Project Description

Lachel & Associates, Inc. performed an inspection and developed rehabilitation recommendations for a highway tunnel.

The Pinnacle Ridge Tunnel is a two lane highway tunnel on the Blue Ridge Parkway in North Carolina. The tunnel is basically semicircular in shape with a height of 19 feet, a width of 30 feet, and a length of 750 feet. The tunnel was constructed in the 1950's in metamorphic gneisses and schist rock and fully lined with a reinforced concrete lining. Continuous water seepage through the lining near the portals had contributed to cracking and spalling of the lining as well as increased maintenance requirements and problematic winter ice formation, causing closure of a section of the Parkway in some cases.

Scope of Services

Lachel & Associates, Inc., working as subconsultants to HDR Engineering, Inc., performed a visual inspection of the tunnel, as well as a thorough damage survey for the entire tunnel length. Based on the damage observed, Lachel designed and supervised a follow up investigation program consisting of core drilling and probing through the concrete lining into the surrounding rock. The coring indicated that the concrete lining thickness varied significantly along the tunnel and that voids between the lining and the rock were present in some areas. Based on the inspection and coring results, Lachel developed a rehabilitation program to fill existing voids, minimize groundwater inflows, and repair damaged sections of the concrete lining. Lachel provided HDR with specifications and drawing details for completing the rehabilitation work. In addition, Lachel prepared detailed construction cost estimates for implementing the rehabilitation program.

Client

HDR Engineering, Inc.
FHWA - Eastern Federal Lands Highway Division