Coupled hydromechanical modelling of cone penetration in layered liquefiable soils

Abstract

Soil layering modifies cone penetration measurements when the cone is close to layer boundaries. Transition zone and thin-layer effects appear, complicating interpretation. To help identify the mechanisms underlying transition and thin-layer effects, several series of realistic simulations of cone penetration in layered soils are presented. Cone penetration tests are simulated using fully coupled hydromechanical models solved with the particle finite-element method. A constitutive model capable of representing flow liquefaction is employed to explore the effect of embedded layers with different initial state parameter and/or hydraulic conductivity than the host soil. Sensing and development distances for tip resistance and excess pore pressure are examined, as well as the effect of layering on dissipation tests. It is shown how distortion of layer interfaces by the cone is captured, explaining several characteristics of pore pressure and dissipation records. It is also shown that looser soil states may be hidden in the tip resistance trace by simultaneous changes in soil hydraulic conductivity.