Chilean President Michelle Bachelet Kicks off San Cristobal Tunnel at Groundbreaking CeremonyChilean president Michelle Bachelet, minister of public works Eduardo Bitran, and Karl Traub, general manager of the concession company Túnel San Cristóbal, attended on 26th May, 2006 the groundbreaking ceremony that officially kicked off work on the El Salto-Kennedy urban road bypass. The project will be built and operated by a concession company controlled by Hochtief of Germany and Grupo ACS of Spain. Visit www.hochtief-pppsolutions.de and www.grupoacs.com The road scheme has a length of four kilometres, whereof a 1,830 m-long tunnel and 2,200 metres of roads at grade. It will connect the north and south of Santiago between La Piramide area, in the municipalities of Huechuraba and Recoleta, and the intersection of El Cerro Avenue, Los Conquistadores and Lo Saldes bridge, in Providencia municipality. The twin tunnel crosses San Cristobal Hill and will considerably shorten commute times and improve urban connectivity between the north and south of the Chilean capital. The tunnel will connect together two urban highways previously cut off from one another. The project includes the construction of two parallel tunnels, one per direction and each carrying two lanes. The typical cross section is 70 sq m. The two tunnels will be connected by crosscuts for service and/or rescue. One of these cross passages has the necessary dimensions to allow for vehicular traffic. Their maximum dimensions are 4.3 x 4.45 m. In the surrounding region, several fundamental rock units can be distinguished as well as unconsolidated sedimentary deposits. The fundamental rock units constitute the very hilly zones and the rock base of the region (stratified volcanic and sedimentary rocks of continental origin). The unconsolidated deposits have filled the basin where is situated the city of Santiago (fluvial and fluvioglacial deposits, volcanic ash deposits amongst others). Throughout the alignment, crews expect tuff formations and volcanic breccia (A3), porphyric andesites (A2) and hypoabyssal intrusive rocks (Tp). Tamrock jumbos for drilling and subsequent blasting will be used to dig in the rocky areas. There will be two drives at each tunnel, one from each end with one jumbo working at each heading . Three Tamrock jumbos are available (two three-boom rigs and one two-boom machine). Those with three booms are Axera T11 F-315Cs and the two-boom jumbo is a Paramatic H 205-90. Visit www.tamrock.sandvik.comForepoling for umbrella vaults has been executed using the two-boom jumbo. For looser ground, a Cat 320 and a Cat 330 excavators will be used, sometimes equipped with hydraulic breakers. Visit www.cat.comSeven different support patterns have been envisaged, according to the characteristics of the ground. The peculiarities of these patterns are as follows: Type 1 to 3 - Dywidag anchoring bolts, 3 m in length, and fibre-reinforced shotcrete, 3 cm minimum; Type 4 - identical plus lattice girders every 1.5 m; and Type 5 to 7 - TH 29 steel supports every 100 and 50 cm, with 18 to 33 cm of shotcrete. Visit www.dywidag-systems.comBroyt loaders and 10 cu m tipper trucks will be used for the mucking-out. Visit www.toro.sandvik.comThe San Cristobal tunnel will be equipped with state-of-the-art technology, including sophisticated ventilation systems, back-up energy supply, static and variable signs, modern safety and control systems with the use of closed circuit cameras, rescue vehicles, emergency telephones, alarms and loudspeakers, amongst other equipment. The ventilation, lighting and anti-fire devices are part of the turnkey contract.The cost of the scheme amounts to USD70 million (more than CLP36.9 billion). The tunnels will open during the first half of 2008 and around 1.8 million people living in more than 10 municipalities will benefit from the project. Click cl/25. Visit www.moptt.cl and www.tunelsancristobal.cl 24/06.