Line 4 of the Rio de Janeiro Metro; a challenging project

Works require a high degree of engineering know how, advanced technology in equipment, complex planning and logistics to take the rails of the city’s metro to the borough of Barra da Tijuca by the end of 2015

The main structure of the Tunnel Boring Machine (TBM) - popularly known in Brazil as the ‘Tatuzão’ or ‘Mighty Armadillo’ - has already landed and is undergoing pre-assembly. The EPB Shield S-769, manufactured by Herrenknecht, is the largest equipment of its kind ever brought to Brazil. Measuring 11.46 meters in diameter, equivalent to a four-story building, with 120 meters in length and weighing 2,000 tons, the machine will play a fundamental role in the execution of one of the largest and most complex projects of commuter transportation and urban mobility ever developed in the country : Line 4 of the Rio de Janeiro subway or “Metrô”. Running along about 16 km, the line will connect the borough of Ipanema, in the South Zone of the city, to Barra da Tijuca, in the West Zone.

With this equipment, it will be possible to build 5.7 km of underground tunnels in the heart of the South Zone of Rio; one of the most densely populated, and where some of the most highly-valued real estate in the region is located without, however, resorting to detonation or digging of trenches on the surface along the city’s streets and avenues, thus minimizing the impact of the works on the life of the population.

The TBM will also enable the execution of the work four times faster than by conventional methods of construction, which will make it possible to complete all of Line 4 by December 2015 so that the phases of commissioning and assisted operation can be initiated. Thus, the project, whose construction began in June 2010, is expected to begin commercial operation in March 2016, in time for the Summer Olympic Games to be held in Rio de Janeiro.

Due to its grandeur and complexity, the project for expansion of the Rio de Janeiro ‘Metro’ system is one of the themes of the thematic halls of Construction Expo 2013 which will be held by Sobratema – the Brazilian Association of Technology for Construction and Mining from June 5th to 8th, 2013 in the city of São Paulo (see article in this issue).

New dynamics in transportation

Planned to restructure the system of transportation in the South and West zones of Rio de Janeiro, transforming the dynamics of the movement of the city’s population, Line 4 of the Metro is expected to carry approximately 300,000 people per day, removing from the streets no fewer than 2,000 vehicles per hour. The total project cost is R$ 8.5 billion (US$ 4.25 billion).

There will be six new stations: ‘Nossa Senhora da Paz’ in Ipanema; ‘Jardim de Alah’ and ‘Antero de Quental’ in Leblon; Gávea; ‘São Conrado’ and ‘Jardim Oceânico’ in Barra da Tijuca

Studies of demand conducted by the Fundação Getúlio Vargas (FGV) indicate that, in the first year of operation, 91,000 new users will enter the metro system via the Jardim Oceânico station which will provide integration with the existing bus system that serves the region of Barra and Recreio dos Bandeirantes. Another 61,000 people will access the system via the São Conrado station; 19,000 via Gávea; 35,000 via Antero de Quental; 20,000 via the Jardim de Alah stations and 47,000 via Nossa Senhora da Paz.

Through the General Osório station, which is part of the existing Line 1, and which will be the point of connection with the new Line 4, 30,000 users presently pass per day.

With the ultimate completion of the new segment, it will be possible to go from the ‘Barra’ to the center of the city in 35 minutes. Today, such travel at peak hours of the day can take up to two hours on account of the city’s frequent traffic jams.

The construction of Line 4 of the Rio Metro is being executed by the ‘Concessionária Rio Barra’ which consists of two consortiums: One is the ‘Consórcio Construtor Rio Barra’, which is building the West segment between the Jardim Oceânico and Gávea – with approximately 12 km in length. The consortium consists of the Queiroz Galvão company (the leading member), Odebrecht Infrastructure, Carioca Engenharia, Cowan and Servix. The second consortium was established to execute Line 4 South and is responsible for the work between Ipanema and Gávea, in the South zone of the city. This consortium consists of Odebrecht Infrastructure (leader), Carioca Engenharia and Queiroz Galvão. The construction of this segment will involve the use of the TBM.

On the stretch between Ipanema and Gávea, there are 980 direct workers presently employed. Another 2,000, approximately, are actively at work on the line’s West segment, between Jardim Oceânico and Gávea, and that number is expected to reach about 3,000 at the peak of construction in January 2014.

