The original BNZ building in Petone, NZ, required seismic strengthening. There are following issues before pilling
Geological Issues:
- Presence of liquefiable strata, piles lengths are limited to avoid loss of foundation strength due to liquefaction.
- Presence of artesian aquifer in the deeper depth, deep piles extending to this depth is not desirable caused by huge resource cost and increased difficulty of drilling into the aquifer.
- The foundation of building may be effected by natural force, for example tidal influences
- Liquefaction risk of some layers of ground during an Ultimate State Limit (USL) earthquake, such as the medium dense sand layers
Structural Issues:
- Existing building means space limitation inside building, there are limited pile layout options
- Access limitations into the existing building leads to large equipment and machinery may not be possible
- It may difficult control return grout due to existing foundations for instance there is a gap between floor level and ground level.
The CCS JETPILEs were identified as the only suitable choice based on performance, constructability, and cost.
- 19 piles overall
- Diameter 450mm with a diameter 323mm Reinforcing Tube to 5m BGL
- 7.5m typical depth – above the Waiwhetu Aquifer and liquefaction layers
- All access through standard double door and stairs
- All piles installed and tested through diameter 500mm core holes through existing slab