With so many uses for geomembranes in the mining industry, during both active and closed stages of a project, it’s no wonder they’re so widely used. However, not all geomembrane products will work for mining applications. Using the wrong material for a hydraulic fracturing brine pond or a heap leaching pad will only result in failures and costly losses. Making the right choice from the start is easier than you might think. Simply choose a polymer based on their characteristics, decide on reinforced and textured features, and consider how you plan to install the liner.
Choosing a Polymer
There are over a dozen different common polymers used for manufacturing geomembranes. These products are further divided into dozens more specific formulations of additives and plasticizers. Start with a general polymer category and then narrow down the options based on product specifications. The materials commonly used for mining geomembranes include:
- High density polyethylene (HDPE). This durable material is widely available, but it’s far more prone to cracking under stress than other types of polyethylene. It offers decent chemical resistance and less UV resistance than RPE. Welds are reasonably strong for reliable seams. Unfortunately, this is balanced out by poor puncture resistance and extensive thermal expansion in applications with hot wastewater. This material isn’t a great choice for use on its own in a mining project.
- Polyvinyl chloride (PVC). More flexible than HDPE liners, PVC isn’t very durable and lacks the chemical resistance necessary for mining use. The material resists wrinkling relatively well due to its flexibility, but it’s less durable and offers poor tear resistance in rocky soils. It’s also not entirely UV resistant in most formulations and will break down eventually when installed in an exposed setting. High and low temperatures also damage PVC liners, both of which are possible on the mining site. Skip this material for process and storage ponds.
- Chlorosulfonated polyethylene (CSPE). Based on the popular polyethylene polymer, this particular formulation is strongly resistant to certain chemicals like bleach. Few of its particular strengths are needed by the mining industry. With a low tensile strength, it’s a particularly poor choice for heap leach pads and similar high weight applications. The stretching force of sediment or ore will cause too many tears and punctures to develop in a CSPE liner. Unless the specific chemical resistance is needed from this liner, avoid it for most mining geomembrane purposes.
- Flexible polypropylene (FPP). Polypropylene is generally used in rigid forms, but it’s also available as a flexible liner material. Unfortunately, its weakness against hydrocarbons mixed into the mining waste makes it a bad choice for most natural gas, petroleum, and hydraulic fracturing purposes. It’s easy to manufacture in large sizes, but it’s harder to find in general and tends to cost more per square foot than other commonly available liner materials. It’s generally not a good fit for most mining geomembrane specifications.
- Low density polyethylene (LDPE). For the combination of chemical resistance and flexibility, LDPE is a relatively good choice. Yet it still has some disadvantages that keep it from being the ideal choice for most mining projects. First, this material is even less UV resistant than HDPE geomembrane. It’s also less chemical resistant. While the softer material is less likely to wrinkle than stiffer membranes, especially when reinforced, it’s not as durable as you need for mining purposes. Rough ores and sediments will quickly wear out a liner made of LDPE alone. LDPE is not an ideal liner when used alone, but it may work well in combination with other geomembranes.
- Reinforced polyethylene (RPE). For the best features of all the above polymers in a single package, look for RPE geomembranes. These mining geomembranes offer the highest grade of both chemical and UV resistance due to the combination of both HDPE and LDPE in a single product. The reinforced design provides strength, wrinkle resistance, conformation to unusual curves, and tear resistance all at once. RPE also works well for covering both active and closed mines. If you’re in search of an RPE geomembrane product that can handle the challenges of mining installations, check out our selection at BTL Liners.
Benefits of Reinforced Geomembranes
Reinforced geomembranes are recommended for the mining industry. These liners offer a better lay flat experience, reducing the number of wrinkles formed during installation. Wrinkles that aren’t removed, slowly compress over time due to the weight of the water and combined sediment. Ores being processed in ponds are especially heavy and tend to stretch non-reinforced liner products. Reinforced polyethylene (RPE), in particular, is designed to resist stretching and expansion under heavy loads. These liners are also more resistant to freezing damage caused in cold climates, making them a good choice for mines located in the higher and lower latitudes of the world.
Surface Texture and Why It Matters
The surface texture of a particular geomembrane product also determines how well it will bond with the soil above and below it. Smooth membranes may spread easily, but they don’t offer as much grip as products with some kind of texture on the surface. Interfaces that create more friction help prevent movement of the liner, especially when using steeper slopes around the sides of the pond or catchment basin. Textured liners also help control erosion by slowing the flow of water over the surface when there’s a runoff issue. If you’re installing any exposed liners, you’ll definitely want a textured product to keep surrounding material from shifting onto the surface.
Weight, Durability, and Stiffness
Consider how weight, stiffness, and durability work together to control the functionality of a particular mining geomembrane. Thicker geomembranes tend to be more durable, but they’re also generally stiffer and heavier as well. Stiff liners are at greater risk for cracking, especially when wrinkled. It’s also harder to get the material to fit smoothly into corners and form good seams in uneven areas. Thinner materials are less stiff and therefore more flexible, in addition to offering a lower weight. Low weight materials are easier to install, as are flexible products. If you choose a material like RPE that is durable and strong despite being thin and flexible, you can enjoy the best of all three factors in one package.
Features Essential for Mining Use
Geomembranes need more than just flexibility and chemical resistance to qualify for mining use. Ease of installation and seam sealing determines a large proportion of the total cost. If you choose a less flexible and heavier material that is hard to spread out and seal together, it’ll cost more in the long run than an easier to handle material. Make sure you’re choosing a vapor blocking barrier as well if that’s specified in the project plans. Don’t forget about wear and tear resistance if you plan to use any heavy equipment to scrape or empty the processing ponds of valuable sediments and ores at the end of the treatment cycle.
Exposed vs Buried Installation
Only geomembranes explicitly labeled for exposed use should be installed that way. Using liners designed for buried and covered installation in an exposed setting will only lead to rapid failure. UV exposure is detrimental to liners that aren’t designed to withstand it on a daily basis. Even short-term exposure to a buried liner due to shifting ballast can lead to leaks. Check on ballast regularly to keep low spots well covered so UV damage can’t occur.
Don’t become overwhelmed by the options available today for mining geomembranes. If you need help making your selections for various parts of your project, contact us here at BTL Liners. Our team will advise you on product choices based on each section of treatment or processing steps. No matter what kind of ponds and channels you need for your mine, we can help you find the right liner.
