28.05.2014 | Last bored pile built: Foundations completed for construction of FAIR facility
Today employees of the construction companies deployed on site set in place the last of the total of 1,350 drilled piles. These steel-armored piles with a length of up to 60 meters and a diameter of 1.20 meters stabilize the subgrade so that the later buildings at the FAIR facility will only settle to a limited degree and that they will, above all, sit evenly. Thanks to the optimization of the drilled pile technology, the company was able to conclude the work more than six months earlier than planned.
The pile-drilling work only took 15 months after the company involved had improved the pile-drilling technique on site at a very early stage. With five modern drilling rigs, among them the world’s largest such special drilling devices, which first saw service at the FAIR construction site, the construction companies were able to produce one drilled pile per rig and day.
In the course of the construction work it was also possible to rely on the geological surveys which had been conducted beforehand. “Geological surveys are always difficult, and especially at the depths at which we are working. We did not experience any surprises,” is how Dr. Florian Hehenberger, construction director at FAIR, praised the work of the surveyors. In addition, it was possible to improve the construction of the drilled piles with the effect that fewer piles than originally planned had to be set in place. As a consequence, this construction phase could be concluded more than six months earlier than planned. “Thus we have reached a milestone in this major construction project,” says a visibly pleased Hehenberger.
Building solidly on sand
The heavy FAIR facility – in part with concrete walls several meters thick –requires solid foundations so that its structural works are able to settle as evenly as possible and in a calculable period of time. So as to be in a position to gage the degree of settlement, geotechnical engineers conducted extensive subgrade studies beforehand. In this respect the 250 soil samples confirmed that the subgrade primarily comprises sand, clay and silt. Such soils are compressible, which means that they change their density under great pressure. The foundation concept implemented for FAIR, which foresees that the drilled piles will have contact with the later foundation plates, lowers the degree of settlement and the settlement differences by as much as 50 per cent. The settlements are essentially expected to come to an end one year after the completion of the construction work.
Heavyweights leaving the construction site
The focus is now on the concluding work for this construction phase: a drilling rig recently left the construction site as an abnormal load. In the coming weeks the final three drilling rigs will be prepared for transport. The earth excavated in the course of the pile-drilling work will also be removed from the site in the near future.
The concrete mixing plant which was specially erected for the pile-drilling work is also being dismantled. As the concrete was mixed on site, the transport was less complex as only the individual parts had to be delivered to the site. Thus it was possible to mix the right amounts of concrete as needed at any given point in time. The mixing plant will also be deployed elsewhere on the site.
Shell construction next on the agenda
FAIR is to begin with the shell construction next year. By then various smaller tasks on the construction site will also have been completed. Container offices for the construction supervisors and a container with a visitor center, for example, are being established on the building zone at the northern site access point (Prinzenschneise). In addition, construction site installations have to be completed and a section of access road on the site has to be extended.