Evaluation of Soil Mixing at various depths using Generalized Interpolation Material Point Method

Department of Civil Engineering, Aalto University, Espoo, Finland

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Abstract

Deep Soil Mixing has been widely applied in Nordic countries, Japan and other countries to improve the strength and stiffness of in-situ soil. However, the mechanical variability of stabilised soil remains a major issue and quantifying the effects of operational parameters such as blade size, filling level, and rotational speed is difficult because the internal soil flow during mixing cannot be directly observed. This study clarifies depth-dependent deformation mechanisms during mixing through three-dimensional numerical simulations in Uintah using the Generalized Interpolation Material Point method. Calculations reproduce the behaviour of high-water-content kaolin clay with an enhanced, strain-rate dependent, Mohr-Coulomb model. The simulations indicate that soil kinematics are strongly depth-dependent, with peak velocities concentrated near the blade region and rapidly decaying upward and downward, resulting in a limited axial influence zone and persistent mixing heterogeneity. At each depth, the velocity distribution is approximately normally distributed, enabling statistical characterisation of the mixing state and providing a quantitative basis for evaluating operational effects.