Geosynthetics February/March 2022 - 20

Reinforcement over soft soils with high-strength geogrids
as a catenary single layer at the interface
between the columns and the soil structure
(Figure 8).
Vertical stresses on the geosynthetic
FIGURE 7 Fill material being placed over the reinforcement layer
would lead to severe differential settlements
in the surface of the structure.
Spacing between piles is therefore crucial
to develop efficient soil arching.
A load transfer platform (LTP) with
geosynthetic reinforcement can be
installed immediately above the columns
to help transfer the load from the soil
structure to the columns. By doing so,
spacing between piles can be significantly
increased and the piles' caps size can be
decreased. In addition, the reinforcement
can be used to counteract the horizontal
thrust of the embankment fill, eliminating
the need for raking piles along the
extremities of the foundation.
Two design models are currently in
FIGURE 8 End of first day of installation at
the Port of Guaymas, Mexico
use in the U.S.: the Beam Method and
the Catenary Method. The Beam Method
(Collin 2004; Collin et al. 2005; Schaefer
et al. 2017) considers multiple layers (at
least three) of low-strength geosynthetic
reinforcement equally spaced within a
select granular structural fill (i.e., LTP) that
act as a single rigid beam. The Catenary
Method (BS8006-1:2010) considers one
single high-strength geosynthetic that acts
20
Geosynthetics | February March 2022
reinforcement and its strain and tension
must be calculated, too. Several models
have been developed to calculate the
vertical stresses and several others to
calculate the strain and required strength
in the geosynthetics. Sloan (2011) summarizes
12 different arching theories to
directly calculate the vertical stress, and
three analysis methods to calculate the
strain and tension in the geosynthetic.
Each column-supported embankment
analysis procedure is categorized based
on preliminary ratings for the appropriate
use of performance criteria/indicators,
subsurface conditions, loading conditions,
material characteristics, construction
techniques and geometry. Given the
extent of the analysis methods available,
their complexity and the scope of this
article, design methods will not be discussed
in detail herein.
Case study: I-95/Telegraph
Road interchange
piled embankment
Each day, close to 50,000 motorists pass
through the Telegraph Road Interchange
in Alexandria, Va., along the integral
I-95/495 Capital Beltway between Virginia
and Maryland. In early 2008, extensive
upgrades to the interchange began as part
of a multiyear project tied to the final
phase of the Woodrow Wilson Bridge
project. Roughly $235 million was dedicated
to the interchange's improvement,
including a grade-separated interchange,
new ramps, bike and pedestrian trails,
321,000 yards (294,000 m) of paving, 11
bridges, drainage improvements, retaining
and noise walls, and environmental
mitigation. The goal of the new interchange
was to improve vehicle capacity
and provide safer and more efficient
Geosynthetics February/March 2022

Table of Contents for the Digital Edition of Geosynthetics February/March 2022
