Geosynthetics Overview
CE387C – Geoenvironmental Engineering
Prof. Jorge G. Zornberg
Department of CAEE
The University of Texas at Austin
The World
of Geo‐
Materials
Definition
Geosynthetics: Planar products manufactured from
polymeric material, which are used with soil, rock or
other geotechnical engineering material as an integral
part of a man‐made project, structure, or system (ASTM
D 4439)
Geosynthetics: Synthetic polymeric materials that are
specifically manufactured to be used in geotechnical and
geoenvironmental applications
Geosynthetic Functions
•
•
•
•
•
•
•
Separation
Reinforcement
Stiffening
Filtration
Barrier
Drainage
Protection
Geosynthetic Types
•
•
•
•
•
•
•
•
•
Geotextiles
Geogrids
Geomembranes
Geonets
Geocomposites
Geocells
Geosynthetic clay liners
Erosion control products
Geo‐others:
o Geofibers
o Geofoam
o Geopipes
o HDPE vertical barriers
Geosynthetic Types
CE387C – Geoenvironmental Engineering
Prof. Jorge G. Zornberg
Department of CAEE
The University of Texas at Austin
Geotextiles
Geotextile: A permeable geosynthetic comprised solely
of textile (ASTM D4439)
Geotextiles are continuous sheets of woven, nonwoven, or
knitted fibers. The sheets are flexible and permeable and
generally have the appearance of a fabric.
Source: International Geosynthetics Society (IGS)
Source: Geosynthetic Institute (GSI)
Geogrids
Geogrid: Geosynthetic materials that have an
open grid‐like appearance
Geogrids are distinguished by the regular
network of tensile elements that form
openings that are large enough to interlock
with the surrounding soil matrix.
Source: International Geosynthetics Society (IGS)
Source: Geosynthetic Institute (GSI)
Geomembranes
Geomembrane: An essentially impermeable
geosynthetic composed of one or more
synthetic sheets (ASTM D4439)
They are continuous and flexible sheets used as
barriers to fluids, gases or vapors.
Source: International Geosynthetics Society (IGS)
Source: Geosynthetic Institute (GSI)
Geonets
Geonet: A geosynthetic consisting of integrally
connected parallel sets of ribs overlying
similar sets at various angles for planar
drainage of liquid or gases (ASTM D4439)
Source: International Geosynthetics Society (IGS)
Source: Geosynthetic Institute (GSI)
Geocomposites
Geocomposite: Geosynthetics made from a
combination of two or more geosynthetic
types
For example, prefabricated geocomposite drains formed by
a drainage core surrounded by a geotextile filter.
Source: International Geosynthetics Society (IGS)
Source: Geosynthetic Institute (GSI)
Prefabricated
Vertical Drains
Geocells
Geocells: Relatively thick, three dimensional
networks constructed from strips of polymeric
material
Strips are joined together to form interconnected cells that
are infilled with soil and sometimes concrete.
Source: International Geosynthetics Society (IGS)
Geocells
Geosynthetic Clay Liners (GCLs)
Geosynthetic clay liners: Prefabricated
bentonite clay layers incorporated between
geotextiles and/or geomembranes and used
as a barrier for liquid or solid waste
containment.
Bentonite
5-10 mm
Upper-GT
Reinforcing Fibers
GCL
Lower-GT
Courtesy: R. Brachman
Source: Geosynthetic Institute (GSI)
Erosion Control Products
Erosion Control Products: Minimize the
detrimental effect on soil caused by the
impact of rain and of surface water drainage
Some of these products are manufactured using
biodegradable products.
Source: International Geosynthetics Society (IGS)
Erosion Control Products
Source: Geosynthetic Institute (GSI)
Geo‐others
Source: Geosynthetic Institute (GSI)
Geosynthetic Functions
CE387C – Geoenvironmental Engineering
Prof. Jorge G. Zornberg
Department of CAEE
The University of Texas at Austin
Primary Functions
Geosynthetic applications can be classified
according to primary functions.
However, it is important to note that
geosynthetics may also perform one or
more secondary functions.
E.g.: Reinforcement + in-plane drainage
Design by Function
(a) Evaluate the criticality of the application;
(b) Determine the function(s) of the geosynthetic;
(c) Determine the required property value for the
function(s);
(d) Test or otherwise obtain the allowable property of
the candidate geosynthetic;
(e) Calculate the factor of safety (FS);
(f) Evaluate factor of safety;
(g) Prepare specifications and construction
documents; and
(h) Observe construction and post-construction
performance.
Source: Koerner (2012)
Separation Function
The geosynthetic, placed between two
dissimilar materials, maintains them apart to
keep their integrity and functionality.
Example: Geotextiles used to prevent
road base materials from penetrating
into underlying soft subgrade, thus
maintaining design thickness and
roadway integrity.
