Twin track railway tunnel, length 5.21 km (3.23 miles), full section of 140 m² approx. Excavation method: NATM, top heading, bench and invert.
Geology description
Lower shell limestone, higher bunter sandstone: clay and sandstone layers, high groundwater inflows of 400 l/s at the interface between the limestone and sandstone encountered.
Two Lane Highway Tunnel Length: 7,047 ft (2,1km); Height: ~35 ft x ~29 ft; Section: ~840 ft2 (78.4m2) Excavation included 4 vehicular cross passages connecting existing east tunnel. Constructed using two headings from North (drill-blast) and South (mined-excavator); Grouted pipe arch for pre-support and rock anchors where needed.
Geology description
Difficult tunneling conditions as result of the presence of the Lavantal fault, un-favorable bedding and severe jointing of gneiss and mica schists.
Preliminary tunnel improvement study including alignment and tunnel design
Commencement - Services
February 28, 1998
Completion - Services
December 30, 1998
Location
Allegheny, PA
United States
Technical data
Preliminary alignment study looking at four new tunnel options and rehabilitation of the existing tunnels. Design of two to four lane highway tunnels up to 6100 ft (1860 m) in length supported with rockbolts, reinforced shotcrete and lattice griders.
Geology description
Interbedded Shales and Sandstones with Limestone interbeds, Coal and Claystones. Decomposed to highly weathered fractured rock at the tunnel portals.
