Barcelona Metro Service Tunnel CollapsesOn 27th January a major collapse occurred on a 233 m-long service tunnel under NATM construction as part of line 5 extension to Spain's Barcelona metro, resulting in a 25 m-diameter, 32 m-deep sinkhole. A sandstone fault had been encountered at the face two days earlier, causing a fall of about 1,000 cu m of ground. Concrete pouring was attempted to arrest the situation, but this was in vain. Water pressure in the fault fractured the tunnel sidewall and triggered the collapse, bringing down a surface building. Some 2,000 cu m of concrete was then poured into the void in an attempt to stabilize the area, but a second hole appeared on 3rd February. It has now been decided to seal off and fill up the service tunnel excavation, a job that will take three weeks and 18,000 cu m of concrete. The three buildings nearest to the two sinkholes will have to be demolished. Construction on Line 5 will carry on using NATM, but the frequency of test drilling along the alignment will be increased to avoid a recurrence. Click es/22. Visit www10.gencat.net/gencat/AppJava/cat/esp/carmel/50201especialcarmel.jsp 07/05. Click to enlarge