestimation of ultimate resistance, and neglect of the non-uniform resistance distribution across the pipe cross-section. To overcome these challenges, this paper incorporates the Modified Mohr-Coulomb model and direct shear test data to characterize the behavior of sandy soil at the pipe-soil interface. A logarithmic spiral curve is employed to define the pipe’s trajectory in sandy soil, enabling an analysis of the stress state of the “pipe-wedge” structure during the elastic, hardening, and softening stages of sandy soil deformation. Three models are developed: MPSIM-L, which analyzes lateral resistances along the trajectory; MPSIM-A, which accounts for contributions of soil pressure, sand dilatancy, and cohesion to axial resistances; and MPSIM-LRD, which applies the finite difference method to calculate soil pressures at various locations within the pipe cross-section. The findings show that MPSIM-A and MPSIM-L reduce errors in predicting ultimate resistance by approximately 50% and 38.5%, respectively. Additionally, the resistance distribution predicted by MPSIM-LRD closely aligns with experimental data, demonstrating the accuracy and reliability of the modified models.