Transcript Introduction to Cellular Geosynthetics

Introduction to Cellular Geosynthetics
(Geofoams and Geocombs)
A Manhattan College Center for Geotechnology
Technology Transfer through Distance Learning Program
Educational Product
Presentation prepared by
John S. Horvath, Ph.D., P.E.
Professor of Civil Engineering
Director/Center for Geotechnology
Manhattan College
School of Engineering
Bronx, New York, U.S.A.
© 3 September 2001 by John S. Horvath. All rights reserved.
Construction Material Changes
• improvements to traditional materials (steel and PCC)
• development of new functions (roles) and applications
for existing materials
• development of new materials
• use of recycled waste materials
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Construction Material Changes
• improvements to traditional materials (steel and PCC)
• development of new functions (roles) and applications
for existing materials <<< geocombs and some geofoams
• development of new materials <<< some geofoams
• use of recycled waste materials <<< some geofoams
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Geofoam ...
Generic term for any closed-cell foam used in a
geotechnical application that is manufactured either in a
fixed plant or in-situ from an expansion process using a
blowing agent:
• polymeric (plastic)
– polyethylene (PE)
– expanded polystyrene (EPS) <<< predominant
– extruded polystyrene (XPS)
– polyurethane (PUR)
• glass (cellular glass)
• cementitious
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EPS block in temporary storage after molding.
The entire block weighs less than the person handling it!
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Example of one of at least three different designs of
EPS-shape geofoam "anti-buoyancy" blocks
developed in Japan (dimensions in millimetres).
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Geocomb ...
… the newest "geo" material (geosynthetic), formerly
referred to as "structures alveolaires ultra légères"
(SAUL) or "ultra light cellular structures" (ULCS) in
France where it was developed and has been used since
the 1980s.
… defined as an open-cell (honeycomb shaped in crosssection) polymeric (PP, PVC) material created by an
extrusion process. Typically supplied as a panel- or blockshaped final product.
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typical tube (~ 25 mm/1 in)
PP (left) and PVC (right) geocombs.
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Benefits of Using Geofoams and Geocombs
• efficient use of solid material
• work with the forces of nature, not against them
• can be useful for both new construction and with
existing structures, permanent and temporary, all
climates/weather, "good" and "poor" ground
• provide unique geosynthetic functions
• can be multifunctional in many applications
• compatible and synergistic with other types of
geosynthetics
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Overview of Design Process
• design by function to identify desired properties
• define parameters for desired analyses and obtain
relevant technical information for these parameters
• generally treat as an equivalent earth material and
use conventional geotechnical analytical methods
• economic assessment (construction + O&M)
• relevant standards and specifications
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Geosynthetic Functions
• thermal insulation (1960s) >>> geofoams only
• lightweight fill (1970s) >>> geofoams & geocombs
• drainage (1970s) >>> geofoams & geocombs
• noise/vibration damping (1980s) >>> geofoams only
• compressible inclusion (1980s) >>> geofoams only
• structural (1990s) >>> geofoams only
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Important Aspects of Material Behavior and
Other Technical Issues for Design
• index properties
• mechanical (stress-strain-time) behavior
• thermal properties
• constructability and safety
• durability
• environmental impact
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Factors to Consider in an Economic Assessment
• design aspects of initial construction
• constructability aspects of initial construction
• reduced costs of operation and maintenance
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Standards and Specifications
• standards constitute technology documentation
and are the foundation of any technology
• specifications are the project-specific
application of relevant standards to define the
minimum acceptable results in a given application
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Thermal Insulation Benefits
• life-cycle energy cost savings
• construction cost savings
• improved geotechnical/structural performance
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Thermal Insulation Applications
• buildings and storage tanks (all climates)
• landfill liners (all climates)
• shallow buried structures (all climates)
• earth retaining structures (cold climates)
• pavements and railways (cold climates)
• underground conduits (cold climates)
• shallow foundations (cold climates)
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Test of landfill-liner thermal insulation alternatives in the U.S.A.
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geofoam
drainage layer
Use of geofoam behind an earth retaining structure to prevent
seasonal freezing of the wall drainage system and retained soil.
Note that the drainage system could be incorporated into the
geofoam product for overall increased efficiency and reduced cost.
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Rebuilding an existing road in Norway with geofoam insulation.
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Rebuilding an existing railway in Norway with geofoam insulation.
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geofoam
depth of seasonal
freezing
normal conduit depth
Use of geofoam above an underground conduit to locally modify the
depth of seasonal freezing to allow shallower conduit embedment.
Note that the geofoam could also be designed to act as a
compressible inclusion to reduce forces acting on the conduit.
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geofoam
depth of
seasonal
freezing
footing depth
without insulation
Typical Frost Protected Shallow Foundation concept application.
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Lightweight Fill Applications
• embankments and fills:
 transportation
 water resources
 foundation support
 architecture and landscaping
• earth retaining structure backfill and fills
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Rebuilding a failed road embankment in the U.S.A.
in the winter using EPS-block geofoam.
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Spraying a PCC facing on a "geofoam wall" type road fill
in the mountains of Japan.
