Mobile formwork is used to cast the secondary lining of tunnels. These large steel structures have profiles tailored to customer requirements and advance along the tunnel alignment from one casting block to the next using travel mechanisms and hydraulics. Larger units can weigh more than 120 tones. At first glance, this equipment may appear to be a more expensive alternative to modular formwork systems. However, when tunnel length and the required finish quality are taken into account, steel formwork carriages offer a sound solution. OSTROJ also manufactures reinforcement carriages for installing steel reinforcement. The equipment is designed to suit specific site conditions, from tunnel dimensions to longitudinal gradient. The design parameters are similar to those for a formwork carriage, and the two units often operate in tandem, one behind the other. “Every project has different requirements, and customers are increasingly considering how to use the equipment once the project is completed. That is why, in addition to manufacturing bespoke equipment, we also offer rental and modification for subsequent projects. We see considerable potential for further cooperation in precisely this flexibility,” says Marek Kušnír, Head of Sales and Marketing at OSTROJ.

From the Prague metro to motorway tunnels

During the construction of the Pankrác–Olbrachtova section of Prague Metro Line D, OSTROJ worked with HOCHTIEF CZ, STRABAG and SUBTERRA. It supplied formwork for running tunnels, station tunnels and an access adit. For the escalator tunnel, it also developed a special 58-tonne unit capable of operating at an inclination of up to 30 degrees. “The greatest challenge was ensuring the safe movement of the entire structure on a 30-degree incline and securing it reliably in its working position. We also have the equipment ready for deployment in the next phase of Prague metro construction,” adds Zdeněk Slavík, Sales Manager at OSTROJ.

Another major contract was the Homole tunnel on the D35 motorway. For MARTI, OSTROJ manufactured a 125-tonne formwork carriage capable of casting 12.5-metre-long sections. For this project, OSTROJ rented out the formwork carriage and sold a reinforcement carriage. The reinforcement carriage was designed with a subsequent project in mind, allowing the customer to reuse it at the Dolní Radechová tunnel with only minor modifications and achieve substantial cost savings.

Mining expertise applied internationally

In developing its tunnelling equipment, OSTROJ draws on nearly 80 years of experience in mining engineering. This expertise was also applied to a contract for the E18 cut-and-cover tunnel near Oslo, Norway, where the company supplied formwork weighing 250 tones, measuring 20 meters in width and comprising 70,000 parts. The equipment incorporated 88 hydraulic supports derived from mining props.

OSTROJ is currently in talks over new contracts for metro, motorway and railway tunnel construction in the Czech Republic and Slovakia, with projects envisaged for 2027 and 2028. In addition to equipment sales, it offers short- and long-term rental, equipment buyback and modifications for subsequent projects. It also provides on-site assembly and servicing.