Geosynthetics April/May 2022 - 37

reducing the number of trucks on the road
required for delivery, saving more than $3
million versus the next cheapest alternative,
and reducing time related to ramp
construction on the project schedule.
The MSE walls with UL-FGA backfill
on this project are flyover ramp retaining
walls FO-1 and FO-2 and Ramp B retaining
wall B-1 and B-2 (AECOM 2018).
The section of the flyover ramp requiring
UL-FGA fill is 450 feet (137 m) long,
and the maximum height of UL-FGA fill
in FO-1 and FO-2 is 40 feet (12 m). The
depth of undercut of the existing soils to
maintain a net zero load on the utility
varies due to the differing height of the
flyover ramp, but the maximum is 6.2 feet
(1.9 m). At 330 feet (101 m) long and 26
feet (8 m) high, maximum, the UL-FGA
fill in Ramp B is shorter in length and
height than the flyover ramps. The depth
of the undercut of the existing soils to
maintain a net zero load also varied for
Ramp B but maxed out at 4.2 feet (1.3 m).
A cross section of the flyover ramp is
shown in Figure 4. The MSE wall system
used with this project for both the flyover
ramp and Ramp B consisted of 4 foot
(1.2 m) tall precast concrete U-shaped
panels with alternating layers of geogrid
and polymer geostrap reinforcements
extending between the retaining wall
faces. UL-FGA installation occurred July
through December 2019 for the flyover
ramp construction (Figures 5a, 5b and
6) and October through December 2021
for the Ramp B construction (Figure 1
on pages 32-33).
Conclusion
This article discusses the conformance
of UL-FGA with the requirements for
MSE backfill per the LRFD Bridge
Construction Specifications (AASHTO
2017). Considerations when using
UL-FGA as MSE backfill are presented,
including potential adjustments to
UL-FGA layout to increase internal and
external stability of the wall. There have
been numerous projects where UL-FGA
has been used as MSE backfill; this article
includes the details of a highway project
in the U.S. where UL-FGA has been used.
References
AASHTO. (2017). LRFD bridge construction specifications,
4th ed. American Association of State and Highway
Transportation Officials, Washington, D.C.
AECOM. (2018). " Retaining wall package 1_004_plans
& profiles, Reconstruction of Route 6 & Route 10
interchange, Providence, Rhode Island. " AECOM, Dallas,
Texas. Aug. 31.
Loux, T. A., and Filshill, A. (2021). " Ultra-lightweight
foamed glass aggregate as MSE wall backfill: Properties
and case studies. " Proc., Geosynthetics Virtual Conference
2021, Industrial Fabrics Association International,
Roseville, Minn., 570-82.
Loux, T. A., Swan, R. H., Yuan, Z., and Filshill, A. F.
(2019). " Pullout testing of geogrids, geostraps and
steel strips embedded in foamed glass aggregate, "
Proc., Geosynthetics Conference 2019, Industrial Fabrics
Association International, Roseville, Minn., 728-37.
McGuire, M. P., Loux, T. A., and VandenBerge, D. R.
(2021). " Field-scale tests to evaluate foamed glass
aggregate compaction. " Proc., International Foundations
Conference and Equipment Expo (IFCEE), American
Society of Civil Engineers, Reston, Va., 157-68.
NCMA. (2010). Design manual for segmental retaining
walls, 3rd ed. National Concrete Masonry Association,
Herndon, Va.
NHI. (2009). Design and construction of mechanically
stabilized earth walls and reinforced soil slopes, vol. 1.,
FHWA-NHI-10-024, Federal Highway Administration,
National Highway Institute, Washington, D.C. G
5b
FIGURES 5a and 5b UL-FGA placement
(a) at the RIDOT Route 6/10 Interchange
reconstruction project. Geogrid reinforcement
can be seen in (b).
5a
FIGURE 6 UL-FGA MSE backfill in the flyover ramp at the Route 6/10 Interchange reconstruction
project. Abutment height shown is one-half of the final height.
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