Hitachi ZX350LC-7 CTA keeps Vienna metro in motion

A Hitachi ZX350LC-7 excavator with a clamshell telescopic arm (CTA) is being utilised on an important infrastructure project in the centre of Vienna. This follows on from successful below-ground excavation projects using similar models in Paris and Barcelona, among others.

Special application machinery

The special application machine can remove soil from below ground level and was selected by the U2 17-21 consortium to work on the expansion of Vienna’s metro. The aim is to extend the U2 line between Matzleinsdorfer Platz and Neubaugasse, which started in February 2021 and is due to be completed in 2028.

The subway is continually expanding in line with the city’s growth. The U2 17-21 consortium, made up of companies Strabag and PORR, won the contract to build four new stations and three emergency exits on the U2 line for around €480 million. Additional work worth about €49 million was added later.

A delicate excavation project

The project involves moving millions of cubic metres of soil from depths of 30 metres, bringing it up to five metres above ground level. The Hitachi ZX350-7 CTA was selected thanks to its precision and quick cycle time, which is estimated to be 45 seconds. This is significantly faster than the cycle time of a rope or crane excavator.

“The achievable depth of 32 metres (including 2 metre local extension) was essential to our decision when selecting the ZX350-7 CTA excavator,” says Project Manager Michael Stoifl. “The 1.5m³ ISO clamshell bucket size was also an important factor. In my opinion, it is a reliable and efficient machine.”

In addition, special measures are required to prevent surface movements during the excavation. The enhanced hydraulics of the ZX350LC-7 CTA, combined with the arm’s high-speed extension and retraction, and the powerful pull-up force results in smooth and efficient operation.

Constructing a sustainable transport solution

The stations are built using a method called The New Austrian Tunnelling Method (NÖT). The tunnels are excavated conventionally, while the inner walls are made of concrete using formwork carriages.

A tunnel boring machine (TBM) is used to connect the stations. The segments for the tunnels are manufactured off-site and transported to the construction site. Only one TBM is used instead of two to save costs, but this requires precise coordination.

An important step to reducing emissions in Vienna

Despite the scale of the project, the metro will have a relatively low environmental impact over its lifespan. Expanding the subway is an important step towards reducing CO2 emissions from Vienna’s transportation network and enhancing mobility for the city’s residents and visitors.