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Constructing an EPS-block geofoam road embankment in Norway
for a combined bridge approach fill and bridge abutment foundation.
Note the wooden formwork for the abutment footing.
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Using EPS-block geofoam to construct an abutment backfill
for a new road bridge in Chile.
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Completed approach embankment and abutment backfill
using EPS-block geofoam for a new road bridge in Canada.
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Constructing an approach embankment and abutment backfill
using geocomb blocks for a road bridge in France.
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Rehabilitating and raising a levee in the U.S.A. using EPS-block geofoam.
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Building basement wall in the U.S.A. backfilled using EPS-block geofoam.
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Anchored bulkhead in Japan partially backfilled
using EPS-block geofoam.
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Barbed connector plates used between blocks of EPS geofoam
in Japan (dimensions are in millimetres, 25 mm = 1 in).
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100 mm (4 in) square barbed connector plate
used between blocks of EPS geofoam in the U.S.A.
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Drainage Applications
• fluid transmission using geofoams:
 ground water around below-grade structures
 ground water behind earth retaining structures
 leachate collection systems in landfills
 ground-borne gases around below-grade structures
• fluid transmission and storage using geocombs
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EPS-shape geofoam product developed in the U.K. specifically for
collecting and draining ground-borne gases such as methane and
radon. Note that it also provides thermal insulation for the structure.
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glued polystyrene porous block
high-permeability core
Geofoam drainage geocomposite available in Asia, Europe and the
U.S.A. that uses a glued polystyrene porous block core.
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Geofoam sheet-drain product composed of pieces of
recycled PE that was developed in The Netherlands.
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Drainage (fluid transmission and storage) applications
using geocomb panels and blocks developed in France.
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Noise and Vibration Damping Applications
• attenuation of small-amplitude, ground-borne
vibrations from:
 motor vehicles
 trains
• attenuation of noise from trains
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EPS-block geofoam
PCC slab
EPS-block geofoam
EPS-block geofoam used to dampen noise and vibrations from a
railway in Germany . The EPS blocks directly beneath the tracks are
also acting as a lightweight fill for the clay ("Ton") subgrade.
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EPS-block geofoam
PCC ties (sleepers)
PCC layers
EPS-block geofoam used to dampen noise and vibrations
from light-rail vehicles (trams/trolleys) in France and Germany.
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Compressible Inclusion Applications
• lateral earth pressure and settlement reduction:
 shear-strength mobilization of "normal" soils
 volume change of expansive/freezing soil/rock
 structure movement
• vertical stress reduction from expansive soil/rock
• vertical arching above underground conduits
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geofoam
soil movement
tensile reinforcement
(optional)
Use of geofoam compressible inclusion behind a rigid/non-yielding
earth retaining structure to reduce lateral earth pressures
(optional use of geosynthetic tensile reinforcement also shown).
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Use of a resilient-EPS geofoam geocomposite in the U.S.A. to act as a
compressible inclusion to accommodate integral-abutment bridge
movement. Drainage is also provided by the same product.
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geofoam
ground movement
ground movement
ground movement
Use of a geofoam compressible inclusion around
foundation elements of a structure to
reduce stresses in expansive ground (soil or rock) conditions.
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EPS-block geofoam used as a compressible inclusion around a
reinforced-PCC grade beam in expansive soil in the U.K.
(geofoam also served as formwork during construction).
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EPS-block geofoam used as a compressible inclusion beneath a deepfoundation supported tunnel base slab in expansive ground in the U.K.
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EPS-block geofoam product used as a compressible inclusion beneath
a deep-foundation supported base slab of a building in Canada
(similar product also developed in U.K.).
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geofoam
ground movement
ground movement
Use of a geofoam compressible inclusion above an
underground conduit to reduce vertical stresses acting on the
conduit by inducing vertical arching within the overlying soil.
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Multifunctional use of a geofoam geocomposite only ~ 150 mm (6 in)
thick simultaneously providing compressible inclusion, drainage and
thermal insulation behind a building basement wall in the U.S.A.
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Structural/Miscellaneous Applications
• forms for PCC walls
• MSEW facing panels
• void formers for PCC slabs
• crash barriers for motor vehicles and aircraft
• impact cushioning for rock sheds
• void filling and foundation remediation
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Panels cut from block-molded EPS used as formwork for a reinforcedPCC basement wall in the U.S.A. The EPS also provides postconstruction thermal insulation for the life of the structure.
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MSEW system developed in the U.K. with geogrid reinforcement
and facing panels cut from block-molded EPS.
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two-part stucco-like
finish
EPS
mesh reinforcement
underlayment
Generic components of EIFS technology used over EPS and XPS
to create a wide variety of durable architectural finishes.
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Block-molded EPS used as a lightweight void former for a
pile-supported structural slab constructed over a soft subgrade
in the U.S.A.
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EPS blocks
Credit: Paul Arch Racing Photos
EPS blocks used as crash-cushioning barriers around an auto-racing
track in the U.S.A. Note evidence of extensive prior collision damage.
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EPS blocks
EPS blocks used as protection for PCC rock sheds in
mountainous areas in Europe and Japan.
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