MSE wall versatility provides ramp for pedestrian bridge in Virginia

August 02, 2019
MSE walls for Virginia pedestrian bridge

The Huckleberry Trail near Virginia Tech carries commuters and recreational users between Blacksburg and Christiansburg, Virginia. In recent years the trail has undergone expansion to increase the length and add to the area’s network of trails. Coinciding with roadway improvements in Christiansburg, a new bridge was required to cross Peppers Ferry Road to extend the trail deeper into the town. The new arch bridge, dedicated in 2015, is named after Renva Weeks Knowles, a longtime resident of Christiansburg, who donated over $1 million to be used for improvements to the trail. A plaque is fixed to the ornamental bridge abutment design.

Engineered by Gay and Neel Inc., the pedestrian bridge needed a narrow curved ramp on the north end to bring the trail to the elevation of the bridge deck.

The approach ramp was constructed using a back-to-back mechanically stabilized earth (MSE) retaining wall, sloping from grade to a height of roughly 20 ft. The width of the ramp varies between about 16 ft and 30 ft. The use of the MSE wall system supplied by The Reinforced Earth Company allowed for fast construction compared to a conventional cast-in-place retaining wall.

In a back-to-back MSE wall design, the soil reinforcements extend from both wall faces and overlap a distance of at least 30% of the height of the wall.

The overlap of soil reinforcements reduces the amount of lateral earth pressure within the volume of fill, further economizing the design of the internal stability of the MSE walls and allowing for a reduction in material and construction time.

The wall accommodates a tight radius of under 28 ft near the bridge abutment, with the use of a series of truncated-width facing panels. The 10-ft facing panel width used for most of the wall was shortened to about 3 ft for a portion of the wall near the bridge abutment, to accommodate a smaller radius in the horizontal alignment.

Precast coping was anchored to the top course of the MSE wall panels, providing stability to the pedestrian railing running along the top of the wall.

Overall, the MSE wall provided an ideal solution for the bridge’s north abutment, based on factors such as foundation type, cost, and aesthetics to match the architectural appeal of the new bridge.

Mechanically stabilized earth walls Reinforced Earth

Related Articles

The state of Georgia has had its fair share of major highway projects over the last few years, and it is not about to slow down any time soon. Back…
August 01, 2019
Heavily skewed bridges can be a real pain to design and build. Once a bridge’s skew angle creeps over 45°, the challenges of analyzing, designing,…
August 01, 2019
When Patricia Roebling began working as the then-assistant city engineer in Port St. Lucie, Florida, in 1995, a third crossing over the north fork of…
August 01, 2019
I-90 project enclosed pedestrian overpass bridge
A significant feature of the I-90 project is a $6 million enclosed pedestrian overpass bridge and accompanying entry buildings integrated within the interchange. This steel truss bridge with glass curtain walls spans the tollway and connects express bus stations on both sides of I-90, improving mobility and safety for pedestrians and transit users.
Multimodal connectivity is becoming an increasingly popular concept in addressing congestion and quality-of-life issues. While there are abundant…
August 01, 2019
expand_less