Ultimate bearing capacity of a pipeline on clayey soils: Slip-line field solution and FEM simulation

Abstract

The ultimate bearing capacity of a cylindrical foundation (e.g. a submarine pipeline, circular mooring lines) on clayey soils is analyzed analytically and numerically by employing the slip-line field theory and the plane-strain finite element method respectively. A slip-line field solution is presented, taking into account of circular configuration of the pipe, the pipe embedment, and the pipe–soil interfacial cohesion. The derived bearing capacity factors for a smooth rigid pipe may limit to those for the conventional rectangle-shaped strip footing while the pipe embedment is approaching zero. A plane-strain finite element model is further proposed to simulate the quasi-static process of the pipeline penetrating into the clay soil, in which the contact-pair algorithm and adaptive meshing technique are employed, and the Drucker–Prager constitutive model is used for modeling the soil plasticity. Comparison indicates that the present numerical results match well with the derived slip-line solutions. According to the obtained vertical load–displacement curves, concurrently referring to the plastic strain field and the soil incremental-displacement vector field, the shear failure types and the corresponding collapse loads can be thereby determined for the pipeline foundations on clayey soils.