27 October, 2007

Piles aren't just piles!!

My first job was as a trainee mechanical engineer at BHP (a short lived career) and ever since I think I’ve been a frustrated engineer at heart. My daily visits to the NCV site always throw up new things at which I can to marvel. The piling technique being used for the NCV has been chosen due to the very sandy ground on site. The Continuous Flight Auger (CFA) piles (also known as Groutcrete piles) are a non-displacement pile used where fast vibration free installation is required in difficult ground conditions. The drilling process is unaffected by ground water or collapsing soil conditions. The company completing the work is Advanced Foundation Solutions.

The pile is formed by first drilling into the ground with a continuous flight auger. Cement-sand grout or concrete is then injected under pressure through the auger's hollow stem as it is being withdrawn. On completion of this operation, a reinforcing cage is pushed into the fluid column of grout or concrete. Equipment is available to install piles up to 32 metres long but the NCV piles are generally about 10 metres in length. The diagram below shows the key stages in the process, including drilling, pumping the concrete into the hole as the augur is extracted and insertion of the steel reinforcing. For the more technically minded check out this link.

The building requires 170 of these piles and a skilled operating team can complete 10-15 per day when things go well. The first week of drilling had some dramas with teething problems getting the concrete mix right and the machine set. A major breakdown meant that the machine needed to be replaced and a full day was lost. The operators are confident that they can make up for the lost time. Our sandy soil has helped with no time lost this week due to rain. Lipman hopes to see Stage 1 of the piling completed by the end of next week with a second stage of piling slightly later for the non-basement section of the building. The picture below shows the AFP drill on the NCV site drilling on the Anzac Parade side of the building.


20 October, 2007

Under the New College Big Top

Progress continues to be good with the NCV. There have been a number of first in the last week:

* The Big Top was pitched (well it looks like one!).
* The first concrete was poured.
* The first piers were put down.

The movement of soil (more like sand) around the site continues mainly due to a change in the method for drilling the piers an extra metre of sand was taken out to allow pier caps to be constructed then back-filled. As a result a great mountain of sand will need to stay on site for the next 4-5 weeks. This has presented challenges for the contractors but this is the only practical thing to do. In order to control dust Lipman has chosen to cover the mound to spare the neighbours and students waiting for buses on Anzac Parade.


09 October, 2007

Foundations set to begin

Great progress being made

Progress has been good with the building. Bulk excavation is completed, although there is some level of 'moving stuff around' at the moment. The driveway has been dug to allow for an entrance to the basement of the building and sheet piling of the excavation will begin tomorrow with the first piers to be drilled from Monday 15th October.

People also continue to ask about the location on campus. If you can't visit then the next best thing is to look at the Google Earth image posted earlier. As an update, here's the view that resident's will have as they leave the building each morning to walk up the University Mall to classes or to undertake research.

A prime location on campus!


02 October, 2007

Bulk Excavation Begins

The bulk excavation of the site has now commenced. Like most sites there is always a risk of contamination. But the news from continued testing has been good with clean 'virgin' sand uncovered about 1.5 metres down. We were aware that we had a small spot with traces of mercury, but this has been remediated and was simply a 'hot spot' that has been removed. There was a small quantity of asbestos also removed that had been refuse from the packing of joists under the building.

Lipman has also established its more permanent site offices on the Anzac Parade side of the site. They have also re-fenced the site. While there is an RDO across the construction industry today (and hence no work) progress has been good. The photos tell part of the story.