Mt Ovit Tunnel, Turkey
The twin tube Mt Ovit Tunnel is one of Turkeys most significant pieces of civil infrastructure. The highway tunnel measures 14,700m and upon completion will be the worlds 6th longest road tunnel and Turkeys longest. More than just being a truly massive tunnel, the societal and economic significance of this project is also great. By linking the Black Sea with Turkeys eastern regions and the rest of the Middle East this tunnel will turn the Black Sea Port into a major trade hub. Using the current highway the journey between Mardin and the Black Sea takes 10-11 hours and is inaccessible during the winter, once the Mt Ovit Tunnel is completed the journey will take 3-4 hours and will be accessible all year round
Initially, this project faced major safety concerns and time delays caused by the installation of steel mesh. Given the potential delays caused by the extremities of winter conditions on Mt Ovit it was crucial to the project owners that there be minimal to no delays in excavation speeds. “The use of steel mesh reinforcement in the shotcrete lining (of the Mt Ovit Tunnel)… presented safety issues and relatively slowed application.” (P. Guner, 2014).
To solve these problems designers looked to Macro Synthetic Fibers as a possible alternative. Given that macro synthetic fiber reinforcement is batched directly into the concrete mix there is no need to fix any reinforcement to the tunnel wall. This results in significant time savings.
Once the Mt Ovit Tunnels designers decided to make the switch to BarChip Macro Synthetic Fibers excavation speeds increased from 7.10m/day to 9m/day and overall production speeds increased 25%. This speed increase led to the project being completed an estimated 106 days earlier than expected which represents a huge saving in costs for the project owner and minimised the impact of a harsh Mt Ovit winter.
Furthermore, the shift to BarChip fibers led to a far safer work environment for the tunnels work crew as it removed the need for workers to operate under dangerous, unreinforced ground.
This blog post draws from the paper “An Overview of the Construction of Turkeys Longest Road Tunnel Focusing on Ground Support Using Macro Fibers as Shotcrete Reinforcement” which was presented at the World Tunnelling Congress 2014.
The paper goes into far greater detail regarding specific tunnel designs and testing results.