Description
The twin-tube cut and cover tunnel is part of the construction work for the highway between Catania and Siracusa. With an approximate length of 800 m, both tunnels are 30.5 m wide, with a maximum height of 9.5 m from the foundation to the keystone and an internal diameter of 13.5 m. The construction of the two galleries was carried out simultaneously in the open air with standard MK Structures.
ULMA solution
The MK system used in this project consisted of a formwork carrier trolley moving inside the tunnel. This was the way to cast complete section. The trolley moves on a rail beam thanks to a rolling system and covers 12.5 m tunnel length. The working pace was high as the panels used to cast the vault were provided pre-assembled.
After pouring one of the segments, the trolley was moved to the next position by means of a hydraulic system. Once in the desired location, the trolley was lifted by means of hydraulic jacks until reaching the required exact level, being then fixed in its position with the adjustable jacks.
The versatility of this product was proven, since using the same structure, and only performing minor adjustments, it was possible to cast the entrance opening of another gallery.
The inner formwork was equipped with a hydraulic system that enabled its movement, both vertical and horizontally. The higher performance reached in this way resulted in lower execution costs. Additionally, the formwork was equipped with an external pneumatic vibration system that gave the concrete a high quality finish and reduced pouring time.
The flexibility of the MK avoided the use of wooden parts for creating the necessary curved shapes. The work at any height as well as the access to all the structures were safe and fast thanks to the working platforms with their respective ladders.
