Geosynthetics February/March 2022 - 26

Geosynthetics for solar farm development
The following case studies explore
solar farm stabilization projects benefiting
from the use of high-strength geosynthetics
to stabilize unsuitable soils.
FIGURE 6 Site at Chicot Solar Energy
Center during construction
distance for import and export of materials
increases, so does the cost and time
associated with this method.
Option (2), chemical stabilization,
PROJECT HIGHLIGHTS
CHICOT SOLAR ENERGY CENTER
OWNER
NextEra
LOCATION
Chicot County, Ark.
CONTRACTOR
Overland Contracting
ENGINEER
Black & Veatch
GEOSYNTHETICS PRODUCT
Mirafi RS380i geotextile
GEOSYNTHETICS MANUFACTURER
TenCate Geosynthetics Americas
26
Geosynthetics | February March 2022
improves short-term strength, bearing
capacity and shrink/swell behavior; however,
durability issues are a top concern,
and there are potential health hazards.
These methods are time and weather
dependent, and the resulting structure
experiences a breakdown very soon after
hardening. For certain soil types (i.e., sulfates
present with lime stabilization), reactions
between naturally occurring ground
elements and the chemical additives are
detrimental to the durability of the stabilized
platform. Additionally, chemical
stabilization requires a unique mix of
design and cure time, and still the results
are highly variable.
Option (3), geosynthetic reinforcement,
enhances the performance of the section,
which allows the contractor to use less
aggregate. This approach also reduces, or
eliminates, planned undercutting. No special
equipment is required to place and
install geosynthetics. There is no cure time,
and following compaction, the geosynthetic-stabilized
roadway can be immediately
trafficked. The geosynthetic material
becomes a permanent structural component
of the system.
Case study: Chicot Solar Energy
Center, Chicot County, Ark.
Located in southeastern Arkansas, the
Chicot Solar Energy Center was, at the
time of construction, the largest utilityscale
solar project in the state (Segrave
2019). With 350,000 solar panels planned
for the 825-acre (334-ha) site, the facility
was capable of generating enough power
for more than 18,000 homes.
This site was constructed over former
rice fields, presenting significant soilsupport
challenges for site access and
development. Cultivating rice requires
sufficient water supply to maintain constant
flood conditions. The wet 2019-20
construction season added to the history
of heavy agricultural irrigation
and resulted in highly saturated soils,
which drove the need for site stabilization.
The subgrade soils were classified
as CH soils (fat clay) under the Unified
Soil Classification System. The soil has a
soaked CBR of 1.5%. Moisture-induced
volume changes and strength loss due to
high water content were of concern for
load support. Figure 6 shows site conditions
prior to stabilization measures.
Once it was determined that stabilization
efforts were required, the Giroud-Han
unpaved design methodology (Giroud
and Han 2004) was utilized to determine
the required unreinforced and reinforced
thickness of aggregate. The Giroud-Han
method employs stress-distribution theory
to estimate vertical pressure on the subgrade
resulting from a wheel load at the
road surface. The aggregate base thickness
required, h, to reduce the vertical pressure
imparted on the subgrade to a value equal
to its estimated bearing capacity is computed
using Equation 1.
Geosynthetics February/March 2022

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