In modern civil engineering, seepage prevention and reinforcement are crucial to ensuring project safety and durability. Composite geomembrane, as an efficient composite geosynthetic material, with its unique structure and excellent performance, has become an indispensable material in various fields such as water conservancy, environmental protection, and transportation. This article will take you deep into the world of composite geomembranes.What is a Composite Geomembrane?
A composite geomembrane is a geosynthetic
material formed by laminating a geotextile to one or both sides of a geomembrane through specific processes. Its main purpose is to use the
geotextile to protect the central impermeable geomembrane from damage while
simultaneously performing multiple functions such as drainage and
reinforcement.
Depending on the structure, composite
geomembranes are mainly classified into one cloth one membrane, two cloths one membrane (also
called two fabrics one membrane), and even one cloth two membranes and multiple
cloths multiple membranes. For example, "SN2/PE-16-400-0.5" indicates
a composite of two layers of short-filament geotextile (SN2) and one layer of
high-density polyethylene membrane (PE), with a tensile strength of 16KN, a
total weight of the two geotextile layers of 400 grams, and a HDPE membrane
thickness of 0.5 millimeters.
Outstanding Characteristics of Composite
Geomembranes
Composite geomembranes combine the
advantages of geotextiles and geomembranes. Their main performance
characteristics include:
- Excellent Impermeability: The
central plastic film (mainly HDPE, LDPE, PVC, or EVA) provides a reliable impermeable barrier,
effectively preventing the leakage of liquids and gases.
- High Strength and Tear Resistance: The composite structure gives it excellent physical and
mechanical properties such as tensile
resistance, tear resistance, puncture resistance, and burst resistance, enabling it to withstand various stresses during construction
and operation.
- Chemical Corrosion Resistance and Aging Resistance: Made from polymer materials with added anti-aging agents, it
is resistant to acids, alkalis, corrosion, and UV aging. It has a long service life and can adapt to unconventional
temperature environments.
- Drainage and Filtration Functions: The geotextile layers on both sides not only protect the
membrane material but also form drainage
channels, allowing water to drain along its interior while preventing
soil particle loss, acting as a filter.
- High Friction Coefficient:
Compared to a simple geomembrane, the non-woven fabric in the composite
geomembrane provides a higher friction coefficient, effectively preventing the covering layer from sliding and increasing engineering stability.
Main Application Fields of Composite
Geomembranes
Due to their comprehensive performance,
composite geomembranes have a wide range of applications:
- Water Conservancy Projects: They
are the preferred material for anti-seepage treatment in dams, reservoirs, channels,
etc., preventing water loss and seepage damage to dam structures.
- Environmental Protection Projects: Widely used for anti-seepage and anti-pollution treatment in domestic waste landfills, industrial solid waste landfills, and
sewage treatment plants, preventing harmful
leachate from contaminating soil and groundwater.
- Transportation Engineering: Used
for waterproofing and moisture prevention of road and railway
subgrades, tunnel lining drainage, and
solving problems of soft foundation reinforcement and slope protection.
- Municipal, Industrial, and Agricultural Engineering: Commonly used for anti-seepage in artificial lakes, landscape water systems, storage ponds,
aquaculture ponds, as well as anti-seepage treatment for petroleum storage tank foundations,
mining heap leach pads, and agricultural irrigation channels.
- Other Fields: Can also be used in salt field crystallization ponds, ash dams in the power
industry, airport runway foundations, and
other projects.
Key Construction Points and Precautions
for Composite Geomembranes
Correct construction is crucial to ensuring
the anti-seepage effect of composite geomembranes:
- Base Layer Treatment: The
laying surface should be flat and firm. Remove all sharp objects such as
tree roots, turf, and sharp stones. Level with small-particle-sized sand
or clay.
- Laying and Overlap:
During laying, it should not be stretched too tight. The parts buried in
the soil at both ends should be corrugated to adapt to foundation
deformation. The edges of adjacent materials require sufficient overlap
width.
- Connection and Anchoring: When
connecting to surrounding structures (e.g., concrete), expansion bolts and steel plate pressure strips are often used for anchoring. Sealants like emulsified asphalt
should be applied at the connection points to prevent leakage.
- Protective Layer Covering:
After laying, promptly cover with a protective layer
(e.g., fine sand, clay, thickness not less than 30cm). Then, place block
stones or concrete prefabricated blocks on top as an erosion protection
layer. Avoid direct impact or heavy objects falling on the geomembrane
during construction.
- Welding Technology: For
large-area laying requiring splicing, thermal welding technology is
typically used for joining to ensure seam sealing.
How to Choose the Right Composite
Geomembrane?
Selection requires comprehensive
consideration of engineering requirements and product performance:
- Define Engineering Needs:
Determine the required material's mechanical indicators
(e.g., tensile strength, tear strength) and physical indicators
(e.g., membrane thickness, geotextile area weight) based on the
anti-seepage grade, withstandable water pressure, foundation conditions,
and presence of chemical corrosion.
- Refer to Design Standards:
Follow the requirements for material specifications, models, and execution
standards in the engineering design drawings.
- Common Specification Reference:
- One cloth one membrane:
Base cloth approximately 200-1000g/㎡, membrane
thickness 0.1-1.5mm.
- Two cloths one membrane:
Base cloth approximately 80-600g/㎡, membrane
thickness 0.2-1.5mm. A common example is 900g two cloths one membrane
(where the total weight of the geotextile is 400g, and the HDPE membrane
thickness is 0.5mm).
- Emphasize Material Quality:
Choose reputable manufacturers and pay attention to the material's durability, aging resistance, and uniformity.
Conclusion
Through clever material composition,
composite geomembranes integrate multiple functions such as seepage prevention,
drainage, reinforcement, and protection into one, providing an efficient and
reliable solution for modern civil engineering. With the advancement of
material technology and increasing engineering demands, the performance of
composite geomembranes will continue to optimize, and their application fields
will further expand, continuing to play an indispensable role in building safe,
green, and sustainable infrastructure for humanity.