As with Summer and Winter Olympic Games before them, the Olympic Games of 2016 in Rio de Janiero, Brazil, will rely on new underground infrastructure to make them a success. As the world gears up for the start of the premier global event this weekend (5 August 2016), it is underground infrastructure that will play a major role in their success.

Route of the 16km long new Rio de Janeiro Metro Line 4

Of vital importance is the new 16km long Metro Line 4 underground link that extends the city’s existing two-line metro system from a connection in the famous Ipanema district in the east to the Olympic Park and Olympic Village sites in the Barra da Tijuca suburbs west of the Pedra Branca mountains (Fig 1).

The new line, with its six new stations, is expected to transport more than 300,000 people per day on journeys of 34 minutes between Barra and the city centre; and remove thousands of vehicles each hour from the city’s busy peak-hour streets.

Brazil tunnelling connections

Brazil has an extensive tunnelling history and is an active member of the international tunnelling industry and of its underground space association. The current President of the International Tunnelling and Underground Space Association (ITA) is Tarcisio Celestino of Brazil and a previous President, Andre Assis, was also from Brazil. In 2014, Brazil hosted the 40th ITA General Assembly and the World Tunnel Congress of international tunnelling professionals in Iguassu Falls on the Parana River between Brazil, Paraguay and Argentina.

ITA President Celestino

Speaking of the underground contribution to the 2016 Olympic Games, ITA President Celestino said: “It is rewarding to realize that underground works have contributed so much for the Rio 2016 Olympics: for mobility as well as for urban upgrading. Metro Line 4 was crucial for access of the public to the Olympic facilities. Tunnelling through pure sand below the sea level along Ipanema beach brought technical challenges. Brazilian and German engineers worked side by side to come up with the development of a hybrid solution to push even further the applicability of EPB machines. The development is significant and it is now classified as a finalist for the 2016 series of the ITA Awards.

"The Porto Maravilha is a remarkable project for upgrading the Rio de Janeiro downtown area facing Guanabara Bay and Pão de Açúcar. The area was detrimentally affected in the 1970s following construction of an elevated highway along the shoreline, blocking the famous view. An ambitious project for upgrading the area included a fabulous new museum designed by the Spanish architect Santiago Calatrava and tunnels to replace the elevated highway.

Porto Maravilha waterfront project before (left) and after

"A new model for the real estate market was created, attracting investment which would not have existed had it not been for the tunnels. One of the best examples of Why Go Underground? which the ITA has been advocating since its formation in 1974.

"Another underground solution in preparation for the global attention that will be focused during the Olympics on Brazil and Rio de Janeiro, was duplication of the Joá and Pepino highway tunnels. These traffic facilities were constructed in the 1960s and contributed significantly to the expansion of the city. Their duplication will relieve traffic congestion and improve the quality of life in the southern part of the city considerably. The tunnels are finished with a sprayed concrete final lining, which is a cost effective and environmentally friendly solution promoted by the ITA Working Group 12 and now used extensively in Brazil.

"Rio is forever transformed with all the new tunnels and underground spaces created!"

References

• Preparing for WTC Brazil – TunnelTalk, January 2014
• WTC 2014 video report – TunnelCast, May 2014

Vice President of Brazil Michel Temer, Rio de Janeiro state governor Luiz Fernando Pezão and Rio Mayor Eduardo Paes attended the opening ceremony for the new metro line on 30 July 2016, will only be used by athletes and spectators until September 17, when it will then open to the general public. The 16 km route linking General Osório in the east with Jardim Oceânico in the west runs underground except for a section near the western terminus, where it crosses a cable-stayed bridge over the Lagoa da Tijuca.

Official opening of the new metro line on 30 July

Construction of the project, which runs underground except for a section near the western terminus, where it crosses a cable-stayed bridge over the Lagoa da Tijuca, started in 2010 and was divided into two sections, with an11.46m diameter Herrenknecht EPBM used to excavate the 5.7km long coastal section beneath the water table and through sand, silt, clay and rock ground conditions; with drill+blast taking the remaining 5km of twin tube tunnels west through the mountains and beneath the Tijuca Forest Park.

The drill+blast work of Lot 11 between the new Jardirn Oceanicol and Gavea cut-and-cover stations in Barra, progressed through the gneiss rock of the mountains and under a maximum overburden of 840m. The contract was completed by the joint venture led by Oueiroz Galvao with partner companies Odebrecht Infraestrutura, Carioca Engenharia, Cowan and Servix.

The EPB machine for the 5.7km coastal alignment between Gavea and the junction with General Osorio Station and beneath the dense urban areas of Ipanema and Leblon, was the first use of a TBM in Rio de Janeiro. The bored tunnel contract of Lot 21 was completed by a joint venture led by Odebrecht Infraestrutura with partner companies Carioca Engenharia and Oueiroz Galvao.

The TBM was launched from a site outside General Osorio Station, at the easternmost end of the project, where the new line links to the two other metro lines and advanced at depths of 12-18m below the water table, which lies about 3-4m beneath the surface. Excavation through complex mixed ground of rock and wet running sand did cause a sinkhole under a street in the Ipanema district and while there was subsidence of buildings above, there were no injuries or collapse of structures.

The 22,000 concrete segments for the 10.33m single-tube, double-track running tunnel were cast in moulds supplied by Herrenknecht Formwork. The steam curing carousel system of the casting facility was equipped with five full sets of segment moulds for the seven segments plus key in each ring. A combination of steel cage and macro-synthetic fibre reinforcement reduced the amount of steel in the lining and the polyfibres will prevent explosive spalling of the concrete in the event of an in-tunnel fire.

Highway tunnel connections

The TBM progressed at an average rate of of 10 rings/day and reached a best of 19 rings in one 24hr period, which is the equivalent to about 35m of tunnel excavated in one day.

Twin-tube Grota Funda highway portals

Another tunnelling project completed to assist transportation needs around the city ahead of the Olympic Games was excavation of the 1.1km twin-tube Grota Funda highway tunnel on the 25km three-lane highway Transit Transoueste project between Barra and Santa Cruz in the city’s southern suburbs. The twin tube tunnel was completed by contractor Odebrecht and replaces a narrow 5km section of the existing Avenida das Americas, which wound its way around a small 250m high peak. Two lanes of the highway are for normal traffic with the third lane reserved for buses.

The 100m² cross-section of each 14m wide x 8m high tunnel was excavated using drill+blast through Pedro Branca solid rock that includes intrusions of volcanic diabase dikes. Sandvik drill jumbos were used for drilling the typically 165 charge holes in each face. Excavation followed a 13-hour cycle comprising 4 hours drilling (including bolt holes), 2.5 hours charging, 4 hours mucking out, 1.5 hours shotcreting and 1 hour surveying, allowing for three blasts a day in the twin tunnels.