Works on several fronts

Currently, the construction of Line 4 is advancing on several fronts simultaneously, with different construction methods being adopted and absolutely on schedule according to the project’s building consortiums. In the West segment, the main physical progress reported is the completion of the excavation of over 4.2 km of tunnels in rock, between Barra da Tijuca and São Conrado.

Another 5 km of tunnels are being excavated in rock at this time across the Pedra da Gávea. The blasting plan has set a schedule of three detonations per day: one on theBarra da Tijuca work front in the direction of São Conrado;  another on São Conrado, work front in the opposite direction, towards Barra da Tijuca, to meet the first section mid-way; and a third in São Conrado in the direction of the city’s South zone. Each of these fronts consumes an average of 700 kg to 1 ton of explosive per blast which ensures an average advancement of 4.5 meters per day per work front, depending on the quality of the rock. The more stable the rock, the faster the process since containment measures are unnecessary. On the Barra da Tijuca front, where excavations are more advanced, with over 3 km measured from the point of entry, you can carry out up to three detonations per day.

Today, all the sections advancing are being built as “bi-tunnels” (bi-directional track tunnels) ?? . Two separate rail lines will serve for the circulation of the trains, one outbound and one inbound.

In the median strip of Avenida Armando Lombardi, in the borough of Barra da Tijuca, actions were focused on the construction of the Jardim Oceânico station whose diaphragm walls, consisting of 519 panels, have been completed. At the site, excavations began on the body of the station using the cut-and-cover method and the casting of the central pillars is being performed.

According to engineer Marcelo Riolo, production coordinator, the execution of the work required the drawdown of the water table – previously found at about 1.60 meters below the surface to 23 meters in depth. Due to the high salinity of the water at the site, a decision was made to line the station with a special waterproofing fabric.

As regards the São Conrado station, excavations are 100% completed and the construction of the three accesses to the station has begun. The goal of the construction consortium is to start building the structure of the station, boarding platforms and mezzanine by 2014. This station is the closest to the Rocinha hillside community where some 70,000 people live according to the last official census. To serve this community, the state government of Rio de Janeiro plans to build, at the site, a cable car linking the top of the hill to the future station.

But is the 5.7 km where the tracks will cross the South zone that the greatest difficulty for implementation of the project lies. According to Marcos Vidigal, Contract Director at Odebrecht, the defined route of the line is the result of a long period of study and analysis of different possible paths. “In the study phase for this segment, we wound up generating as many as 3,000 documents among which were feasibility studies, geotechnical investigation, geological surveys, testing of water loss, etc.. We studied as many as 33 guidelines for the route until we reached the ideal path.”

Parallel to these investigations and analyzes, the Fundação Getúlio Vargas performed feasibility studies to establish the ideal locations for the stations. “The foundation did the studies and issued a report assuring that the best solution for the Rio de Janeiro Metro network would be to implement its expansion, Line 4 in this route, and determied where the stations should be located.”

All one needs to do is to look at a map to realize that the stations are equidistant from each other. Each has an area of influence. The idea is to make each station attract demand within a radius of 500 meters.

In defining the locations of the stations, what also carried weight was the assessment of the volume of vehicles traveling in the vicinity. “We commissioned an evaluation of the timing of the traffic lights on the surface to assess the disruptions that interruptions in traffic would cause at that location during the execution of the works. This study gave us inputs to establish the best ways to detour the traffic.”

So much planning is already providing positive results for, just like in the South segment, work is proceeding on schedule. In Gávea, such work is focused on soil probing. In January, the installation of a construction site began on the campus of the ‘Pontifícia Universidade Católica’ (Catholic University) of Rio de Janeiro (PUC-Rio), with completion scheduled for April when the excavation of route’s tunnels will begin. A service tunnel will also be built at the site to be used for ventilation and as an emergency exit. The construction of the station begins in the second half of this year. The station will have two levels, with the possibility of future expansion. At the top level, the Gávea-Leblon, tunnel will be excavated by the TBM, and on the lower level, the São Conrado-Gávea bi-tunnel will be excavated using the same method as in São Conrado and in Barra da Tijuca.

In Leblon, the removal of the pavements of ‘Praça Antero de Quental’ and ‘Avenida Ataulfo de Paiva’ (where traffic has already been interrupted in two of its segments: between ‘Rua General Venâncio Flores’ and ‘Avenida Bartolomeu Mitre’, and between ‘Avenida Borges de Medeiros’ and ‘Avendia Afrânio de Melo Franco’) has been completed. At the moment, prospecting work is being carried out to map networks of interference underground (water, electricity and telephone connections, among others).

