11 Jan 2012
Record breaking tunnel will open up access for iron ore to new port in Brazil
The Porto Sudeste tunnel project in Brazil features a 20.5 m wide tunnel and is designed to house four conveyor lines to become one of the widest tunnels of its type globally; with two Sandvik jumbo drill rigs operating side by side on each of the projects two faces along its 1.7 km length.
Four Sandvik jumbo drill rigs are being used by Brazilian tunnelling contractor throughout excavation of a record breaking 20.5 m wide tunnel; designed to house four conveyor lines to convey iron ore to dockside ship loaders in a new port.
The project, the Porto Sudeste, is located in Sepetiba Bay, close to Itaguai City some 80 km south west of Rio de Janeiro City.
The new port is owned by LLX Logistica SA and will allow the company to double its capacity for shipping iron ore to 100 Mt/year.
This increased capacity will allow MMX (Mineração Metálicos SA) – and also owned by Eike Baptista – to increase production of its Serra Azul ore mines in Minas Gerais. The port will occupy a 52 acre area and includes a storage capacity of 2.5 MT. Water depths will also be increased to 21 m together with construction of offshore berths to handle large ocean going vessels such as Cape size and VSCC.
The new terminal will be used primarily to export iron ore mined by MMX. It is located some 100 km north of the company’s existing terminal at Campos.
20.5 m wide tunnel
A 1.7 km x 20.5 m wide x 11 m high tunnel is being excavated to provide access to the port from two storage stockpiles with a complete belt circuit for the ore.
The total length of the belt circuit will be approximately 13,000 m and with a capacity of 12,000 t/h, will feature four conveyor lines – two x 1600 mm and two 1800 mm – and a 4 m wide road.
Main contractor for the project, the ARG – Civil Port jv, appointed Brazilian tunnelling specialist J. Dantas to undertake excavation of the 1700 m tunnel using drill and blast techniques.
Featuring a finished total cross-section area of 211 m2, J.Dantas has opted to prepare a 118 m2 top bench – scheduled for completion by August 2011; followed three months later with completion of the lower bench.
Throughout drilling J.Dantas is relying on a fleet of four Sandvik jumbos, including a recently delivered DT820.
Operating with two twin boom jumbos on each face, the four booms are drilling 176 holes in the top bench, using 14 ft drill rods at one face and 16 ft drill rods at the second face.The contractor is experiencing some difficult rock conditions with, according to Project Manager, Eng. Antonio Vitor de Souza Sobrinho, very decomposed and cracked granite.
“At best it is Class 2 and 3 and requires extensive shotcreting and rockbolting,” he said, elaborating, “Generally for Class 2, the shotcrete thickness is 7.5 cm, increasing to 15 cm for Class 3, 20 cm for Class 4 and where we pass through Class 5, 30 cm is applied.”
Rockbolting is also used extensively using resin type bolts to a 4.5 m depth and spaced depending on the granite conditions. With Class 2, for example, a 2.0 m x 2.23 m pattern is drilled, reducing to 1.5 m x 1.7 m for Class 3 and 1.3 m x 1.3 m for Class 4.
“Despite problems with the rock conditions, we are currently running ahead of schedule, thanks in part to the performance of the Sandvik jumbos and drill tools,” said Eng. Antonio Vitor. “We had anticipated in falling behind on a section of Class 5 granite at the Port portal (exit) which was originally estimated to be 20 m long but was actually a 52 m stretch; all requiring the installation of steel arches.”
“Work at the other portal (header) however is going really well,” he confirmed.
For the ‘port’ face, the Sandvik jumbo drill rigs are drilling 45 mm diameter holes to a length of 4 m whilst at the ‘stockpile’ face longer 4.30 m holes are being drilled.
Throughout drilling J. Dantas is using 45mm dia Sandvik RT300 ( type 7766-5245A-S48) Button bits.
The Sandvik RT300 button bits feature a 6 mm front flushing hole and have a 45 mm
diameter to provide high penetration rates, straighter lines, longer bit life and reduced energy consumption. The system has a single grade of cemented carbide , designated XT48, and a universal face design.
To ensure an increased drill metre life cycle the contractor is regrinding the bits on-site every 5 holes.
“By undertaking 12 grindings we are achieving 240 drilled metres with each drill bit,” said Maintenance Foreman, Ivander dos Santos.
Production Engineer, Ricardo Pereira confirmed that the company is achieving a 12 hour cycle at the header portal and a 24 hour cycle at the exit portal, with the additional time being allocated mainly to shotcreting – up to 8 hours compared with 1½ hours – and 3 hours rod drilling compared with 1 hour.
For the first 32 m the tunnel’s gradient is level from the header increasing to 0.3% - 2% to allow a naval tunnel to pass below the Porto Sudeste tunnel.
The recently delivered DT820SC is a 2-boom electro hydraulic jumbo for fast and accurate drilling in tunnels and caverns.
It features two HLX5T rock drills to deliver superior performance with a high consumer life.
The TB90 universal booms have large optimum-shaped coverage and full automatic parallelism. The booms can also be used for cross cutting and rock bolt drilling.
A FOPS (ISO3449) safety cabin is fitted and the unit is powered by a 110 kW, 149 hp diesel engine.
“The new DT280SC is a really excellent rig from a maintenance point of view,” said Ivander dos Santos, adding, “It is totally different to other models introducing new technology, machine performance and very high quality drilling. The cabin also offers very good visibility.”