Geosynthetic compositions and options for the minng working
Geosynthetic Compositions and Options for the Mining working
1 Geomembrane
Heap leaching projects, evaporation ponds, tailings, etc. in mining operations often experience very high loads and geomembranes are very commonly used. Geomembrane usage in heap leaching projects accounts for more than 40% of all geomembrane production. Geomembrane raw materials are high density polyethylene (HDPE), linear low density polyethylene (LLDPE geomembrane), low density polyethylene (LDPE geomembrane) \ polyvinyl chloride (PVC geomembrane), polypropylene (PP geomembrane) and EPDM Rubber (EPDM geomembrane). However, mining operations mainly choose HDPE geomembrane due to its high chemical resistance and physical properties. Thicknesses greater than or equal to 0.75 mm (30 mils), such as France and Germany, consider 1 mm (40 mils) polymer geomembranes. In addition to the characteristics of the geomembrane, other design issues must be considered, such as the effect of high stress, the type of foundation, and placement materials below and above the geomembrane.
Foundation conditions should be firm to minimize settlement over the life of the facility. Otherwise, the geomembrane will be stressed and overstretched, resulting in damage to the geomembrane. The subgrade surface shall provide a smooth, flat, firm, indomitable base for the geomembrane, with no sudden, sharp, or sudden changes or grade breaks that would tear or damage the geomembrane, and no loose rock fragments (>10 mm or 0.4 in.) )), sticks, sharp objects, or debris of any kind. If there are sharp objects, debris, or gravel, etc., a protective non-woven fabric is required to prevent the geomembrane from being pierced.
In the mining industry, there are no specific regulations for barrier applications, so lining thickness is usually chosen based on experience, expected ore loading, particle size of the material placed on top of the geomembrane, and material below. Due to the typical chemical resistance required for geomembranes, HDPE is used in most cases. HDPE is used in:
exposure to ultraviolet radiation
High chemical resistance required
Expected long-term useful life
High stress crackability is important (usually important for HDPE)
Good thermal oxidation resistance is required
Requires high puncture resistance
High mechanical properties are important.
Due to the expected service life of geomembranes (>>100 years), requirements for landfill base lining systems typically require a maximum deformation of 0.25%. In mining applications, shorter lifetimes may occur, so higher deflections (but less than 1.5%) may be acceptable. A key aspect in determining long-term performance is also the temperature of the liquid on the geomembrane.
2 Geosynthetic Clay Liner
Geosynthetic clay liners and multi-component clay geosynthetic barriers belong to the group of geosynthetic clay barriers, defined as follows:
Geosynthetic Clay Barrier: A factory-assembled structure of a geosynthetic material, in the form of sheets, in which the barrier function is performed by clay.
Geosynthetic Clay Liner (GCL): A factory-assembled geosynthetic barrier consisting of clay supported by a geotextile held together by needle punching, stitching, or chemical adhesives.
Multicomponent Clay Geosynthetic Barrier (MGCL): A clay or geosynthetic clay liner (GCL) with an attached asphalt, polymer, or metal barrier that reduces hydraulic conductivity or protects the clay core, or both Of.
GBR-C is used in mining applications such as heap leach facilities, evaporation ponds or tailings ponds, process solution containment, storm water containment, wastewater treatment ponds, closures and recycling.
Harsh environmental conditions challenge engineers designing such projects. In some applications, the lining system may require a composite lining system with a geomembrane or multi-component GCL. Due to the benefits that GCLs offer, they are increasingly seen as an alternative to compacted clay liners in mining applications, and in some cases MGCLs can replace geomembranes. Some of the benefits of GCL are:
Cost-effective padding and installation
Easy to install in most weather conditions
Effective barrier, especially under high normal loads
However, designers should consider site specific conditions (soil material)
3 Non-woven geotextiles
As a separator, geotextiles are used to prevent adjacent soil layers or fill materials from mixing with each other. In filtration applications, nonwoven geotextiles are used to retain soil particles while allowing liquids to pass through the filter media.