Key properties/characteristics:
• “Survivability” properties
Source: International Geosynthetics Society (IGS)
Separation Function
Transition Zone
of Intermixed
Material
(a) Without Geosynthetic Separator
(b) With Geosynthetic Separator
Source: Zornberg & Christopher (2007)
Reinforcement Function
The geosynthetic develops tensile forces
intended to maintain or improve the
stability of the soil‐geosynthetic
composite.
Example: Geogrids used to construct
embankments over very soft
foundation soils.
Key properties/characteristics:
• Ultimate tensile strength
Source: International Geosynthetics Society (IGS)
Reinforcement Function
Erosion control mat to promote vegetation
Stiffening Function
Geosynthetic allows the development of tensile
forces with the objective to control
deformations within a geotechnical system.
Example: A geotextile or geogrid used to
improve the mechanical properties of
the base material in a roadway.
Key properties/characteristics:
• Geosynthetic stiffness
• Soil‐geosynthetic interaction
• Confined stiffness of the soil‐geosynthetic
system under small displacement
Stiffening Function
Source: Zornberg & Gupta (2010)
Filtration Function
The geosynthetic allows water to flow across its
plane while retaining upstream fine soil
particles.
Example: Geotextiles used to prevent soils
from migrating into road drainage
aggregate or pipes while maintaining
flow through the system.
Key properties/characteristics:
• Apparent Opening Size (AOS)
• Permittivity
Source: International Geosynthetics Society (IGS)
Filtration Function
Source: Zornberg and Christopher (2007)
Filtration
Requirements:
1. Hydraulic Conductivity:
2. Soil Retention:
3. Long‐term flow compatibility:
Barrier Function
The geosynthetic minimizes cross‐plane flow,
providing containment of liquids or gasses.
Example: Geomembranes used as barrier to downward
movement of leachate at the base of a landfill.
Key properties/characteristics:
• Polymer type
• Thickness
Source: International Geosynthetics Society (IGS)
Barrier Function
Installation of a GCL in the
cover of an MSW landfill
Lining of a concrete dam
using geomembranes
Source: Geosynthetic Institute (GSI)
Lined Earth Dam:
Before Rip-Rap
Completed
Concrete
Dam Lining
Concrete Dam
Leaking!
Source: Geosynthetic Institute (GSI)
Drainage Function
The geosynthetic allows liquid (or gas) flow
within the plane of its structure.
Example: Prefabricated vertical drains (PVDs) used to accelerate
the consolidation rate of clay deposits.
Key properties/characteristics:
• Transmissivity
Source: International Geosynthetics Society (IGS)
Drainage Function
Geocomposite
drainage layer
being installed
over the barrier
system in the
cover of a MSW
landfill
Protection Function
The geosynthetic provides a cushion above or
below other material (e.g. a geomembrane) in
order to minimize damage during
construction or operation.
Example: Nonwoven geotextiles used to minimize puncture
of the geomembrane used in a landfill base liner,
avoiding direct contact with overlying gravel used in a
leachate collection system.
Key properties/characteristics:
• Resistance to puncture
• Thickness
protective geotextile
layer
geomembrane
Protection Function
Geomembrane
Compacted Clay
Nonwoven GT
Gravel
Installation of a nonwoven geotextile over the geomembrane of a
composite barrier at the bottom of a MSW landfill
Protection: Erosion Control
Geosynthetic acts to reduce erosion caused
by rainfall impact and water flow shear stress
For example, temporary geosynthetic
blankets and permanent geosynthetic
mats placed over the otherwise
exposed soil surface on slopes.
Source: International Geosynthetics Society (IGS)
Protection: Erosion Control
Slope showing advanced sheet and gully erosion
TRM
Design Procedures for Erosion Control in
Slopes and Channels
• There are several methods of estimating soil loss
• The most commonly used method in the US is USLE
(Universal Soil Loss Equation):
A = R  K  LS  C  P
where:
A = Computed soil loss (tons/acre or kg/hectare) for a
given storm period or time interval
R = Rainfall factor
K = Soil erodibility value
LS = Slope length and steepness factor
C = Vegetation or cover factor
P = Erosion control practice factor
• All factors, except C, do not vary more than one order of
magnitude. C changes several orders of magnitude
Geosynthetics: Summary
CE387C – Geoenvironmental Engineering
Prof. Jorge G. Zornberg
Department of CAEE
The University of Texas at Austin
Functions of Different Geosynthetics



















Summary
• Geosynthetics are geomaterials
• The number of geosynthetic types is large,
and growing
• Geosynthetics are engineered materials and,
as such, engineering properties are needed
for their design
• The properties of geosynthetics are selected
according to their functions (7 of them)
Major Organizations in
Geosynthetics
• International Geosynthetics Society (IGS)
www.geosyntheticssociety.org
• National chapters of the IGS (e.g., IGS‐NA)
• Geosynthetics Manufacturers Association
(GMA)
• Geosynthetic Institute (GSI)
• Erosion Control Technology Council (ECTC)
• ASTM & ISO Standards Organizations