Contract LT33 Hofjagdstrasse - the central section of the Lainzer Tunnel / Baulos LT33 Hofjagdstraße - der Mittelabschnitt des Lainzer Tunnels

The 3,500 m long section is part of the new railway line and was tunnelled in accordance with the New Austrian Tunnelling Method. There are five emergency exits in the section. Four emergency exits lead along a branch tunnel and a shaft into the open air and the one in the Lainzer Zoo leads directly to the open air as an adit. The two-track running tunnel and the crosscuts were driven from the shaft in Hofjagdstrasse next to the B1. Only absolutely essential works for the construction of the emergency exit shafts were carried out on the surface. The tunnel drive was through flysch rocks consisting of seasonal layers of marl, limestone and claystone and was excavated by hydraulic excavator loosened by blasting. In the sections under built-up areas, great emphasis was placed on the continuous monitoring of rock mass deformation and surface settlements. The continuous monitoring of vibration measurements and noise emissions caused by tunnelling was also of great importance and determined the sequence of work underground. After completion of the tunnelling work, the concrete works were carried out using two mobile steel formwork units. The internal works to the emergency shafts were carried out in parallel, so that the contract section can be handed over for the subsequent equipment and track works from the middle of 2010.