For quite some time, geotextiles have been making their way into the growing civil engineering
sector. Their most important requirement is permanent functionality, which can be achieved by using
different kinds of fabric structures.
Geotextiles have to fulfill a lot of demands. A major requirement is strength in both machine
direction (MD) and cross direction (CD) in order to provide stability under the mechanical stress
caused by debris and construction operations.
In 2008, the man-made Palm Jumeirah Islands were opened in Dubai. Today, there are big
problems at the site, most probably because of inferior quality geotextiles.
Different Fabrics For Different End-uses
Geotextiles are one of the oldest forms of textile construction. Ancient Egyptians used reed
mats for armoring banks and buildings. In the beginning, geotextiles were made of woven fabrics.
Today, fabric constructions like nonwovens, or knitted fabrics such as warp knits or nets –
so-called geogrids – also are used more.
According to Johann-Philipp Dilo, owner and chairman of the DiloGroup, Germany, North America
and Europe currently are his business’s largest geotextile markets: “The geotextiles segment is one
of our key markets for the production of complete needlepunch production lines.”
Durability And Efficiency
As mentioned above, geotextiles have to comply with a lot of requirements. Permanent
functionality is essential for separation or filtration purposes. If the specifications are not
achieved, the risk of failure of the whole system is possible. The main functions of geotextiles
are separation, filtration, drainage, protection and reinforcement, and erosion control.
Separation
As a separating layer, geotextiles prevent the intermixing of adjacent soils or fill
materials. Materials used are mainly nonwovens, woven fabrics and composite materials made of
synthetic polymers. Selection of the right textile product depends on the grain size of the base
course material and the anticipated loads during construction.
Dilo said most durable needlepunched nonwovens are made of polyester (PET) or polypropylene
(PP). “On top of that,” he said, “recycled fiber types, such as fibers made from PET bottle chips,
are possible and quite common.”
For degradable needlepunched nonwovens, it is possible to process virtually all natural fiber
materials, which are chopped to a selected length.
Filtration
This application is probably the most important one: Water pressure is one of the main
reasons for damaged walls, dams or other man-made barriers. As a filter, the geotextile holds back
soil components or other particles to allow the free flow of water. One has to distinguish between
the mechanical strength for soil retention and the hydraulic filter effectiveness with the goal of
low pressure drop for water drainage. Therefore, the geotextile’s thickness plays an important, if
not decisive, role and has a great influence on long-term, mechanical and hydraulic filter
effectiveness.
Geotextiles is a key market for the Dilo Systems Hyperline, which comprises a complete
needlepunch production line.
Drainage
For drainage, geotextiles play more or less the same role as in filtration to discharge rain,
groundwater or other liquids. Drainage systems are offered as individual components or as composite
elements comprising at least one filter layer and a drainage layer. Runoff should be removed
without pressure loss in the drainage layer. Geotextile drainage systems can replace traditional
concrete or plastic tube constructions.
Protection And Reinforcement
Protection and reinforcement are very important geotextile functions for prevention of
mechanical damage to inbuilt material, such as sealing stripes or coated material. Nonwovens and
composites can be used as protective layers. For the protective function, important properties
include drift punch and puncture resistance, as well as the element layer and geotextile surface
thickness. Protective geotextiles are used in landfills and tunnels to protect impermeable
material.
Installed under or between soil layers, reinforcing geotextiles pick up and absorb tensile
forces to improve the soil layer mechanical properties. They are applied mainly as nonwovens or
geogrids as supporting structures for the stabilization of dams on unstable ground. Reinforcements
can save a lot of money because complicated constructive measures can be avoided.
Erosion Control
Geotextiles for erosion control are often installed in the same environments as protection
and reinforcement geotextiles. Erosion control geotextiles help to quickly stabilize embankments,
whereas plants need a lot of time to grow their roots.
Karl Mayer Malimo’s RS MSUS-V raschel machine can produce new high-tensile-strength geogrids
suitable for mining applications.
Quality Above All
A lot of requirements must be met to achieve the specified properties. “Virtually all
components from our portfolio from fiber preparation, carded web forming with crosslapper up to
needlepunching are particularly well-suited for geotextiles to guarantee a reproducible and even
quality,” Dilo said. “Our customers want to have the whole production process in their hands to
have total control over the quality of the finished product. Geotextiles made of needlepunched
nonwovens provide value for money, have a good price/performance ratio, and combine strength with
elasticity.”
How important is the finishing of geotextiles? “In particular, the heat-setting process is
very important for the quality,” Dilo said. “This process contributes to an additional increase in
strength, and is therefore coming to be more in demand.”
Geogrids
Geogrids are gaining more ground in the markets thanks to the permanent evolution of the
production process. They are used in construction for reinforcement applications including:
separation of adjacent soil types; filtration to remove solid components; liquid absorption over a
broad expanse; soil erosion prevention; mechanical protection; and soil stabilization in road and
bridge construction, laying of railroad tracks, and dam and dyke construction; to name a few
applications. Depending on end-use, geogrids feature various mesh sizes to distribute static and
dynamic loads into the subsoil.
New Raschel Machine
Karl Mayer Malimo, Germany, recently introduced the RS MSUS-V rachel machine featuring
parallel weft insertion and web feed-in facility, which can be used to manufacture a new geogrid
type that is suitable for mining applications. These geogrids have a tensile strength of 1,000
kiloNewtons in both the weft and zero inlay directions, and comply with the DIN EN ISO 10319
standard. They feature a raw fabric weight of 3,300 grams per square meter, high-strength PET
construction and flame-resistant coating.
The new geogrids are used to stabilize a mine’s roof and sidewalls and provide protection
from rock falls. They were developed using a RS MSUS-V machine with a gauge of E 3 and a 213-inch
working width. Karl Mayer Malimo reports the machine can process glass rovings, basalt and all PET
fiber counts; and can produce a wide range of constructions. Capabilities include the ability to
incorporate layers of webs to produce composites in one step. Within the composites,
direction-oriented yarns having a specified tear strength provide support and reinforcement, while
the webs provide erosion protection, separation and filtration.
Promising Future
Geotextiles save a lot of concrete, transport costs and labor. However, if one wants to be
successful in this promising market, the production site should be close to the region where the
geotextiles will be used, mainly because of very high material transport costs.
“Geotextiles are tailor-made products,” said Dilo. “It’s first the product and then the
price. Geotextiles have a bright future.”
July/August/September 2012