advancement in geotechnical engineering with geofoam
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Govt. College Of Engineering ,Amravati .
National Level Technical Paper
On
Group - 1
Geotechnical Engineering
“ ADVANCEMENT IN GEOTECHNICAL
ENGINEERING WITH GEOFOAM ”
Submitted By
Mr. Jagdish S. Billore Miss. Deeksha K. Gupta
([email protected]) ([email protected])
(3rd Civil Engg.) ( 3rd Civil Engg.)
Department of Civil Engineering
Govt. College of EngineeringAmravati-444604
(Maharashtra)
“ADVANCEMENT IN GEOTECHNICAL ENGG. WITH GEOFOAMS”
ABSTRACT
Polymeric (plastic) and glass foams have been used in geotechnical
applications as thermal insulation, lightweight fill, and for many other functions.Any type of
foam used in a geotechnical application has been considered to be a geosynthetic product
called "geofoam." This new terminology coincided with a rapid expansion worldwide in the
knowledge and use of foams in geotechnical applications. The primary focus of this paper is
to list geofoam research and development needs to support the continued growth of geofoam
technology. A brief overview of geofoam materials, and past and current uses of geofoam is
also included to provide background information for understanding these research and
development needs.
1. What is Geofoam?
Geofoam is the generic name for any foam material used in a geotechnical (on- or in-
ground) application. Geofoam is now recognized worldwide as a geosynthetic product
category in the same sense as geotextiles, geomembranes, geogrids, etc.
2. FUNCTIONS OF GEOFOAM
Following are the specific function of geofoam
Unique functions. With one exception (drainage), geofoam functions do not duplicate
those of any other geosynthetic product. Therefore, geofoam provides the end user
with new tools for solving geotechnical problems.
Multi-functionality. Depending on the material and product used, geofoam can be
inherently multi-functional. This increases its cost-effectiveness in many applications
because several technical and financial benefits can be derived from using only one
product.
Complementary. Geofoam products are rarely used alone. In most geofoam
applications, one or more other types of geosynthetics are used. In some cases, the
other geosynthetic (e.g., a geotextile) is actually a part of a geofoam-based
geocomposite as in various drainage products and the Geoinclusion. Therefore,
geofoams complement the use of other geosynthetic products.
Synergy. Geofoam products allow the use of other types of geosynthetics (especially
geogrids and other tensile-reinforcement products) in applications where these other
geosynthetics were heretofore of little or no use. Therefore, there are applications
where geofoam and other types of geosynthetics can be combined synergistically to
produce new, unique results that would not be possible otherwise.
3. MATERIALS
Most geofoam materials are polymeric (plastic) but glass foam (cellular glass)
has been and is also used. Although gases (called blowing agents) other than air are typically
used in manufacturing geofoams, with time (which can vary widely depending on the
geofoam material, the cells eventually become filled with air.
Polymeric materials have always dominated the geofoam market. Several different
polymers have been tried in geofoam applications but the one used most commonly by far is
polystyrene. There are two ways to manufacture polystyrene foam:
1. Expanded polystyrene. (EPS)
2. Extruded expanded polystyrene (XPS)
EPS Geofoam is generally left in its natural white color and XPS geofoam is colored either
blue, green, pink, or yellow depending on the manufacturing.
3.1 Products
3.1.1 Expanded Polystyrene (EPS)
There are two primary methods for molding EPS:
a) Block molding which produces finished prismatic blocks that are typically 500 mm to
600 mm high, 1000 mm to 1200 mm wide, and 2000 mm to 5000 mm long. These blocks can
be cut into panels or pieces of various shapes for specific applications where There is
significant potential for using geofoam panels as facing for thin retaining walls (in the way
that precast concrete panels are used now) and as blocks in segmental retaining walls (SRWs)
in a way that concrete blocks are used . The full-size blocks are neither required or desired.
