Foundation UnderpinningPiers and Reinforcement
Piers and foundation works
The practice of underpinning small-to-moderate sized structures to repair foundation settlement and loss of support is a common engineering endeavour that is seldom discussed, or documented in structural reports or work records. But underpinning is a global problem that affects residential developments.
The most critical element of nearly all underpinning works is the physical construction and stability of the piers.To attain an adequate load capacity, the piers generally have to be founded on firm soil strata that are beneath the weaker or unstable soils that called for the underpinning in the first place. Ref: When Retaining Walls Come Tumbling Down P.332
When Retaining Walls Come Tumbling Down
Author: Alan Davis
Screw piers being placed to support retaining wall.
Note PVC pipe for headstock.
Screw piers were not suitable for this site due to salt water exposure. PVC concrete filled popes were used four metres deep.
Unit foundation failure, photograph shows excavator doing prep works before screw piers were placed.