Pörzberg Tunnel - L1048

The current regional highway L 1048 and Future B 90 as a motorway feed for the urban conurbation involving the three towns of Saalfeld, Rudolfstadt and Bad Blankenburg to the A 71 is being upgraded along the entire route and in some cases realigned. The Schaala Bypass represents a component of this scheme. It is intended to remove the considerable ever growing amount of traffic from the town where there are two bottlenecks and traffic lights regulating bidirectional traffic. The solution was found in the shape of a bypass to the north with a two-lane tunnel with a carriageway width of 8.0 m and two emergency pathways each 1.0 m wide. The tunnel which had to be produced by mining means and coming from the east passes through middle coloured sandstone over a distance of roughly 500 m before penetrating lower shell limestone with up to 80 m overburden following a roughly 40 m wide fault zone. The fault zone runs in a valley cleft (Laasetal) including a watercourse between the various rock Formations with very little remaining covering above the tunnel amounting to less than 4 m. The tunnel was produced by mining means applying drill+blast, staggered to form the crown, bench and floor, with lengths of advance varying from 80 cm to 1.60 m. in the fault zone supporting was undertaken with lances and a supporting wedge at the face. The main tunnel was driven by mining means beginning on July 16th, 2007. The breakthrough for the crown heading took place on February 12th, 2008. Although 80 % of the excavation route was forecast to be beneath the groundwater and underground water, there was very little inflow registered: 3 m/s or a maximum of 5 m/s in the Laasetal valley. The tunnel's inner shell consists of a watertight concrete structure without a classical umbrella seal, whereby the bulk was produced with a closed invert. Only a roughly 220 m long sector in limestone, which is located above the groundwater level, was left with an open floor. A C 30/37 concrete with thicknesses of 40 to 60 cm was installed in 10 m long blocks using formwork cars. Contraction joints are set between the blocks with joint strips including a central hose, steel plate and grouting inlet. Expansion joints were only produced at the two portals. The main tunnel was provided with portals at both closures. There are 2.50 m wide recesses forming breakdown bays at both sides. For ventilation in the event of fire a channel was prepared in the upper cross- sect ion by installing an intermediate ceiling, by means of which smoke gases can be removed should an incident occur. Three evacuation tunnels with lengths of 82, 110 and 176 m, which are merely lined with shotcrete, serve self-rescue purposes. The operating technology with extensive equipment is housed in the operations centre east and west. Worth mentioning as far as the operating technology is concerned are the planned firmly installed foam extinguishing unit, the LED lamps for lighting the tunnel as well as the traffic guidance system with changing signs because a major upward gradient links up directly with the western tunnel exit. Within the scope of the town bypass scheme Submissions were invited for the tunnel including the operations building involving private prefinancing. Work began on March 1st, 2007. The project has largely been completed in its carcass state. It is planned to open it at the end of 2009.

Country: Germany
Region: Thuringia
Tunnel utilization: Traffic
Type of utilization: Road Tunnel
Client: Free State of Thuringia, Straßenbauamt Mittelthüringen
Consulting Engineer: Müller+Hereth
Test engineer: Ing.-Büro Prof. Duddeck und Partner GmbH
Contractor: Porr Technobau und Umwelt München
Main construction method: Trenchless
Type of excavation: Drill-and-blast
Lining: Shotcrete/Concrete Formwork
No. of tubes: 1
Tunnel total length: 1,145 m
Cross-section: RQ 10.5T, approx. 90 m²
Contract Volume: 19.2 mill. Euro (roughwork), 1.8 mill. Euro net (operations centre) (without VAT and private prefinancing)
Construction start/end: March 2007 till September 2009
Opening: December 2009