Vibro Compaction

Vibro compaction is an established technique for stabilising granular soils such as loose sands, gravels and some hydraulic fills using vibroflots.

How vibro compaction works

The offset position of the eccentric weight housed in the vibroflot creates a horizontal vibratory action, which acts to compact loose granular soils (i.e. sand and gravels) into a denser condition, thus providing a significant improvement in the geotechnical properties of the treated ground.

On reaching the required design depth water jetting from the nose cone is reduced, and the vibroflot is slowly extracted with pauses at regular intervals to ensure satisfactory levels of compaction are achieved at each depth. Additional side water jets are often utilised to assist with compaction and to encourage further erosion of the soils around the bore.

The vibroflot is gradually withdrawn back to the surface where a zone of compacted ground is formed around the insertion point. Additional site won sand may also be added at the top of the hole to fill the cone of depression that is formed. The rate of extraction is varied to suit the conditions encountered on site and to ensure that the correct amount of densification is achieved for each project.

Benefits

• Vibro compaction techniques are extremely well established and in suitable soil types can be used for construction of tank farms, ports and marine structures
• Vibro compaction is extremely effective for sand compaction, and to date BBGE has utilised the technique in the Middle East, North America and the Mediterranean
• Vibro compaction can provide fast, in-situ densification of loose sands to depths of up to 30 metres and is one of the most economical and sustainable ground improvement methods available
• Vibro compaction significantly reduces the threat of liquefaction in the event of seismic shock