Halcrow’s unique GRANIT (GRound ANchorage Integrity Testing) system was used to check the condition of the anchorages of cables supporting a tent covering the Temple of Apollo Epikourios at Bassai, in the Peloponnese.
The temple, built in the 5th century BC owes its good state of preservation to its remoteness, which has spared it the ravages of acid rain and, in an earlier age, avaricious explorers. In 1986 UNESCO declared the temple a World Heritage Site and restoration began.
An immense, white, multi-sectioned tent was erected over the building to protect the work. The tent’s guy ropes – or, more accurately, steel hawsers – were designed for a life of 20 years, yet the painstaking restoration work is nowhere near complete.
The question being asked, then, is whether the protective structure would remain safe while restoration continues. Halcrow was contracted to test all 200 bolt anchorages using GRANIT – the beauty of this system is that it is non-destructive and non-invasive, so testing can be repeated as often as required without affecting the integrity of the anchorage. It works by analysing the frequency response of a bolt when small impacts are applied to the head, from which the bolt’s condition can be determined.
The results of the testing were supplied to the client, the committee responsible to the Hellenic Ministry of Culture for the restoration program, so that an appropriate schedule of maintenance for the cables can be devised.