A 1.25-mile section of a CSX rail line near Milstead, Alabama was experiencing excessive ballast settlement and required frequent track maintenance due to poor subgrade soil conditions. CSX considered three alternatives to rehabilitate the track: relocating the line, stabilizing the subgrade with geotextile, or reinforcing the ballast with geotextiles and geogrids. CSX chose the ballast reinforcement solution using Tensar BX1300 geogrids, which involved raising the track, installing geogrid and geotextile, and replacing the ballast. This solution allowed CSX to restore normal train operations at a lower cost than relocating the line.

1. CASESTUDY
BALLAST REINFORCEMENT S47
Condition of rail line prior to rehabilitation.
CSX RAIL LINE REHABILITATION
MILSTEAD, ALABAMA
Application: CSX Transportation relied on the
Spectra®
Rail System to reinforce a 1.25-mile-long
section of a Class 1 rail line located near
Milstead, Alabama.
The Challenge: Poor soil conditions at the site
were causing excessive ballast settlement and soil
pumping. CSX was required to maintain, realign
and surface the track every two to four weeks.
Even with this regular maintenance, the track was
subject to a five mile per hour speed restriction.
Site Conditions: The rail line runs parallel to the
Tallapoosa River at an elevation above the high-
water mark. The alignment is situated in a wide,
deep, cut-through interbedded with sand and
weak clay layers about 25 feet below the original
phreatic surface. The cut has 2:1 side slopes with
benches at vertical intervals of approximately
25 feet.
Erosion of the cut slopes and benches filled
the section’s drainage ditches. Lack of drainage
saturated the subgrade soils and reduced
its shear strength. Heavy rail traffic caused
excessive settlement, pumping of fines through
the ballast and progressive failure of the railway
embankment and shoulders.
Alternative Solution: CSX considered three
design alternatives to restore the track to
normal operation: (1) relocating the alignment
of the track at great expense, (2) stabilizing the
subgrade using a geotextile installed over the
existing subballast, or (3) reinforcing the ballast
using a combination of geotextiles and Tensar®
Biaxial (BX) Geogrids.
The Solution: CSX selected the ballast
reinforcement solution with Tensar BX1300
Geogrids as the best option for improving the
corridor and mitigating maintenance costs.
Research demonstrated that a ballast section
reinforced with geogrids was able to carry up
to 10 times the amount of rail traffic as an
unreinforced section of equal thickness.
PROJECT HIGHLIGHTS
Project:
CSX Rail Line Rehabilitation
Location:
Milstead, Alabama
Installation:
December 1983
Product/System:
BX1300 Geogrid, Spectra Rail System
Owners:
CSX Transportation
Design Engineer:
Newby Soils, Inc.
Materials Supplier:
Tensar International Corporation
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2. CASESTUDY
SPECTRA_CS_RCSX_5.07
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BALLAST REINFORCEMENT
The Spectra Rail System design called for raising
the track, then undercutting and removing the
existing ballast. A filter fabric was installed over
the exposed sub-ballast, followed by a single
layer of Tensar BX1300 Geogrid. Next, the track
was lowered and a minimum of 12 inches of new
ballast was placed using hopper cars. The track
was then raised through the ballast and vibrating
tines compacted the ballast in place.
With the Spectra Rail System, CSX was able to
restore normal operations at a fraction of the
cost of relocating the line. After three months
of operation with no track stability issues,
transportation officials raised the section’s
maximum speed to 35 miles per hour. After four
years of successful performance all speed
restrictions were lifted.
The Spectra Rail System Advantage: CSX
benefited from the Spectra Rail System by
substantially reducing the construction time and
costs associated with renovating the rail line. They
were able to improve subgrade performance and
durability by changing the dynamics of load
interaction with the subgrade and more evenly
distributing load pressure. CSX gained these
advantages while reducing the required ballast
thickness. Overall, the project required less
excavation and allowed an installation approach
that was simpler, faster and more economical
than the conventional solution.
Additional Information and Services:
Tensar International Corporation, the leader in
geosynthetic soil reinforcement, offers systems for
improving structures such as roadways, railroads,
construction platforms and parking lots. Our
products and technologies, backed by the most
thorough quality assurance practices, are at the
forefront of the industry. Highly adaptable, cost-
effective and installation-friendly, they provide
exceptional, long-term performance under the
most demanding conditions. Our support services
include site evaluation, design consulting and site
construction assistance.
For innovative solutions to your engineering
challenges, rely on the experience, resources, and
expertise that have set the industry standard for
more than two decades.
Raising the existing track to allow placement of the
geogrid within the ballast section.
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