The second excursion in the course of the foundation engineering and soil mechanics lecture in the summer semester 2022 was a visit to the construction site of the project U2/U5 Linienkreuz - section: Matzleinsdorfer Platz. In addition, a shaft was visited near Pilgramgasse, which is an accompanying measure of the underground construction.

The group was received on site by DI Hornich, DI Özkoral and Ing. Pfeffer. In order to give the students an overview of the construction project, the most important points of the extensive project were presented. Afterwards, the group split into two small groups.

One group made its way to Pilgramgasse. In a shaft in the inner courtyard of a residential building, boreholes are being drilled for heave injections, which will be used to compensate for future subsidence in the course of the underground construction. Mr. Hornich explained in detail how the heave injections work and what challenges are to be expected during the execution.

The other group descended into the approx. 30 m deep excavation pit at Matzleinsdorfer Platz to inspect the ground freezing and the start of tunnel driving. At this point, the formation of the frost body of the ground freezing in the area of the under-tunneling of the Gürtel had already been completed and mining had already begun. However, the working face was not yet far advanced and could thus be viewed from the excavation pit, as could the icing pipes of the brine icing at the beginning of the tunnel. In addition, several 30 m high, exposed diaphragm walls could be seen in the excavation pit, which are rarely seen exposed in such a way.

Afterwards, groups were exchanged so that all participants could get a deeper insight into this extensive construction project.

A big thank you to DI Hornich, DI Özkoral and Ing. Pfeffer, who made it possible for the 4th semester students to visit such an interesting construction site. Further excursions are planned in the future to follow different construction phases of this extensive project.