Vibrocompaction

Vibrocompaction is a ground improvement technique used to densify loose granular soils in situ by applying controlled vibration with a specialized probe. The term covers two main approaches: vibroflotation (or vibrocompaction via vibration) and vibro-replacement (where gravel or crushed stone is introduced to form dense columns).

In vibroflotation, a vibrating steel probe is driven into the soil from a crane or drivable rig. The vibration, combined with the probe’s weight, mobilizes the soil grains and allows fines to drain, encouraging the surrounding soil to rearrange into a denser configuration as the probe is gradually withdrawn in passes.

In vibro-replacement, the soil around the penetrating probe is gradually displaced by compacted aggregate, forming a dense column that provides higher bearing capacity and reduced settlements than the surrounding ground.

Typical applications include foundations for buildings, bridges, and embankments on loose sands and gravels, backfill under retaining structures, and pre-improvement prior to excavation. It is most effective in non-cohesive soils with relatively low fines content and limited groundwater flow; clays or silty materials are generally not suitable without additional measures.

Equipment commonly consists of a vibroflot connected to a hydraulic or diesel power unit, with a guiding casing to control penetration. Water, bentonite, or cement slurry may be used to aid insertion and stabilization. Performance depends on soil conditions, installation depth, and the number of passes.

Limitations include reduced effectiveness in cohesive soils, potential disturbances to adjacent structures from vibration, and the need for favorable drainage pathways. Proper design and quality control are essential to achieve the intended increases in bearing capacity and reduction of settlements.