Vibro compaction is a ground improvement technique that densifies clean, cohesionless granular soils with a downhole vibrator. It’s a technique first developed by Keller in the 1930s and has been used on thousands of projects since.

Common uses

  • Reduce foundation settlement
  • Increase bearing capacity, allowing reduction in foundation size or width
  • Increasing stiffness
  • Increasing shear strength
  • Reduce permeability
  • Mitigate potential for liquefaction
  • Provide increased slope stability
  • Permits shallow footing construction
  • Very effective for sand compaction and land reclamation

Process

A vibrator hung from a crane is lowered into the ground with penetration usually helped by water jetting. The energy from the vibration reduces the inter-granular forces between the soil particles, making them denser as the vibrator is raised in lifts. Sand backfill is then poured in from ground level to compensate for any decrease in soil volumes. More backfill is added and compacted and the vibrator is gradually removed until it has built up to ground level.

The required treatment depth is designed for each project and is typically in the range of 5-15m with a maximum depth of 40m.

Vibro rigs are fully instrumented with an on-board data acquisition system. Data from the system, such as amperage and lift rate, can then be recorded and displayed in real-time alongside specified target values on an in-cab monitor. This monitoring allows the operator to correct any deviations in real-time during the construction process to keep the vibro compaction within project specifications.

Advantages

  • A versatile ground-improvement method that can be adjusted to a wide variety of soil conditions and foundation requirements
  • Offers an economical solution for ground improvement
  • Relatively quick execution so subsequent structural works can follow very quickly
  • Soil improvement enables standard shallow footings which can lead to savings
  • Environmentally-friendly as uses natural and in situ materials
  • Extremely quiet with low vibration
  • Only a small quantity of soil has to be removed during the process so avoids the cost of spoil removal associated with continous flight auger and bored piling systems

Quality assurance

The vibro equipment used is designed and manufactured by Keller's in-house equipment manufacturer exclusively for use by Keller companies.

In-house quality production management software enables Keller to capture and analyse data in real time and valid the performance of the ground improvement being carried out.

A variety of production parameters are generally logged during execution including depth, current, pull down force, uplift/pull down sequence, time and date and element number.

Field trials can also be used to verify column production parameters, along with static load tests (single or group), column material compressive strength tests, and column diameter verification.