Asbestos isolation

摘要

The Cesana tunnel, located close to the Italian-French border in Piedmont (North West Italy), is the main structure on the SS24 road improvement works that were planned for the XX Winter Olympic Games. The tunnel has a length of 1860m and is located between a 370m long artificial tunnel and the 1280m long Claviere tunnel along a mountainous road which leads to the picturesque resort. Construction by the Italian-Spanish consortium SIS (SACYR S.A., INC General Contractor S.p.A. and SIPAL) started in March 2005.rnDue to the presence of asbestos-bearing rocks that were unexpectedly discovered during tunnelling, work was suspended at the two excavation fronts in autumn 2006, leaving a 105m stretch of tunnel unexcavated. When the asbestos-bearing rock masses were encountered, the tunnel had been excavated from four fronts simultaneously; two starting from the portals and two from the 290m long access adit (figure 1). In order to isolate the asbestos-bearing rock masses from the remaining parts of the tunnel, two confinement barriers were constructed out of HDPE membrane and fixed onto a frame made out of steel tubes and wooden planks. Access to the face has been provided through two decontaminating filters installed on these barriers.