Products that result are called "EPS-block geofoam." This is the predominant type of EPS
geofoam and predominant geofoam product overall worldwide.
b) Custom shape molding produces pieces with specific shapes. In non-geofoam
applications common examples include the white foam coffee cup and the cushion packaging
used around consumer electronics and appliances. Shape-molded EPS products for geofoam
applications (called "EPS-shape geofoam") were rare until the last few years
There is a variation on block molding called slab molding in which relatively thin
panels are produced directly, with a custom shape so that it is actually a slab-shape hybrid.
Such products for geofoam applications are relatively rare because of the highly specialized
molding equipment required. In addition, there are other niche geofoam materials such as
glued or molded polystyrene porous block and elasticized EPS block
Geocomposite products that utilize EPS as a component are becoming increasingly
common. One example is the Geoinclusion, which is available in North America. This
product uses a panel of elasticized-EPS-block geofoam as its primary component plus a
drainage geocomposite that is factory laminated to one face of the panel.
3.2.1 Extruded Polystyrene (XPS)
XPS is produced primarily in plank-shaped pieces. It is possible to custom-extrude a
particular shape but the distinction between planks and shapes in geofoam terminology is not
done (at least to date) as it is for EPS.
3.2.2 Durability
Durability of geosynthetics in general has been a subject of great interest in recent
years. Overall, the durability of EPS and XPS geofoams is excellent. . Typically, the only
concern with EPS and XPS geofoams is that they be protected from gasoline and similar
petroleum-hydrocarbon liquids with a geomembrane or similar barrier in applications where
there is a potential for a fuel spill (e.g., road embankments).
In addition, in some applications (thermal insulation around the below-ground
space of buildings is one in particular) there have been problems with infestation by certain
burrowing insects (termites, carpenter ants). It appears that an effective passive treatment
against potential insect infestation has been developed for EPS-block but not XPS.
4. FUNCTIONS AND THEIR APPLICATIONS OF GEOFOAM
4.1 Thermal Insulation
EPS and XPS were invented circa 1950 primarily to provide thermal
insulation. Foams are very efficient thermal insulators because they are approximately 98%
to 99% gas by volume and gases are typically very efficient thermal insulators. Therefore, it
is the first known application call geofoam was as thermal insulation of roads, railways, and
airfield pavements (to prevent or at least reduce seasonal frost heaving or retard thawing in
permafrost areas); the below-ground portions of buildings (to reduce seasonal heating
requirements); and beneath on-grade storage tanks containing cold liquids (one of the few
applications where glass foam is used almost exclusively) .
Pavement construction cost as reflected in the protection offered against frost
heaving. When insulated pavements were first used, they were designed to provide full
protection against frost penetration into the subgrade beneath the geofoam and concomitant
frost heaving. Some later designs allowed partial frost penetration of the subgrade, primarily
as an economy measure. All geofoam materials absorb ground water with time and this
reduces their thermal resistivity so should be accounted for in design.
4.2 Lightweight Fill
Geofoams, especially polymeric ones, are unique materials they have a
density only about 1% to 2% of the density of soil and rock are sufficiently strong to support
many types of loads encountered in geotechnical applications. The earliest functions of
geofoam that was developed was its use as a lightweight fill material in a wide variety of
"earthworks." The benefit of using geofoam as opposed to other materials in earthworks is
the significantly reduced stresses on the underlying subgrade. This can have multiple benefits
in terms of reduced settlements, increased stability, light weight fill material under highway
(shown in fig.)
Fig-1 -Light weight fills materials under Highway.
4.3 Compressible Inclusion
One of the very useful aspects of EPS-block geofoam is that it can be manufactured
over a range in densities. This is relevant because if EPS block is manufactured to certain
quality standards then (and only then) can density be a useful index property in the same way
that particle size of granular soils or Atterberg Limits of plastic soils are useful index
properties of soils. Applications fall into two broad categories:
Earth retaining structures where horizontal arching is involved.
Pipes, culverts, and similar structures where vertical arching is involved E.g.
