Vibroflotation I Ground Improvement Techniques

 Vibroflotation is a compaction method for soils that are performed by vibration. These are performed to compact the soils at a greater depth, unlike other compaction methods. 

Vibroflotation is defined as a ground improvement technique that strengthens the underlying soil by using a powered electrical or hydraulic probe called the Vibro-flot.  It is one of the oldest compaction methods developed in Germany (1930).

Procedure and Types of Vibroflotation Techniques

The process of vibroflotation is performed using a vibro-flot as shown in the below figure. Once the Vibro flot is inserted into the soil, it can work in three different ways to compact the poor soil.

Vibro-Flot in Vibroflotation Technique

Hence, the various techniques coming under vibroflotation are:

1. Vibro Compaction 
2. Vibro replacement
3. Vibro Displacement

1. Vibro Compaction

The Vibro-flot can start vibrating and undergo loosening and compacting of the soil in the surrounding area. The soil required for compaction is either obtained from nearby surroundings or supplied from the top. (Figure-2). This is called Vibro compaction.

Vibro Compaction Method of Soil Compaction

2. Vibro Replacement

The Vibro-flot has groves that spray air or water to the surrounding soil. The equipment can be penetrated into the soil by continuous flushing of air or water to replace the existing spray-poor soil. The soil that is completely replaced is filled using granular material, forming stone columns. This method is called Vibro Replacement. The granular material is fed from the top of the Vibro-flot equipment. As it is done in wet condition and the compacting material is fed from the top, it is called a wet top-feed method.

Vibro Replacement Technique of Soil Stabilization

3.  Vibro Displacement

The Vibro-flot whose tip is filled with granular material can be penetrated dry into the soil and once it reaches the bottom, the granular soil is poured by the simultaneous withdrawal of the Vibro-flot. Hence, it is a dry bottom-feed method.

Vibro Displacement Method of Soil Stabilization

Vibro Compaction Method	Vibro Replacement Method	Vibro Displacement Method
It is the process of densification of granular soil	In this process, the poor or inadequate soil material is flushed out using air and water and replaced with granular material forming stone columns. Used for clay and sandy soils. It is also called a wet top feed method.	In this process, the new material is transported to the tip of the vibrator and compacted using multiple displacement stages in a dry condition. Used in cohesive soils, were rearranging the soil is very tough.
Vibration method	Wet top-feed method	Dry bottom-feed method
Stable soil layer is formed.	Stone columns are formed	Stone columns are formed
Best for sandy soils	Used for clayey and sandy soils	Used in cohesive soils

Also Read: Difference between Subbase and Subgrade

Advantages of Vibroflotation in Construction

The main advantages of vibroflotation in construction are:

1. Reduce differential settlement
2. Fastest and easiest way to improve soil with weak bearing capacity.
3. Best choice to improve harbor bottoms.
4. Can be performed on existing structures
5. Does not harm the environment and nearby structures
6. No need for excavation
7. No water table issue
8. Reduce liquefaction during an earthquake
9. Reduce hazards and contamination of the soils.

Also Read : What is Soil Nailing in Construction? Principle and Methods