Principles of Vibro Compaction
The method of soil improvement whereby granular soils are compacted using depth vibrators is known as Vibro Compaction or Vibroflotation. Naturally deposited soils as well as artificially reclaimed sands can be compacted to great depths. The current depth record lies at 70 meters for reclaimed sands and at 53 meters for naturally deposited sands. The intensity of compaction can be varied in order to achieve the desired effects depending on the foundation or ground improvement purpose.
- The sand and gravel particles rearrange into a denser state
- A significant increase in the horizontal to vertical effective stress ratio
- The permeability of the soil is significantly reduced
- Increased friction angle
- Settlements of the compacted soil mass (between 2% and 15%)
- Increased stiffness modulus
The compaction process consists of a flotation of the soil particles as a result of vibration, which then allows for a rearrangement of the particles into a denser state
Left: Loose, not yet compacted
Middle: In flotation
- Increased bearing capacity
- Settlement reduction under loads
- Near–elimination of differential settlements for large foundations
- Liquefaction mitigation
- Prevention of lateral spreading
- Prevention of settlements, due to rearrangement of particles from impacts
- Prevention of (inundation) settlements
- K-value reduction (permeability of soils)
Application of the technology in an optimal manner is an art!
The challenge of optimization lies in the multitude of parameters that can be varied and the narrow range in which those parameters need to be adjusted to deliver the desired results. Some of the parameters that can be varied include:
- Type of vibroflot used
- Distance between compaction points
- Hold time per depth interval
- Water pressure
- Location and type of water jets required
By vibration and the flushing of water and/or air, the vibroflot penetrates to the desired depth.
The vibroflot is recovered from a certain vertical distance after a verified holding time or buildup of resistance from the compacted ground.
Immediate top layers may be leveled or impact compacted or roller compacted to ensure a ready-to-build surface.
The following globally recognized projects, as well as many similar medium size projects were performed by the members of Betterground in either joint ventures or equipment supply and service arrangements.
Dubai: Palm Jumeirah, Palm Jebel Ali, Dubai Maritime City, Palm Deira, World Dubai Heart of Europe and Iceland (2004 and 2010), Pearl Jumeirah Island (2012), SARB Island (2013), Container Terminal 4 (2016)
Germany: Lausitz (eng. “Lusatia”) coal mine restoration slope stability projects (1994 to 2006)
Hong Kong: Chek Lap Kok Airport (1995), Central Reclamation (1994 and 2006), West Kowloon Reclamation (1991-1992),
Penny’s Bay (2001-2003)
Singapore: Pasir Panjang Container Terminal (1998 – 2000)
World Island Dubai: Vibro Compaction on the first showcase island. The completed island is seen on the right.
Dredged sand keys of land reclamations are compacted from barges before the filling of embankments and land based compaction of the final fill volume.