Needle-punched (mechanically bonded) nonwovens are robust geotextiles capable of withstanding harsh installation conditions and challenging construction loads. Their unique flexibility and elongation properties combine to provide high puncture resistance without sacrificing filtration performance. When properly selected, needle punched nonwovens can provide excellent long-term filtration and achieve high interfacial friction angles.
In mining applications, geotextiles are widely used to protect geomembrane barriers from puncture and unacceptable deformation.
4 Geosynthetic drainage synstem
4 Geosynthetic drainage system
Drainage in heap leach mats is important for metal recovery, stability and spill control. Regardless of the type of drainage material chosen (aggregate or geosynthetic), the liquid drainage layer at the bottom of the heap leach pad should meet the following requirements:
The liquid should be able to flow into the drainage layer without creating a head in the heap leach pad
Sufficient long-term water permeability in the drainage layer with as low a gradient as possible on the lining system
Durable system for drainage of heap leach pad life (chemical compatibility)
Withstand compressive loads (long term and short term)
Meets shear stability requirements
Avoid damaging the lining system
While most heap leach mats are covered with aggregate as drainage material (usually over 0.5m of crushed gravel (10mm to 50mm)), geosynthetic drainage layers are now increasingly used as an alternative to traditional gravel drainage systems Taste.
Geosynthetic drainage systems are defined as: A three-dimensional prefabricated product made of synthetic raw materials, consisting of a drainage layer (core), covered in most cases with at least one geotextile filter for liquid and/or or steam delivery.
A further application of geosynthetic drainage systems is as a leachate detection system between two barrier liners, such as between two polymeric geosynthetic barriers.
In order for a geosynthetic drainage system to be equivalent to a mineral drainage layer such as a heap leach pad or to surpass it, performance testing must be sufficient to demonstrate its long-term performance. These should include filtration performance of geotextile filters, long-term compressive performance of geosynthetic drainage systems under field loading, long-term levels (in-plane flow/permeability), and other site-specific requirements such as interfacial shear behavior or puncture resistance .
During the evaluation and selection process, the design engineer will often choose between a mineral drainage layer and a geosynthetic drainage system. Engineers are more familiar with mineral materials and oversee the potential of geosynthetic drainage systems. However, what disadvantages may arise from the use of mineral drainage layers are often monitored. Placing this type of material directly on the geomembrane can cause puncture stress and may have damaged the geomembrane during placement. Fur stress can occur during the loading of heap leaching pads, especially when no or insufficient protective layer is used. The placement of the drain seams is also time-consuming and slows down the overall mining operation. On the other hand, geosynthetic drainage systems have many advantages. Ease of installation, especially on slopes, consistent material properties, faster installation, puncture-resistant and drainage layers combine to save costs in many cases.
Other benefits of using a geosynthetic drainage system are:
High volume flow path for fluids
Generally lower installation and material costs, thus a cost-effective alternative to mineral drainage materials
Easy and quick installation due to light weight
5 Reinforced geogrid
In mining, geogrid applications include base reinforcement and stabilization, slope and retaining wall reinforcement, and tailings pond overburden reinforcement. In situations where the bearing capacity of the soil is insufficient or the shear properties are too low to stabilize under planned slope inclinations or loads, geogrid reinforcement helps bridge gaps for adequate stability and safety.
The geogrid structure should provide rigid holes. This affects the lateral confinement ability of aggregates interlocking in the pores. The greater the pore size stability of the geogrid, the better lateral restraint it provides for the granular material. The interaction with aggregate is one of the main principles of geogrid reinforcement. Thanks to the interlocking mechanism, the geogrid absorbs stress from the soil and increases safety and serviceability.
In order to absorb stress optimally, geogrids need to provide high strength at low strains. The greater the tensile modulus at low strain, the lower the strain and ultimate deformation developed in the structure. Ultimate tensile strength affects the level of tensile strength available at low strain, and an increase in ultimate strength results in the same rate of increase at low strain.
In structures that utilize geogrids to provide adequate stability and safety as determined by structural analysis, the long-term performance of the product becomes decisive. Different raw materials and manufacturing processes affect properties such as creep behavior, robustness to installation damage, and chemical/biological effects. These values directly affect the long-term design strength of the product considered in the stability analysis. Products with the same ultimate strength often differ in the long-term design strength they result in.