Main challenges

According to the engineer Lucio Silvestre Chruczeski, Contract Manager for the Rio Barra Construction Consortium, one of the biggest design challenges in West segment is the blasting of large sections of rock for the excavation of the tunnels. “It is a work of a high degree of complexity that requires an infinite amount of care considering the region where the detonations are carried out. Today we have approximately 4,000 meters of tunnels excavated and about 950 meters of train stations and parking lots, excavated in rock, on both fronts - São Conrado and Barra da Tijuca. This corresponds to 35% of the tunnel planned in project already executed. The stretch of tunnels in rock, currently in progress, accounts for over 5 km, between Jardim Oceânico and São Conrado. In this stretch, work is proceeding on two fronts simultaneously, in opposite directions. These two tunnels will meet in February 2014. There are about 1,600 meters to go for them to meet. It is a project that involves a few level of safety, complexity of execution and preventions because it is being performed in an urban area, with about 4000 vehicles passing daily,” explains Chruczeski.

He tells us that the precautions involve safety concerns in the levels of blasting, traffic signaling, and communication with the community surrounding the work site, among others. “We are careful to advise residents and people circulating in the area what time the detonations will be performed. With that done, we have to cordon off the passages to the area so that the detonations are carried out within safety levels. Furthermore, we also monitor vibration levels and the radius of the vibration so that they don’t cause damage to existing buildings. Today, the level of vibration is 4.2 millimeters per second, which does not affect the surrounding buildings. What is actually perceived is a slight displacement of air. And we are taking care not to exceed this level,” explains the engineer.

He also says that 100% of the buildings located in regions close to the detonations are monitored daily, with instrumentation, settling markers, etc.

As a further complication, Chruczeski cites the diversity of the types of buildings found in the area. “They range from very large residences to small dwellings that do not always have an approved blur print, which demands greater care.”

The logistics also has its complexities. To start the work, the consortium had to install work sites with large equipment in the middle of streets with intense traffic. Just to give you an idea, by the end of March over 100,000 truck trips had already been made for the transportation of excavated material removed from the tunnels.

All that demands a lot of planning and a high level of accuracy when the time comes to perform these works.”

What is also seen as major challenge is the wide variety of soil types found in the route of the new line, which means different types of treatment and the adoption of various construction methods. The greatest difficulty was found precisely in the stretch between the sea and the ‘Lagoa da Tijuca’ (a lagoon) where there is soft soil of low resistance.

Soil surveys that preceded the works revealed the existence of at least one meter of land fill placed on the surface at the time of the construction of the road surface. Below this land fill there is a layer of clay which varies along the longitudinal profile of ‘Avenida Armando Lombardi’, and finally, as a basic geological formation of the region, a large layer of sand. To overcome this challenge, since the beginning of construction, the consortium engaged a high level of technology using, for example, polymers that, along with hydraulic diaphragm machines, enabled the stabilization of the sandy soil for the construction of the diaphragm walls.

For the drawdown of the water table, found at a low depth, Chruczeski recalls that 107 pumps which operated non-stop were used..

Breaking a few eggs

There’s an old adage that says you can’t make an omelet without breaking a few eggs. Likewise, it is almost impossible to build a subway line without causing some level of inconvenience to the public, no matter how much care you take to try to minimize it. In the case of Line 4 of the Rio de Janeiro Metro, the largest number of “broken eggs” was concentrated at the existing station at ‘Praça General Osório’ in Ipanema, where the rails of the new line will meet Line 1. To perform the work that will promote the integration of the lines, the station which serves about 30,000 people daily was closed on February 23rd and should remain out of service for about 10 months.

The reason for the problem is that the station was not designed for an expansion of the system. There was a lack of long-term planning. To ensure the connection between the two lines it will be necessary to build a tunnel linking the ‘Cantagalo’ and ‘General Osório’ stations, which is impossible to do while maintaining the circulation of the trains.

The Cantagalo station was also put out of service but only for 15 days as of the same date, and it has already gone back to normal operation. Today, the station plays the role of Line 1 Terminal Station in the South zone

To serve users and minimize the impact of closing the General Osório station, the MetrôRio concessionaire which operates the system created a special operation for the period of construction, offering buses linking Cantagalo to General Osório. Currently, 23 vehicles circulate at intervals of three minutes performing this service.

