The Oriente Tunnel Project, Colombia- Rock and Ground Support Optimisation

Significant decrease in water ingress achieved with teamwork and TamCrete MFC Fast Set

Contractor

-

Processes

Rock and Ground Support

Location

Colombia

The Project 

Medellin has transformed into the second-largest metropolitan in Colombia. Nestled in the Aburra Valley among the Andes mountains, the city continues to expand and grow economically at 7% GDP.  

Development of the infrastructure is a crucial issue. Tunnel Oriente is one of many road tunnel projects that make sustained growth of the region possible. The tunnel will alleviate the increasing road traffic in the region and lessen the transit time from the airport to the city. 

The Challenge 

The Oriente Tunnel is twin-bore, with a total length of 8.2 km and a diameter of 11 metres for each bore. The tunnel is constructed through gneiss and granite rock formation, with the tunnel alignment intersecting numerous highly faulted zones, including the main Samarcanda fault, significantly increasing the risk of water ingress into the tunnel during the construction phase.  

The project is highly sensitive in view of the social impact on the environment due to the potential reduction in the water table level through the various subsurface fault zones. As a result of the challenging geology and potential environmental impact, pre-injection grouting (PEG) of the tunnel drive was considered essential in reducing the surrounding hydraulic conductivity of the jointed rock mass to and end requirement, at the time of design, of 10 litres water ingress per minute per 100 metres of tunnel, equating to a permeability coefficient of 10-8. 

Quick Facts

  • 3,246 tons of TamCrete MFC Fast Set supplied
  • Significant decrease in water ingress achieved with teamwork
  • Reduced blast cycle times
  • Support for the client in all stages of construction

The Solution 

The solution was the first-ever supply of microfine cement into Colombia for tunnel pre-excavation grouting. Numerous meetings between the client and Normet discussed the project taking into consideration the tunnelling construction design (drill and blast), grouting materials and methodology needed to meet the client's end requirement. 

TamCrete MFC Fast Set, in conjunction with TamCem additives was chosen as the most appropriate and efficient pre-injection grout system. TamCrete MFC Fast Set has a particle size distribution of d95 <16 μm, which afforded increased grout-ability and early age strength gain, enabling the contractor to meet the allowable water ingress specification and reduce blast cycle times. 

Normet was instrumental in the design of the grouting works, advising the client on grout drill hole depth and configuration, STOP criteria, plant and accessories and grouting methodology. In addition, Normet supplied the full range of mechanical packers and post-grouting TamPur resin and TamPur pumps. 

Project Outcome

The TamCrete MFC injected locations along the tunnel drive has resulted in a significant decrease in water ingress, below the limits set in the contract. Diligent execution of the grouting by the Contractor and their grouting team together with TamCrete MFC and Normet methodology proves that project success is not simply down to one piece of the puzzle. 

Normet continues to supply and support the Contractor on the grouting process. To date, 8,791 m of tunnel has been excavated, approximately half the tunnel length. 3,246 tons of TamCrete MFC Fast Set has been supplied to the Oriente Tunnel along with mechanical injection packers, TamCem and TamPur materials and pumps.  

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