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

(billore12@yahoo.com) (deekshadk@yahoo.com)

(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.