Stabilization methods utilizing mineral-based materials are routinely availed in the remediation of contaminated land. The selection of appropriate mineral amendments is always an open field for research on the quest for the effective mixing proportions at an affordable cost. Geo synthetic Clay Liners (GCLs) comprises of a thin layer of Na-bentonite clay supported by one or two layers of geo textiles. In current years a significant increase of the geo-environmental applications for GCLs as contaminant barriers has been performed (Thiel et al., 1993). They have been widely availed in containment applications as part of composite liners for landfills and recently in attenuating metals from mining leachates (Wayne et al., 1998). Based on preliminary invittro research data and a pilot scale application, a new type of geocomposite was designed and trial produced as an innovative, commercial product under the term Geosynthetic Reactive Clay (GRC) for toxic metal retention in contaminated land.

1. Geocomposite and Its Influence in
Environment
BY
Dr. SREEREMYA.S
FACULTY OF BIOLOGY

2. • Stabilization methods utilizing mineral-based materials are routinely
availed in the remediation of contaminated land. The selection of
appropriate mineral amendments is always an open field for research on
the quest for the effective mixing proportions at an affordable cost. Geo
synthetic Clay Liners (GCLs) comprises of a thin layer of Na-bentonite clay
supported by one or two layers of geo textiles.
• In current years a significant increase of the geo-environmental
applications for GCLs as contaminant barriers has been performed (Thiel
et al., 1993). They have been widely availed in containment applications as
part of composite liners for landfills and recently in attenuating metals
from mining leachates (Wayne et al., 1998). Based on preliminary invittro
research data and a pilot scale application, a new type of geocomposite
was designed and trial produced as an innovative, commercial product
under the term Geosynthetic Reactive Clay (GRC) for toxic metal retention
in contaminated land.

3. • Greece and typically was a reference project for the trial production of the designed geo composite.
According to the site proposed remediation actions, the general construction section included:
• a) ex-situ excavation of the contaminated soil to a depth of 50 cm,
• b) Placement of the designed GRC product over the contaminated soil and finally
• c) Placing of strata of vegetal soil above the GRC for cover purposes, according to the landscape
design.
• The GRC geo composite consists of a thin layer of permeable, attapulgite clay sandwiched between
two starts of non-woven geo textiles (Triplett et al., 2001). The desired gradation of the attapulgite
clay was prepared industrially aiming specifically to act primarily as a filter.
• Based on the design principles and the proposed environmental applications of GRC, the hydraulic
properties of at tapulgite clay and geo textiles allow the downwards movement of water during
rainfall or irrigation (Terzaghi, 1964). In addition to its hydraulic properties, the attapulgite clay in
the GRC product has been justified as an effective binder for sorption/ adsorption of toxic metals,
having a main role of preventing upwards migration of metals through evaporation from the
contaminated soil to the emplaced, non contaminated vegetal soil. The non-woven geo textiles
ensure the encapsulation and typically filter functions. Environmental applications of attapulgite
clay as an effective toxic Optimization of a gradations for the optimization of the “GRC” product

4. • New TYPE OF GEOCOMPOSITE FOR ENVIRONMENTAL
APPLICATIONS Based on preliminary in vitro research
data and a pilot scale application, a new type of geo
composite was designed and trial produced as an
innovative product under the term Geo synthetic
Reactive Clay (GRC) for environmental applications. The
GRC type geo composite comprises of a thin layer of
permeable, attapulgite clay sandwiched between two
layers of non-woven geo textiles (Yoshida et al., 2006).
• The results of an extensive laboratory scale
investigation of the physical, hydraulic and geochemical
properties of natural and modified attapulgite clay
samples in various selected

5. • The effectiveness of GRC for toxic metal retentions was
previous studied in the laboratory by up flow
percolation tests in testing columns that were designed
and packed with the availed materials (contaminated
soil, geo textiles, attapulgite clay and vegetal soil)
according to the proposed design, by availing different
geometry for the trial produced GRC(Faure et al.,2002).
Besides, the long-term behavior of the GRC at the pilot
scale field concerning its effectiveness for toxic metal
retentions, was researched by post monitoring data of
the vegetal soil quality over two years period that
indicated there was no effect by the contaminated
underlying soil(Richardson et al.,2005).

6. • Geo textiles are the geo synthetic product generally
availed in filtration (Zhao et al., 1999). Both adequate
hydraulic conductivity (provided by a geo textile with a
relatively open structure) and adequate soil retention
(garnered by a geo textile with a relatively tight
structure) should be offered by the selected product
(Zorn berg et al., 2002). In addition, considerations
should be typically made regarding the long-term soil-
to-geo textile flow compatibility such that the flow
through the geo textile will not reduce excessively by
clogging during the lifetime of the system (Budka et al.,
2007).

7. • The geo synthetic-to-soil system should then achieve
an equilibrium that allows for adequate liquid flow
with limited soil loss across the plane of the geo textile
over a service lifetime compatible with its application
under consideration. Filtration concepts are
systematically established in the design of soil filters,
and similar concepts can be used in the design of geo
textile filters. The flow of liquid is perpendicular to the
plane of the geo synthetic and, consequently, filtration
mainly refers to the cross-plane hydraulic conductivity.
Some of the geo synthetics used for this purpose are
relatively thick and compressible (Richardson et al.,
2004).

8. • Testing procedures for geo textile permittivity follow
similar guidelines availed for testing soil hydraulic
conductivity. Some designers prefer to work directly
with hydraulic conductivity and require the geo textile
hydraulic conductivity to be multiple of the adjacent
soil’s hydraulic conductivity9Faure et al., 1993). As the
flow of liquid through the geo textile aggrandizes, the
geo textile voids should be larger. However, large geo
textile voids can lead to an unacceptable situation
called soil piping, in which the soil particles are
continuously carried through the geo textile, leaving
large soil voids behind (Richardson et al., 2003).

9. • The liquid velocity then aggrandizes which accelerates the process and may lead to
the collapse of the soil structure (Faure et al., 1994). This process can be prevented
by selecting a geo textile with voids small enough to retain the soil on the
upstream side of the fabric (Hall et al., 2007). It is the coarser soil fraction that
must be primarily retained. The coarser-sized particles eventually filter the finer-
sized particles and build up a stable upstream soil structure.
• Different approaches have been developed for soil retention design using geo
textiles; most of them compare the soil particle size characteristics to the 96%
opening size of the geo textile (defined as O95ofthe geo textile). The test method
used in the United States to determine the geo textile opening size is called the
apparent opening size (AOS) test (Zorn berg et al., 2007). Some of the soil particles
will embed themselves on or within the geo textile structures and will cause
reduction in the hydraulic conductivity or permittivity of the geo textile. Although
some partial clogging should be mainly expected, the designer should ensure that
the geo textile will not excessively clog. That is, the flow of liquid will not be
decreased to a point at which the system will not adequately perform its function
(Richardson et al., 2002).

10. REFERNCE
• Journal of Remote Sensing, GIS &
Geotechnical Engineering, Geocomposite and
Its Influence in Environment, S.
Sreeremya,2018.Vol(3):3,1-9.