Zañartu Ingenieros Consultores SpA.

Las Raíces Tunnel

Project Description:

The Las Raíces Tunnel is located in La Araucanía Region on international Route 181-CH, 20 km to the west of the town of Lonquimay. It was built in the 1930s and originally formed part of the railroad network. It is located 1,010 m above sea level, is 4,520 m long, and passes 600 m below the mountaintop, making it the country’s longest road tunnel. The structure itself is 4.2 m wide and lined with precast concrete along its entire length. It provides passage through a fold of the Andes, connecting the Cautín river basin with the Alto Biobío area. In the 1990s, the tunnel was converted to carry road traffic, and a single-lane, one-way carriageway was created.

The purpose of this latest project was to improve the tunnel’s service capacity, including structural repairs to the lining and installation of a waterproof membrane. Groundwater had been seeping in at numerous points, running to either end of the tunnel over the road surface itself. This resulted in icy conditions and the formation of stalactites during the winter months, hindering traffic flow. The roadway was then paved with concrete, and drainage and lighting infrastructure was installed, along with traffic lights to control vehicle flow. The nature of the project meant that work had to be carried out in adverse climatic conditions and at night, and partial suspension of transit was required.

Las obras realizadas consistieron en un mejoramiento de su capacidad de servicio, que contempló reparaciones estructurales en la bóveda e impermeabilización de ella mediante membranas. En efecto, existían numerosas vía de ingreso de aguas subterráneas que evacuaban hacia los portales por sobre la superficie de circulación, y en época invernal se producía el congelamiento y formación de estalactitas que interrumpían el tránsito. En segundo término, se procedió a la pavimentación de la calzada con hormigón, drenaje y saneamiento, iluminación y control de tránsito mediante semáforos. La ejecución de las obras obligó a la realización de faenas en condiciones climáticas adversas, suspensión parcial del tránsito usuario, y faenas en horario nocturno.

Gallery: Las Raíces Tunnel

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