Middlemore Station Pedestrian Crossing
Sector: Bored Piles, Reinforced Concrete Piles
Location: Otahuhu
Client: Downer NZ
As part of the Wiri to Quay Park Third Main Line project Middlemore Station is being upgraded, requiring the construction of two new pedestrian overbridges. Spiral Drillers were contracted to Downer NZ to undertake the piling, including 750mm to 1200mm diameter piles ranging from 14 metres to 26 metres in depth.
The works were undertaken in close proximity to a live rail line, resulting in careful planning and diligent approach to work with rail exclusion areas. The main car park facility for the hospital was right next to the work site with large numbers of pedestrians viewing the site throughout. This also meant that deliveries were required to be completed through the night and piling during the day to avoid unnecessary congestion in the access roads.
Spiral Drillers proposed constructing the piles under a polymer support fluid given the sensitive infrastructure and vibration restrictions in the area. The support fluid plant catered for all of the piles with stable bores throughout and enabled the concrete to form against insitu ground for the skin friction requirements by design.
Upon completion of the pile, a short cage was plunged into the top of the fresh concrete and aligned in position to form the columns of the bridge structure. Collaboration with the other contractors on site to achieve a tight tolerance enabled the bridge deck units to be pre cast and speed up the construction programme.
Other piles on the job included 4 lift shaft piles where a proposal to complete the piles by dead drilling several metres to avoid a large excavation to bring the piling rig down to the top of pile level was utilised. All piles on the project underwent low strain integrity testing in the form of Pile Integrity Testing, where the results for the piles were presented in a report.