The project Semmering Basistunnel (SBTN), which is
about 27.3 km, consists of a twin tube single-lane tunnel between the Gloggnitz and Mürzzuschlag portals including cross connections and emergency stations. The entire tunnel is initiated through the site portal Gloggnitz as well as three intermediate accesses designated as ZA Göstritz, ZA Fröschnitzgraben and ZA Grautschenhof.
The project is divided into three construction lots:
• Lot SBT1.1 - Tunnel Gloggnitz
• Lot SBT2.1 - Tunnel Fröschnitzgraben
• Lot SBT3.1 - Tunnel Grautschenhof

In the lot SBT3.1, the tunnel advance works for both tunnel stretches are carried out through the two shafts Sommerau 1 and Sommerau 2 commencing from the shaft bottom area. The main construction units are:

• 2 x 100 m shafts with diameter of 8 and 14 m
• 2 x 7 km long (70 - 94 m²) single-track rail tunnel
• 14 cross connections separated 500 m at most

The geological characterization of the project presents
28 rock types. These extend from loose rocks to solid
rock types with weak zones. The rock types of the con-
struction lot SBT 3.1 Tunnel Grautschenhof are composed of different rock types of the Semmering’s Crystalline and the permomesozoic units of the Central Alpine. Schist and phyllite are described as the significant units of the Semmering’s Crystalline with an occurrence of approx. 45%. In the disturbance areas 20% gneiss and 10-15% limestone are to be expected.

Underground excavation, rock support and grouting work

• Shaft excavation method: pre-shaft (concrete piling

with excavator), D&B sinking

• Shaft dimensions: 8 m and 14 m respectively, 100 m

deep each

• Shaft bottom caverns: 2 injection caverns of 30 m

each (180 to 210 m²)

• Underground logistics: shaft hoisting system and vertical conveying system
• Tunnel excavation method: conventional methods

(top heading and benching)

• Excavation length and cross section: 6.9 and 7 km

respectively, 70 to 94 m²

• Grouting works and exploration drilling
• Standard rock support: shotcrete (276’000 m³) and

systematic rock bolts (164’000 pcs)

• Additional rock support: spilling bolts (343’000 pcs),

lattice girders (210’000 m), LSC elements (4’300 pcs)
and pipe umbrella (146 m)

• Cross connections: 14 units around 36 m long (36 to 40 m²)

Underground water and frost protection work

• Umbrella seal and perimeter waterproofing systems

incl. cross connections: 310’000 m³
Surface- and groundwork

• Earth, pre-cut and geotechnical works
• Unloading and transfer conveyor system to stockpile
• Roadwork
• Fresh water and drainage system
• Installation of cable pipes and channeling

Concrete work

• Tunnel reinforced concrete lining incl. cross connec- tions
• Construction concrete: 366’000 m³