LOCATION: THE ORIENTE TUNNEL PROJECT, COLOMBIA
Client Issue
Medellin, is nestled in the Aburra valley among the Andes mountain range. Access into and out of Medillin has been a formidable challenge ever since the Spanish explorers first arrived in the 1540’s.
Medellin has transformed into the second largest metropolitan in Colombia. The city continues to expand and grow economically at 7% GDP and with this, the issue is development of the infrastructure, specifically road tunnels to enable sustained growth of the region. Tunnel Oriente is just one of these projects
The Job / The Challenge
The Oriente Tunnel project on completion will alleviate the ever increasing road traffic in the region and lessen the transit time from the airport to the city. 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 being 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 also highly sensitive in view of the social impact on the environment due to the potential reduction in the water table level through the various sub surface 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.
The Solution
The solution was the first ever supply of microfine cement into Colombia for tunnel pre-excavation grouting! This came about through numerous meetings between the client and Normet to discuss the project taking into consideration the tunnelling construction design (drill and blast), grouting materials and methodology needed to meet the clients 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 also 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 TP pumps.
Without exception, 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. This has been achieved not purely through the use of the TamCrete MFC and the methodology, but also through diligent execution of the grouting by the Contractor and his grouting team. As on many occasions, it is collective and not simply down to one piece of the puzzle!
Altogether, 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. To date, 8,791 m of tunnel has been excavated, approximately half the tunnel length and Normet continues to supply and support the Contractor on the grouting process.