Investigating soil-pipe interaction in dense sand: a numerical study using Cosserat continuum theory

Soil–pipe interaction is a critical consideration in the design and performance assessment of buried infrastructure, particularly under significant soil deformation. Modelling such interactions in dense sand—which exhibits pronounced strain-softening behaviour—poses considerable challenges due to mesh distortion and mesh-dependency issues inherent in traditional continuum-based numerical methods. This paper presents an innovative approach, the Cosserat-based Particle-Cell Hybrid (Cos-PCH) method, to investigate lateral pipe movement in dense sand. The Cos-PCH framework integrates the large-deformation capabilities of the Particle-Cell Hybrid technique with Cosserat continuum theory, incorporating an internal length scale to regularise strain-softening behaviour and ensure mesh-independent results. Validation against experimental data confirms the robustness of the proposed method. The validated model is then employed to systematically analyse lateral pipe movement, with emphasis on the influence of internal length scale, softening behaviour, and frictional-dilative characteristics on both peak and residual resistance forces, as well as associated failure mechanisms in the surrounding soil. This study provides valuable insights into soil–pipe interaction and contributes to enhanced predictive modelling in geotechnical engineering.