Field measurements and numerical analysis of vibroflotation of sand

Vibroflotation is an established ground improvement technique for granular materials. It densifies loose sands by means of shear and compressive deformation processes imparted by the horizontal vibrations of a vibrator probe at the required soil depth. The field experience and empirical relations used for the design of vibroflotation processes prompt further study and analysis. Numerical simulations of the method help provide insight into the process. A coupled Eulerian–Lagrangian framework was used to model the compaction process. The compaction process was modelled based on the pilgrim step method for a depth range from 25 m to 10 m. A hypoplastic constitutive model was used to characterise the stress–strain behaviour of the fine sand. Numerical results were validated against in-field cone penetration test measurements made before and after the compaction of fine sand in east Germany. The validation was followed by a parametric study in which the following were evaluated in terms of their effects on the extent and degree of compaction: frequency, relative density, shape of vibrator, spacing of compaction points, nature of compaction process and type of sand.