Greece’s largest foundation contractor Edrasis was no doubt delighted to win the contract to construct a 25m-deep basement for the new Athens headquarters for National Insurance, Greece’s leading insurance company. Little did it know that it would still be hard at work in the neighbourhood two years later.
The plan was to construct a rotary bored pile retaining wall around the site perimeter and install ground anchors as the 25m-deep rafted-basement area was excavated.
Part way into the project, and Edrasis found itself in discussion with the owner of an adjacent site, the Onassis Foundation, trying to gain permission to install temporary ground anchors below its site.
It soon transpired that Edrasis’ work on the National Insurance plot had awoken the Onassis Foundation to the potential for developing the underground space below its site – which it was planning to turn into a cultural centre.
Athens is famous for its road congestion and lack of parking space, and the ability to provide underground parking within a new development is highly desirable.
As a result Edrasis was invited to tender for the foundation work, complete with a 25m-deep basement, for the Onassis Foundation.
The two sites are separated by a small side road and the two basement walls would be running very nearly parallel about 25m apart. Clearly, it was impracticable for Edrasis to press ahead with conventional ground anchors.
Even if adequate anchor capacity could be achieved in the available space, the anchors from the two excavations would be tensioning the ground in opposing directions and the risk of anchors physically touching was great.