Deep compaction by vertical and horizontal vibration

By vertical vibration of a casing and addition of a cohesionless material, densification of fine sand is achieved in a similar way as by casing driving. Plugging of the casing occurs when the height of the sand column is approximately 10 times the inner diameter. Compaction of saturated sands can also be carried out by vertical vibration without any material addition using Franki Y probe. For fine and medium sands, the probing spacing can be larger as the soil is coarser. In unsaturated sand, the capillary cohesion due to the remaining humidity makes densification more difficult. The deciding parameter is the silt content. The minimum size of the vibrator can be derived from the initial cone resistance measured by CPT tests. Some tests suggest that with the presently available equipment, the vertical vibrocompaction with the Y probe performs better than the horizontal vibrocompaction by vibroflotation.