Geosynthetics October/November 2019 - 56

FINAL INSPECTION

The engineered geotextile in
place. Photograph courtesy
TenCate Geosynthetics Americas

Stabilization and reinforcement
of wind farm access roads

T

PROJECT HIGHLIGHTS
WIND FARM ACCESS ROADS
GENERAL CONTRACTOR

Wanzek
DESIGN ENGINEERS

Barr Engineering
INSTALLER

Phillips and Jordan
GEOSYNTHETICS PRODUCT

Mirafi
GEOSYNTHETICS
MANUFACTURER

TenCate Geosynthetics
Americas

56

Geosynthetics | October November 2019

his project is the construction of the first commercial-scale wind farm in North Carolina. It was
for a renewable power generation facility providing clean energy. Constructing the wind farm
required subgrade stabilization and reinforcement for more than 60 miles (97 km) of access roads
that needed to be built in order to erect 104 turbines in the first phase of the Desert Wind Project.
As the only source of entry, the access roads had to support construction traffic over soft, wet
North Carolina farmland soil. The access roads would be used by aggregate and concrete trucks,
by delivery tractor trailers (with heavy turbine components), and for moving cranes between the
wind turbines. The original design specified geogrid with dense-graded aggregate (DGA). The
subsurface investigation revealed that the in situ soils consisted of peat and organic clays with a
California Bearing Ratio (CBR) value as low as 0.7% and silty/clayey sands with a CBR value of
less than 4.0%. From the start of the project, the grading contractor had trouble with the roadways
being too saturated. Multiple attempts at stabilizing the subgrade with geogrid were unsuccessful.
The only way to stabilize the roads was to add additional stone. However, the aggregate imported
by railcars was very expensive. The contractor tried cement stabilization as an alternative; however, this method required too much cement and an excessively long curing time. This option was
immediately ruled out for both time and cost reasons.
Designs with an engineered geotextile were recommended after evaluating the subgrade soils
along with the anticipated truck and crane loadings. An engineered geotextile having a high flow
rate, good filtration and confinement was deemed necessary due to the extremely saturated conditions of the low CBR soils. A geotextile having a high strength at a low strain was recommended
for the worst conditions to help minimize the aggregate necessary for stabilizing the roads. After
a successful roadway test section of 900 linear feet (274 m), the engineering team chose to minimize construction delays and optimize overall costs through the integration of the separation,
reinforcement, filtration and confinement functions into a single product along with the aggregate. G



Geosynthetics October/November 2019

Table of Contents for the Digital Edition of Geosynthetics October/November 2019

Geosynthetics October/November 2019 - Cover1
Geosynthetics October/November 2019 - Cover2
Geosynthetics October/November 2019 - 1
Geosynthetics October/November 2019 - 2
Geosynthetics October/November 2019 - 3
Geosynthetics October/November 2019 - 4
Geosynthetics October/November 2019 - 5
Geosynthetics October/November 2019 - 6
Geosynthetics October/November 2019 - 7
Geosynthetics October/November 2019 - 8
Geosynthetics October/November 2019 - 9
Geosynthetics October/November 2019 - 10
Geosynthetics October/November 2019 - 11
Geosynthetics October/November 2019 - 12
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Geosynthetics October/November 2019 - 14
Geosynthetics October/November 2019 - 15
Geosynthetics October/November 2019 - 16
Geosynthetics October/November 2019 - 17
Geosynthetics October/November 2019 - 18
Geosynthetics October/November 2019 - 19
Geosynthetics October/November 2019 - 20
Geosynthetics October/November 2019 - 21
Geosynthetics October/November 2019 - 22
Geosynthetics October/November 2019 - 23
Geosynthetics October/November 2019 - 24
Geosynthetics October/November 2019 - 25
Geosynthetics October/November 2019 - 26
Geosynthetics October/November 2019 - 27
Geosynthetics October/November 2019 - 28
Geosynthetics October/November 2019 - 29
Geosynthetics October/November 2019 - 30
Geosynthetics October/November 2019 - 31
Geosynthetics October/November 2019 - 32
Geosynthetics October/November 2019 - 33
Geosynthetics October/November 2019 - 34
Geosynthetics October/November 2019 - 35
Geosynthetics October/November 2019 - 36
Geosynthetics October/November 2019 - 37
Geosynthetics October/November 2019 - 38
Geosynthetics October/November 2019 - 39
Geosynthetics October/November 2019 - 40
Geosynthetics October/November 2019 - 41
Geosynthetics October/November 2019 - 42
Geosynthetics October/November 2019 - 43
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Geosynthetics October/November 2019 - 45
Geosynthetics October/November 2019 - 46
Geosynthetics October/November 2019 - 47
Geosynthetics October/November 2019 - 48
Geosynthetics October/November 2019 - 49
Geosynthetics October/November 2019 - 50
Geosynthetics October/November 2019 - 51
Geosynthetics October/November 2019 - 52
Geosynthetics October/November 2019 - 53
Geosynthetics October/November 2019 - 54
Geosynthetics October/November 2019 - 55
Geosynthetics October/November 2019 - 56
Geosynthetics October/November 2019 - Cover3
Geosynthetics October/November 2019 - Cover4
Geosynthetics October/November 2019 - Blank1
Geosynthetics October/November 2019 - GeoConf20_1
Geosynthetics October/November 2019 - GeoConf20_2
Geosynthetics October/November 2019 - GeoConf20_4
Geosynthetics October/November 2019 - GeoConf20_5
Geosynthetics October/November 2019 - GeoConf20_6
Geosynthetics October/November 2019 - GeoConf20_7
Geosynthetics October/November 2019 - GeoConf20_3
Geosynthetics October/November 2019 - GeoConf20_8
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