Geofoam in landscaping (fig)
Fig-2 –Geofoam use in landscaping
4.4 Drainage
Geofoam materials have very low permeability for fluids (both gases and
liquids). However, both EPS and XPS geofoam products can be factory cut or purposely
shape molded to have a geometry such that they readily transmit fluids (especially ground
water) along one face or side of the product. This has been extended to EPS-shape products
intended to readily transmit ground-borne gases such as methane and radon.
There are geofoam materials that have an inherent permeability throughout
their entire thickness. The most-common example is glued polystyrene porous block. This
panel-shaped product uses expanded spheres of polystyrene that are glued into an open
matrix. One face of the panel is typically covered with a geotextile which provides separation
and filtration functions. In general, geofoam products are not cost effective compared to other
drainage geocomposites when only drainage is required
4.5 Damping
The inherent very low density yet significant stiffness of geofoam can be
beneficial in reducing ground-borne, small-amplitude waves that produce noise or ground
motion that may be disturbing to people and/or harmful to sensitive equipment. Typical
sources of such vibrations are motor vehicles or trains. It should be noted that for vibrations
of large amplitude, such as from earthquakes, where relatively large movement of the ground
(i.e., soil particles) is involved, the benefit of using geofoam appears to derive more from the
compressible-inclusion function rather than the damping function.
The first use of geofoam, specifically, EPS block, to reduce small-amplitude
vibrations is unclear, but papers and magazine articles on the subject have been found as far
back as the 1980s. Regardless of its origin, this is arguably the least studied and utilized
geofoam functions to date.
4.6 Structural
In this category are those applications where the geofoam is either serving as a
structural element or some application that does not clearly fit into another functional
category. The application of using geofoam panels as facing for thin retaining walls (in the
way that precast concrete panels are used now) and as blocks in segmental retaining walls
(SRWs) in that way that concrete blocks are used now.
5. Technology advancement (research and development)
5.1 Material Testing and Constitutive Models
A study of stress-strain behavior, especially under creep conditions, for
temperatures greater than those typically encountered in a laboratory environment
(approximately +23C). The elevated temperatures selected for testing should reflect the upper
range of average annual air temperatures found in the warmest climates of the Earth. This is
particularly relevant because it is in such areas such as Southeast Asia where much of the
growth of Geofoam usage, particularly for lightweight fill applications, is likely to occur. It is
the opinion that the current body of laboratory test data and case history experience
(overwhelmingly in relatively cool climates) may not be wholly appropriate because the
creep of polymeric Geofoam is known to increase with increasing temperature.
A fundamental evaluation of the behavior under relaxation (stress reduction
with time under constant strain) is required. To date, relaxation behavior has been inferred
from mathematical manipulation of creep-test data but this needs verification using the results
of explicit relaxation testing before it can be used with confidence in practice.
It is strongly suggested that that atmospheric (barometric) pressure be
recorded during all future tests, especially those of extended duration such as creep and
relaxation. Unpublished relaxation tests performed by the author suggest that the air pressure
inside the cells of EPS lags atmospheric pressure changes. Thus depending on the relative
pressure change, the EPS can appear to be temporarily stiffer or softer than some average
value because of differential pressures across the cell walls. This phenomenon, which was
encountered unexpectedly by the author, requires further study. Also in VNIT college,
Nagpur (during 1996-99) research were made on Reduction of swelling pressure using
Geofoam by Proff.P.B.Daigwane (Phd. in geosynthesis).
REFERENCES
1. Research work on reduction of swelling pressure using geofoam ,by
Proff.P.B.Daigwane(Phd. in geosynthesis)
2. Horvath, J.S. (1995). Geofoam Geosynthetic, Horvath Engineering, P.C., Scarsdale,
N.Y., U.S.A., 217 pp.
3. Horvath, J.S. (1996a). "The Compressible Inclusion Function of EPS Geofoam: An
Overview," to be presented at the International Symposium on EPS Construction
Method (ISEPS Tokyo '96), Tokyo, Japan, October.
4. Horvath, J.S. (1996b). "The Compressible Inclusion Function of EPS Geofoam,"
Geotextiles and Geomembranes, in press.