Chilean Tunnelling

Santiago in winter (credit Liebherr Chile)

A few months ago I did a research piece on the tunnelling sector in Chile for Tunnels and Tunnelling International. The sector is extremely buoyant across all major sectors and more is yet to come.

“The market is quite active now, as there are some really interesting projects under development and coming in. There are road projects, metro project, hydroelectrical projects and mining projects,” says José Miguel Galera, managing director of consultant Subterra, which has been designing tunnels in the country for over 20 years and does 50 percent of its business in Chile.

But perhaps the most exciting future project for Chile will be the Paso de Agua Negra road tunnel running between Chile and Argentina and promoted by a joint governmental organisation known as EBITAN. “All tunnellers are positioning ourselves for this really interesting project. They called for prequalification at the end of 2016 and just two months ago it was published that 10 JVs have presented their candidature and 4 are Chinese. The other 6 are from the rest of the world,” says Galera.

The scheme involves construction of twin 14km road tunnels and is intended to improve regional connectivity particularly between Argentina and Chilean ports. Despite the enormous length of the Argentinian and Chilean border the number of crossings is small and largely consists of minor roads. The existing Agua Negra route for example is a minor road used just in summer as it runs along an altitude of 4780m meaning that snowfall blocks the route in winter.

CaptureThe new tunnel will be around 1000m lower and is planned as a twin tube due to its length and height. A second passageway offers many safety advantages and by having two equal tubes natural air circulation is enhanced reducing energy costs. It was also decided that each tunnel as a single lane is much safer from a driver perspective. With two tunnels and one-way direction each, light vehicles might keep a good speed and are not delayed by heavy traffic taking the outer lane.

The two tunnels will be 40m to 50m apart and descend from Argentina into Chile with the Argentinian entrance 4,085m above sea level and the Chilean entrance at 3,620m giving the tunnels a slope of 3.37%. Each of the road lanes will be 7.5m wide with space either side for pedestrians. The internal height of the tunnels will be 4.8m and emergency tunnels for people will connect both main tunnels at 250m spacings along the whole length. Vehicular interconnection galleries will be located every 1,550 m.

The industry is now waiting to hear who the successful prequalifiers will be and whoever ultimately wins this project will undoubtedly take on lessons from other tunnelling projects that have been carried out in the Andes including a raft of hydropower schemes. The most recent of these are the Alto Maipo project and the Los Condores project which both include significant tunnelling works for construction of the headrace tunnels and other infrastructure.

Read the full article in Tunnels and Tunnelling International


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