- Pennsylvania Department of Transportation, District 11-0
- Pittsburgh, Pennsylvania
- Our Role
- Soils/Geologic Studies, Foundations, Geotechnical Investigations, Transportation, Highways.
- Small diameter micro-piles stabilized structures without demolition/reconstruction
- Grouted and spin rock bolts secured existing structures and rock blocks
- Pre-cast concrete for the cantilevered roadway slabs expedited construction.
Boulevard of the Allies, a major artery linking the central business district of downtown Pittsburgh to Oakland, Pennsylvania, and the eastern suburbs, is perched on the crest of Duquesne Bluff, a 115-foot high rock slope above the Parkway East elevation.
The presence of Duquesne University, Mercy Hospital, and established businesses adjacent to the inbound westward lanes of the Boulevard forced the designers to extend the four-lane roadway to the slope crest and, at places, cantilever beyond.
Because of the nearly vertical nature of the rock slope adjacent to S.R. 0885, conventional survey would have been impractical, if at all possible. A state-of-the-art concept of oblique aerial digital imagery was used to aid in the design of rockfall treatments. The slope was photographed with a Precision Aerial Survey System Bell 47 Helicopter and a Zeiss RMK TOP15 precision aerial camera. These images were used by Gannett Fleming CADD operators to develop an Intergraph MicroStation topographic file that was used to generate cross sections at any location along the slope. Additionally, a digital photogrammetric mosaic showing existing slope and structural features, as well as proposed treatments was developed. These images were provided in the bid documents and were used by the contractor during bidding and construction.
- Oblique aerial photography used for geologic mapping
- Provided geologic mapping and rock joint studies, including Markland analyses
- Rock slope stability evaluations
- Implemented rock bolting, rock netting, tied back walls, and buttressing
- Geophysical study determined concrete wall and retaining wall thickness
- Foundation design used pin piles
- Post-tensioned rock-bolt design to stabilize the underlying rock slope.