- What are geomembranes and where are they used?
Geomembranes are a class of impermeable geotextiles used in a wide range of applications, including waste management, hydraulic, transportation, oil and gas applications, mining, and in the construction of surface water features. Reinforced polyethylene (RPE) is a composite product consisting of one or more reinforcing scrim layers of woven polyethylene geotextile (usually HDPE), sandwiched between layers of an impermeable geomembrane such as LDPE.
- What is the purpose of a geomembrane?
Geomembranes are sheets of impermeable polymeric compounds that are used to control and prevent the movement of water from one place to another. They’re useful in stabilizing earth, preventing erosion, and containing waste in landfills. When reinforced as a composite geomembrane, they’re particularly useful in containing toxic materials since they’re highly resistant to both chemical and environmental degradation and are effective at preventing the movement of water from the containment area into the environment.
- What are the different properties of a geomembrane?
When used to compare one geomembrane product to another, there are several measurable properties. When selecting the best product for your application, it’s useful to compare properties that will be important to that specific use. These properties (and how they change over time) can also be used to evaluate the general condition of an installed geomembrane and possibly determine if repairs will be reliable or if complete replacement is necessary at the end of its serviceable life.
The main physical properties of primary (unaltered) geomembranes include:
Thickness and texture
Density
Melt flow
Weight
Vapor transmission
The main mechanical properties include:
Tensile strength and elongation
Tear resistance
Impact resistance
Puncture resistance
Interface shear strength
Anchorage strength
Stress cracking
The main endurance properties include:
Ultraviolet light exposure
Radioactive degradation
Biological degradation
Chemical degradation
Thermal behavior
Oxidative degradation
- What are the advantages of a textured geomembrane?
Geomembranes are usually available with smooth or textured surfaces, and both have distinct advantages, depending on your needs. Originally, all geomembranes were smooth, and that’s valuable in some cases because it allows the product to slide over surfaces easily, permitting smooth, undisturbed water flow, and discouraging algae or other materials from adhering to the liner. Smooth geomembranes are preferable (or required) for applications such as base layers in landfills, tailings storage facilities, and in the construction of artificial lakes, reservoirs, and other bodies of water, including wastewater ponds.
In contrast, liners with textured surfaces allow adjacent materials to get a better grip on the liner, impeding shifting and other movement. This means that the interface with soil, clay, textiles, and other materials is stronger. The coarseness of the texturing (asperity) can be adjusted during manufacture and is measured by calculating the distance from the core of the membrane to the top of the texture peak.
While textured membranes have several good advantages, it’s important to realize that the addition of any sort of texture will affect the physical properties of the geomembrane, including tear and puncture resistance, but the difference is most dramatic in changes to its tensile strength. In any application where texture is desired, it’s important to weigh the degree of texturing (asperity) against the loss of tensile strength and other factors.
- Why are thick, specialized liners necessary in landfills?
Since it’s impossible to 100% control the materials that are transported in, municipal landfills inevitably contain a wide variety of dangerous waste, including acids, pesticides and biological waste that may carry harmful microorganisms, toxic metals, and even small amounts of radioactive material.
When water passes through individual cells in the landfill, it inevitably picks up whatever toxins and contaminants are available. Left to flow through multiple layers of landfill, fresh rainfall becomes a highly contaminated, toxic waste which will eventually reach and infiltrate the local water table.
Landfills use impermeable covers to prevent water from entering the landfill cells, and liners are used to separate the cells, preventing any accumulated moisture from flowing down through the stacks and out into the environment. These liners are thick because they must be strong, durable, and largely immune to punctures. Composite geomembrane (RPE) liners, however, are lighter, thinner, and more flexible than other options and offer specialized performance advantages like robust chemical resistance, tolerance of temperature extremes, and longevity.
- What is the best liner for a landfill?
Landfill liners should be impermeable, durable, affordable, long-lasting, easy to install, and resistant to degradation from chemicals. Composite geomembrane liners such as RPE can meet and exceed these exacting demands, offering the best balance between performance and budget-friendliness.
RPE (reinforced polyethylene) liners are composite liners, formed by sandwiching a woven layer of HDPE geotextile between two layers of impermeable LDPE geomembrane. When the layers are joined together, the composite material takes on the best characteristics of each component (strength, flexibility, chemical resistance), and counters the less favorable ones.
HDPE has been generally accepted as the preferred material for use in municipal solid waste and secure landfills due to its strength and chemical resistance. RPE, however, offers the same level of performance but is also easier to install and more impermeable than HDPE alone.
- Is geomembrane waterproof?
Geomembranes, as a class, are manufactured to be impermeable to most liquids and are typically employed to prevent the infiltration of toxins and other contaminants into the soil. Geomembranes are also used as a waterproof barrier in containment tasks like reservoirs, waste treatment plants, evaporation ponds, and golf courses.
- What is a geomembrane liner?
A geomembrane is a synthetic material made from thin, continuous polymeric sheets. Liners constructed from a geomembrane are highly impervious to water and most other liquids, making them excellent options for controlling the movement of liquid as well as secure containment of hazardous materials.
Geomembranes are available in a highly customizable range of properties, including physical, mechanical, and chemical resistance, textures, colors, thickness, flexibility, and more. This wide range of options means that the material used for any given project can be optimized to provide the highest quality performance for those specific parameters.
- What is the function of geocomposites?
Geocomposites are materials formed by joining together two dissimilar materials in order to create a new material that combines the strengths of each component, while eliminating the weaknesses. Geocomposites can be permeable, and are often used in road construction, where they maintain separation between soil layers, filter and control drainage, and provide reinforcement, such as increasing the stability of underlying soil
Impermeable geocomposites, on the other hand, are essentially waterproof, and are used to contain or control the movement of water and other liquids in a variety of situations. Reinforced polyethylene (RPE) is a popular example, valued for its strength, durability, resistance to a range of chemical and environmental degradation, and affordability. RPE is formed by sandwiching layers of a woven reinforcement material such as HDPE between layers of an impermeable geomembrane such as LDPE.
Composite geomembranes such as RPE are used for a huge range of applications, ranging from backyard fishponds to wastewater treatment plants to secure storage of toxic mining waste in tailings ponds.
- What are typical composite geomembrane features and properties?
Composite geomembranes can be manufactured from a variety of materials, so the specific properties of any given combination will vary. However, it’s safe to say that many similar qualities are targeted. When you’re selecting from a variety of similar options, keep in mind the most important qualities for your specific application and weigh the candidates based on their individual performance in those areas.
Here are some commonly sought-after properties in composite geomembranes:
- Excellent impermeability to liquids, especially water
- Durability, especially resistance to punctures and tears
- Options for textured or smooth surfaces
- Continued flexibility and resistance to damage from extreme cold
- Resistant to degradation from elevated temperatures and environmental exposure
- High strength, good elongation (ability to stretch), and the ability to maintain its shape even under high stress.
- High resistance to chemical damage, including acids, alkali, and corrosive materials.
- NSF/ANSI 61 certification for potable water applications
