Architect: Curious Practice

Builder: GTS

Engineer: Izzat Consulting Engineers

Heavy Foundations were engaged by GTS Constructions to provide the contiguous pile walls and foundation piles for a residence in Newcastle East. 

The site had a few complexities which made the job challenging, these included:

- An overall site width of less than 6m. Excavators could not move past each other and needed to be positioned and strategically coordinated to ensure efficiency and continuous flow of work. 

- Tight working areas amplified the interplay between the new build and existing neighbouring structures. Steep banks on the existing ground levels caused some constructability issues with the proposed finished height of contiguous pile walls being much lower or higher than neighbouring land at steps. In some spots temporary lightweight shoring walls were required above the structural wall to prevent sand migration. 

- Due to the age of the properties in the area, typically founded on bricks or shallow footings, extreme caution was taken not to undermine these properties. Careful thought was given to staging the bored piers and not fully excavate a section without some support being in place.

- Hard rock outcrops at the front of the site made for tedious drilling.

The first stage of works was completion of the wall piles on the northern and southern boundaries of the job. Due to the reach of the excavator, the furthest pile that could be completed from the top was about a third of the way down. Completing these piles within our desired tolerances was tedious work. Pushed by the steep bank, burried structures and hard rock the auger had a tendency to want to creep down the hill. 

The second stage of the job was to tie in the back wall which ran from the north to south boundary. For this section, where less reach was required, we were able to float in our masted rig and drill to our tolerances much more efficiently than using the excavator. 

The rig needs a level platform to work off at approximately the same height as the finishing height of the pile. We had to make some special decisions about how to setup and maintain this platform with a support excavator to move the drilled spoil, create batters and feed reinforcement cages with very limited movement either side of the rig. 

The last stage of the retaining wall piling was the lowest section. These were completed using the excavator from the bottom of the hill. The spoil that was generated from drilling the side and top piles was used to build a ramp that would allow us to take the excavator from the top of the job to the bottom. This ramp was then also used to assist in reaching up the hill to finish the remaining piles on both boundaries.