Little Switzerland Tunnel
Location
Blue Ridge Parkway, North Carolina
Client
HDR Engineering, Inc.
FHWA - Eastern Federal Lands Highway Division
Services Provided
Tunnel Inspection
Damage Survey
Tunnel Rehabilitation Design
Detailed Drawings and Specifications
Project Overview
The Little Switzerland Tunnel is a two-lane highway tunnel on the Blue Ridge Parkway in North Carolina. The tunnel is roughly semicircular in shape with a height of 20 feet, a width of 30 feet, and a length of 600 feet. The tunnel was constructed in the 1950s in metamorphic rock, and for most of the length is unlined, supported only by rock bolts and chain link mesh. One section, about 100-ft long, required initial support by means of steel ribs, and has an 18-inch thick concrete liner for permanent support. Water seepage through the concrete lining created maintenance problems for the tunnel in winter.
LACHEL FELICE & Associates, Inc. (LF&A), as subconsultant to HDR Engineering, Inc., conducted an inspection and damage survey of the tunnel, including mapping all cracks and deterioration using the full perimeter mapping method and conducting a visual survey inside and outside the tunnel. Overall, the tunnel was found to be in relatively good condition. However, the concrete-lined section had experienced significant cracking in one location, and the cracks, as well as two construction joints, were the source of troublesome water inflows. The water, in conjunction with freeze-thaw action, had resulted in some concrete damage and caused major icing problems in the winter, sometimes forcing closure of a section of the Parkway.
LF&A also developed rehabilitation recommendations for repair of the tunnel. A system of drainage chases was designed for the cracks and construction joints, to intercept water inflow and convey it to the drain at the tunnel invert. LF&A produced detailed drawings and assisted in preparation of the specifications for the rehabilitation work.
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