With almost three kilometers under the Carioca Massif, one of the largest road works in Rio transformed travel between regions separated by the terrain, required extensive rock drilling, and brought together engineering, geology, ventilation, and safety solutions that marked the city’s urban expansion.
The Rebouças Tunnel crosses the Carioca Massif for about 2.8 kilometers and creates a direct link between Rio Comprido, in the North Zone, and Lagoa, in the South Zone of Rio de Janeiro, reducing dependence on routes through the Center.
According to the historical survey published by the Engineering Club, the complex was calculated to reduce a trip between Ipanema and the central region by approximately 30 minutes, while the crossing of the galleries was projected to last about five minutes.
Rebouças Tunnel crosses the Carioca Massif
Formed by two main sections, the passage includes parallel galleries that extend for 2,040 meters between Lagoa and Cosme Velho, plus another 760 meters to Rio Comprido, after a viaduct built between the two sections.
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Although the straight-line distance may not seem extraordinary for a metropolis, the mountainous terrain turned this connection into a road challenge, forcing drivers to bypass more extensive areas and compete for space in increasingly crowded corridors.
By crossing the natural barrier instead of following it on the surface, the tunnel introduced a continuous underground route between the two sides of the massif and altered the design of urban travel in a region marked by geographical limitations.
30-minute savings changed travel in Rio
Calculated before the construction of the Paulo de Frontin Overpass, the 30-minute gain reflected the road configuration available at that time, when the new route already allowed leaving the South Zone towards the central area without repeating the longer path.
Long before the start of drilling, an expressway on that axis already appeared in the Agache Plan, developed in the late 1920s to reorganize and modernize Rio de Janeiro, although execution only occurred decades later.
Construction mobilized engineering and geological studies
Started in 1962 and completed in 1967, the works were under the responsibility of the Superintendence of Urbanization and Planning, Sursan, which established an agreement with the National School of Geology of the former University of Brazil to study the terrain.
Before and during the underground advancement, teams analyzed aerial photographs, rock faults, fissures, joints, and inclinations of the massif, identifying formations predominantly composed of facoidal gneiss and migmatite along the planned route of the complex’s galleries.
In the more complex points, surveys guided the choice of excavation techniques, shoring, and safety procedures, while cooperation between engineers and geologists allowed the work to be adjusted to the conditions found within the mountain.
In areas of compact rock, equipment performed drilling throughout the section planned for the gallery; where reinforcement was required, steel plates filled with concrete replaced wooden structures more prone to deterioration.
Excavations reached 5.6 kilometers in rock
Although it favored circulation and ventilation, the design with separate galleries increased the complexity of the construction, as each lane was seven meters wide and left little lateral space for the movement of teams and equipment.
Adding up both directions and the different sections, the excavations reached approximately 5.6 kilometers in rock, a dimension that highlights the effort required to open a continuous passage under the Carioca Massif in a fully urban area.
Besides the excavation, the structure incorporated systems considered modern for a roadwork of that size, combining clean air intake, smoke removal through chimneys, and emergency and fire-fighting equipment distributed along the route.
Telephones installed every 150 meters allowed for assistance requests within the galleries, reinforcing the operational safety of an underground corridor that needed to function continuously in one of the city’s busiest areas, throughout the entire route.
Work gathered thousands of workers
To sustain the pace of construction, the sites functioned like an industrial complex, with mechanical and electrical workshops, concrete and compressed air plants, accommodations, restaurants, and service areas organized alongside the work fronts.
About 2,000 workers operated in shifts for nearly 24 hours, while the total number of people involved in the project reached 5,000 during the peak period, according to the Engineering Club’s survey.
It was also necessary to set up a dedicated operation to remove the rock, as approximately 400 cubic meters of crushed stones were removed daily from the excavation points and transported by 40 trucks during certain periods.
Part of this material was used for the formation of Flamengo Park, connecting the tunnel opening to another major urban transformation carried out in Rio de Janeiro and increasing the use of waste produced during the excavations.
Tunnel was a reference in urban engineering
Inaugurated in October 1967, after five years of construction, the Rebouças Tunnel was named after the engineers André and Antônio Rebouças and was presented at that time as the largest tunnel in Latin America and the largest in the world in an urban area.
Starting in 1976, the first bus lines began to use the route, expanding the role of the passage, which until then was mainly associated with the advancement of the automobile and the creation of expressways in the city.
Through the Lagoa exits, the flow began to distribute in different directions of the South Zone, while on the Rio Comprido side, the connections reached corridors that lead to other regions and the main road exits of the municipality.
Conservation maintains strategic connection of Rio
Throughout its presence in the road network, the tunnel also required conservation interventions carried out by the municipal administration, including resurfacing of the tracks, recovery of the drainage system, and installation of clear concrete panels on the side walls.
These measures aimed to preserve a passage subjected daily to urban traffic and maintain the operation of a structure that continues to connect regions separated by the terrain between the North Zone and the South Zone of Rio, decades after its opening.
What other work hidden under a Brazilian mountain has changed the route of a major city so much without being noticed by those who cross its galleries daily and rarely know the engineering built around this underground path?
