RE: Liner questions
I am designing a surface impoundment with interior side slopes of 1.5H:1V. This impoundment requires (per regulations) a geosynthetic clay liner (Bentomat DN or equivalent), 40-mil HDPE secondary liner, and 60-mil HDPE primary liner. A leak-detection system has been requested.
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The pit is small (approximately 500ft x 200ft) without much travel distance for fluids should a leak occur. To avoid too many liners on a steep slope, I would like to use two textured HDPE liners as both the primary and the secondary without adding a fourth layer in for the leak-detection system.
I have the following questions:
(Melissa | Missouri)
Reply: Tough questions … 34 degrees is at, or slightly higher than, the best of geosynthetic interfaces (e.g., nonwoven to textured, internal to GCLs, etc.). So you are flirting with disaster to begin with.
It is much worse with a GM-to-GM even when they are textured. In fact, even more so, since the shear plane must ride up on the asperities. What remaining transmissivity there is depends on the normal pressure applied.
Clearly ASTM D is the appropriate test to use and will also allow one to get a glimpse of how the asperities behave.
Lastly, it very much depends on how the texturing has been manufactured. I suspect that blown film will indeed be different from structured with regard to shear strength and transmissivity.
Melissa, you need to do some lab testing to quantify my commentary.
Geosynthetic clay liner and geomembrane are geosynthetic materials used in a variety of engineering and environmental applications. Although they have some similar anti-seepage properties. But they have obvious differences in composition, performance and application.
BPM Geosynthetics is the leading geosynthetic clay liner and geomembrane manufacturer and supplier with 13+ years of Geosynthetic clay liner and HDPE geomembrane manufacturing experinces. In this article, we will discuss the differences of geosynthetic clay liners vs geomembranes. By comparing the differences between the two, we can make a better choice between a geosynthetic clay liner (GCL) and a geomembrane for your specific project.
Geosynthetic clay liner (GCL), also known as clay blanket, bentonite blankets, bentonite mats, prefabricated bentonite clay blankets and clay geosynthetic barriers, are factory-made hydraulic barriers consisting of a layer of bentonite or other composed of a very low permeability material supported by geotextiles and/or geomembranes that are mechanically fastened together by needling, stitching, or chemical adhesives. GCL liner is widely used in landfills to trap internal leakage. Its bentonite, consisting primarily (>70%) of montmorillonite or other expanded clays, is the preferred and most commonly used GCL. A typical GCL structure consists of two layers of geosynthetic material sewn together and surrounded by a layer of natural or processed Sodium bentonite. Typically, woven and/or nonwoven textile geosynthetics are used, however, polyethylene or geomembrane layers or geogrid geotextile materials have also been incorporated into the design or replaced the textile layer for added strength.
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BPM geosynthetic clay liners are geosynthetic material specially used to prevent leakage in artificial lakes and waterscapes, landfills, underground garages, rooftop gardens, pools, oil depots and chemical storage yards. It is made of high-expansion Stable sodium bentonite is filled between a special composite geotextile and a non-woven fabric. The bentonite anti-seepage mat made by acupuncture can form many small fiber spaces. However, the bentonite particles cannot flow in one direction and will flow in one direction when exposed to water. A uniform and high-density gel-like waterproof layer is formed inside the pad to effectively prevent water leakage.
A geomembrane is an extremely low-permeability synthetic membrane liner or barrier that can be used with any geotechnical-related material to control fluid (liquid or gas) migration in man-made projects, structures or systems. Geomembranes are made from relatively thin, continuous polymer sheets, but they can also be made by impregnating geotextiles with asphalt, elastomers or polymer sprays, or as multi-layer asphalt geocomposites. Continuous polymer sheet geomembranes are by far the most common.
BPM Geosynthetics geomembrane is a waterproof barrier material produced from high-density polyethylene resin. The full name is “high-density polyethylene film”, which has excellent environmental stress cracking resistance, low temperature resistance, aging resistance, corrosion resistance, a large operating temperature range (-60–+60) and a long service life. It is widely used in domestic waste landfill anti-seepage, solid waste landfill anti-seepage, sewage treatment plant anti-seepage, artificial lake anti-seepage, tailings treatment and other anti-seepage projects.
Geosynthetic Clay Liner consists of a layer of bentonite encapsulated between two geotextiles or geocomposites. Bentonite is a natural clay with excellent swelling properties that provides high levels of water conductivity and chemical resistance.
Geomembranes are synthetic materials made from flexible polymer sheets. They are typically made from materials such as high-density polyethylene (HDPE), low-density polyethylene (LDPE), polypropylene (PP) or polyvinyl chloride (PVC). BPM Geosynthetics geomembranes offer excellent impermeability and chemical resistance.
GCL waterproof blanket, Sodium Bentonite Geosynthetic Clay Line, is a new type of waterproof material. It is made of natural sodium bentonite, wrapped with two layers of geotextile, and reinforced with needle punching. Its anti-leakage mechanism is: the sodium-based particle bentonite selected for the bentonite waterproof blanket can expand more than 24 times when exposed to water, forming a uniform colloid system with high viscosity and low filter loss. Under the restriction of two layers of geotextile , causing the bentonite to expand from disorder to order. The result of continuous water absorption and expansion is to make the bentonite layer itself dense, thus having a waterproof effect. In order to facilitate construction and transportation, bentonite is locked between two layers of geosynthetic materials to protect and reinforce, giving the GCL waterproof blanket a certain overall tensile and puncture strength. GCL is primarily used as a barrier to prevent fluid migration in applications such as landfill covers, safety basins, and other hydraulic barriers. The bentonite in GCL swells on contact with water, creating a low-permeability barrier.
HDPE Geomembrane uses the impermeability of plastic films to block leakage channels in earth dams. It uses its large tensile strength and elongation to withstand water pressure and adapt to dam deformation. It aims to provide a highly impermeable barrier to prevent fluids ( including liquids and gases) migration. They are commonly used in applications such as landfill liners, ponds, reservoirs, mining facilities and other containment systems.
Geosynthetic Clay Liner (GCL) GCLs exhibit relatively low permeability due to the swelling properties of bentonite clay. The bentonite clay particles create a tortuous path for fluid flow, reducing hydraulic conductivity.
HDPE Geomembranes have very low permeability, providing an excellent barrier against fluid migration. They are engineered to have consistent and predictable permeability characteristics.
Geosynthetic clay liner is typically installed by unrolling them onto the prepared subgrade. The seams between adjacent GCL panels are often overlapped and mechanically or chemically bonded.
Geomembranes are installed by unrolling the sheets over the prepared subgrade and then seaming them together using various techniques such as heat welding, adhesive bonding, or fusion.
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