Brazilian port tunnel sets new standards Jan 2012
Sandvik News Release
- A 20.5m wide tunnel in Brazil will become one of the widest of its type globally when it is completed later this year.
- Two Sandvik jumbo drill rigs, including a recently delivered two-boom electro hydraulic DT280SC, are operating side by side on each of the project's two faces, which feature a finished cross-section of 211m2.
- The US$2.2 billion Porto Sudeste project, 80km south west of Rio de Janeiro, features at its heart a 1.7km tunnel that will accommodate four iron ore conveyor lines and a 4m wide road. This will allow mining company MMX, whose logistics arm LLX owns the new 52-acre port site, to double its current 50 million tonne annual capacity for shipping iron ore from the newly constructed port.
- The ARG/Civil Port JV has appointed Brazilian specialist tunnel contractor J.Dantas to complete the excavation using the drill+blast method. The tunnel will allow conveyors with a total length of 13km a direct passage through a hillside that separates the new port from a 2.5 million tonne capacity storage facility further inland.
- Once the 20.5m x 11m tunnel and a newly built pier are completed deep-water ships can be loaded at a rate of 12,000 tonne/hr.
- Operating with two twin-boom jumbos on each face, the four booms are drilling 176 holes in the 118m2 top bench, which is scheduled for completion in August 2012. The lower bench is scheduled for completion three months later.
Porto Sudeste tunnel features a 211m2 finished cross section
- Project manager Antonio Vitor de Souza Sobrinho says the contractor is experiencing difficult rock conditions, including decomposed and cracked granite.
- He said: "At best it is Class 2 and 3, and requires extensive shotcreting and rockbolting.
- Generally for Class 2 the shotcrete thickness is 7.5cm, increasing to 15cm for Class 3, 20cm for Class 4, and where we pass through Class 5, 30cm thickness is used."
- Rockbolting is also used extensively using resin type bolts to a 4.5m depth and spaced depending on the granite conditions.
- Sobrinho said: "Despite problems with the rock conditions, we are currently running ahead of schedule. We had anticipated falling behind on a section of Class 5 granite at the Port portal (exit) which was originally estimated to be 20m long but was actually a 52m stretch; all requiring the installation of steel arches."
- He added: "Work at the other portal (header) however is going really well."
- For the 'port' face, the Sandvik jumbo drill rigs are drilling 45mm diameter holes to a depth of 4m, whilst at the 'stockpile' face longer 4.3m holes are being drilled. Sandvik 45mm RT300 button bits with a 6mm front flushing hole are being used, with the contractor regrinding bits on-site every five 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 1.5 hours – and 3 hours rod drilling compared with 1 hour.
- For the first 32m 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.
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