Caisson Foundations

Caissons

Caissons are often used in marine construction to reduce the amount of work undertaken in the water.  These massive blocks can have a wide variation in foundation requirements, from a level tolerance of ±5mm to ±500mm after settlement depending on the purpose of the structure and the ability of later construction stages to absorb this tolerance.

Stone bedding layers are often used as the foundation. This creates certain challenges when constructed underwater, such as:

  • Difficult to level
  • Liable to settlement
  • Risk of washout and scour

Grouted Foundations

Compared to stone bedding layers, grout bag foundations are well suited to applications where:

  • Construction tolerance is tight
  • Settlement is undesirable
  • There is a risk of stone washout or scour during or after construction
  • When accurate stone levelling is not practical
  • When working on a rock bed
  • In seismic zones

Installation

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Foundation grout bags are specifically developed with the designer and contractor for each project’s particular requirements. Our engineers use a range of variables, not limited to:

  • Bed tolerance
  • Caisson level tolerance
  • Initial stability requirements
  • Shear transfer
  • Uplift limits
  • Transport distances
  • Working environment
  • Installation windows

The formwork and grouting pipes are prefixed to the concrete element in the casing yard. The element is then submerged and positioned on jacks, the bags are pump filled from a grouting barge. The formwork controls the grout, filling the void between the element and the bed surface in a carefully designed sequence. We guarantee void filling and full contact with controlled uplift pressures.

Advantages

Foundation grout bags provide control during construction by:

  • Achieving tight construction tolerances and little settlement
  • Absorbing large bed tolerances
  • Eliminating the risk of washout
  • Initial stability where required,
  • Even distribution over the caisson base
  • Eliminating requirement for stone layers when working on rock

Performance has been demonstrated by 30 years of proven performance on some of the world’s largest marine construction projects.