Ecological footprint

Respect for the environment is a point of honor in the process of building Line 4 of Rio’s Metro which is observed by the two consortiums operating on several fronts. This concern became clearly evident, for example, during the drilling of the tunnel for the line through the massif of the ‘Focinho do Cavalo’ which is part of the Tijuca Massif. At this point, the rock cut with daily detonations using a blasting plan that was carefully planned to ensure the least impact on the environment and inconvenience to the population.

Before the explosions, the Rio Barra Construction Consortium determined the removal of over 2,700 specimens of the native flora, especially orchids and bromeliads that were found on the hillside. Among the specimens found there were even rare examples of the Cattleya lobata orchid.

The plants were removed with the help of mobile lifts and nine practitioners of rappelling and mountaineering and transported to the Botanical Garden Institute for Research of Rio de Janeiro, which gave support and technical advice for the operation. The consortium signed an agreement with the Botanical Garden for accommodation of the rescued species in the science institution’s bromeliad collection. These species were acclimated and will later be used in the reclamation of degraded areas of the ‘Parque da Tijuca’ upon conclusion of the works.

The same concern is present in the installation of work sites and in the start of construction of the ‘Nossa Senhora da Paz’ station in Ipanema, and the ‘Antero de Quental’ station in Leblon. The design of Nossa Senhora da Paz was modified to reduce environmental impacts and to interfere as little as possible in the routine of borough’s residents. The new format and size of the underground station enabled a reduction of 860 m2 of excavation area (15% less) and the conservation of the lake inside the square. It also enabled the preservation of the greatest possible number of trees. Of the 292 trees that existed at the site, 215 (equivalent to 74%) will remain untouched. Among them, the oldest one in the square - a century-old fig tree with 12 meters in height and a 22 meter canopy. In places where the removal of trees was inevitable, the consortium opted to transplant them to safe areas, observing even the original position of each tree in relation to the sun until they could be returned to the square at the end of the works.

But some of the trees that could not survive removal had to be cut. In such cases, the commitment of the consortium is to replant new seedlings of the same species when the works are completed as a form of environmental redress.

Other 400 seedlings will be planted to meet the requirements of the ‘Instituto Estadual de Ambiente’ (INEA - State Institute of the Environment), and another 182 seedlings will be planted to comply with the ordinance of the ‘Secretaria Municipal de Meio Ambiente’ (SMAC – Municipal Department of the Environment), totaling 582 specimens.

At the work fronts in Barra da Tijuca and Sao Conrado, water treatment plants were installed for the reuse of all the water resulting from the excavation of tunnels and stations. Since 2011, over 65 million liters of water have been reused. Stations for recycling of various materials were also installed. All debris and residues generated in the works undergoes screening, is packaged in a hydraulic press and put up for sale to licensed recycling companies. Since March 2011, 24,510 kilograms of paper / cardboard and 2,388 kg of plastic were sold. All the money raised is invested in awareness campaigns, training in the areas of quality, safety, environment and health for employees.

These temporary benefits will add to the positive impacts, of a permanent nature, resulting from the reduction of air pollution, the reduction in the time required for the population’s daily commutes in the city and the withdrawal from circulation of 2,000 vehicles per hour from the streets that connect Barra da Tijuca, the South zone and the center of the city.

Equipment

To meet the needs of the construction of Line 4, some R$ 180 million (US$ 90 million) are being invested in the purchase of equipment, among which the TBM. According to Marcos Vidigal, it is a volume of investment similar to what is usually done for the construction of a large hydropower plant.

“Among the purchases that have already been made, besides the ‘Tatuzão’ (TBM), I would underscore nine gantry cranes, three concrete plants, several concrete mixer trucks, Munck® winch trucks and a robot for shotcrete. Not to mention all the peripherals such as compressed air units, etc.. Part of this material is manufactured in Brazil, part of it is imported,” says the engineer.

He explains that the option to purchase the fleet instead of leasing it from rental companies is due to the need for immediate availability of equipment and for fear of a lack of supply in a very heated market like today’s. “Our process is continuous. The fact that we have our own concrete plant at the work site, dedicated exclusively to the project, gives us assurance that our volume needs, which are very large, will be met," he says.

To ensure the maintenance of all the fleet, an exclusive maintenance and repair shop will also be established.