Compression Rings

A compression ring shaft is constructed by installing vertically drilled interlocking concrete holes in a circular pattern. The shaft is held together in compression due to confinement pressure from the retained soil and the compression forces are resisted by high strength concrete.

Advantages of compression ring shafts:

  • No internal bracing required
  • Reduced material usage with no steel reinforcing requirements at shallower design depths
  • No interference with other construction trades – excavation can begin and can be expedited once vertical drilling is complete
  • Improved control of groundwater and water tight construction

Challenges associated with compression ring shafts:

  • Drilling tolerances are strict as design interlock is critical. A guide wall is required to ensure vertical construction tolerances are maintained