Work has started on a tunnelled solution to the traffic congestion in Guayaquil, the principle commercial city in Ecuador, South America.
The two three-lane tunnels will direct commuter traffic from the city centre to the northern suburbs through the hills that divide the city.
A JV between OHL of Spain and local construction company Semaica won the US$60M contract, including the M&E installations, as the lowest of five bidders. Work on the 28-month long contract started in May 2000 after adjustments following ‘dollerization’ in January 2000, when Ecuador officially adopted the US dollar as its national currency in place of the sucre.
Excavation of the two tunnels will advance from four portals and the finished thoroughfare is due to open to traffic in September 2002.
The two 140m² tunnels are 264m and 585m long with lengths of cut and cover at each portal for a total of 541m and 745m, respectively. The mined sections pass through heavily weathered intrusive rock known locally as Lutita and ranging from Type V at the portals to a central core of Type III-II on the Beniawski rock classification system. The friable weathered material has little cohesion, and although dry in the dry season, is susceptible to excessive water percolation during the heavy rains of Ecuador’s three-month wet season from January to March.
“We will use two ITC-Shaeff machines to excavate the tunnels as a topheading, bench and invert sequence,” said Mauricio Martinez, a director and contracts manager of JV partner Semaica. “A second new machine has been purchased to work with a machine we already owned. Topheading excavation in the poorest rock types will be proceeded by umbrellas of protective spiling using 12m long spiles and a 3m overlap. We will also install long fibreglass nails.” Support of the rock types in Types V and IV comprises heavy steel arches on about 75cm centres and layers of steel-fibre reinforced shotcrete to a total of some 18cm. Rockbolts and shotcrete will support the central core of better quality rock in which drill and blast may also be required for excavation. Once excavated, the tunnel tubes will be finished with a waterproof membrane system and a 80cm thick reinforced in-situ concrete lining.
