TenCate Mirafi® high strength geotextiles on Extremely Soft Soils
Soft site impoundments can be very soft and may cover a large area, making the closure difficult to construct. The soft site impoundments can also be below or above water level. Despite the complexities, capping of soft site closures are possible with medium to high strength TenCate Mirafi® Woven Geotextiles which have the functions of separation, filtration and reinforcement within one geotextile. TenCate Mirafi® woven geotextiles can be fabricated in the factory or on-site into large panels with high seam efficiencies to facilitate site installation and minimize geotextile wastage.
TenCate Mirafi® high strength geotextiles can be laid directly on the tailings or sludge to increase the shear strength of the fill material and see an increase in foundation bearing capacity. This enables rapid site access and construction, ordinarily only achieved through high volumes of imported soil, left to consolidate over an extended period.
TenCate Mirafi® high strength geotextile both separates introduced material and provides a reinforcement function, so understanding the soil parameters and installation method onsite is critical to correct geotextile selection. For critical tailings applications design must consider the Polymer utilised to manufacture the product, which will see loss of tensile performance if incompatible to site chemistry. The Geofabrics GRID and Technical Hub are well versed to support with this expertise.
Tensar Geogrid Mechanical Stabilisation
The Tensar TriAx® is the most advanced geogrid in today’s market and the result of 30 years continual innovation and development in designing superior Roads, Embankments and Working Platforms . The key Tensar design principle is to mechanically stabilise soils available for capping construction, which results in a positive shear response through the capping depth and a structurally superior formation for construction traffic. To achieve maximum benefit, the choice of Geogrid must be designed link to the construction process and load conditions. The net result is a site-specific cost saving by implementing a thinner soil layer that achieves increased bearing capacity and stability under load.
GEOWEB Mechanical Stabilisation
A Geoweb Cellular Confinement System can be laid above a bidim geotextile on the tailings surface, to provide a thin soil layer that provides maximum bearing capacity for construction traffic. The structure distributes surface stresses extremely effectively to prevent soil shear failures, whilst also allowing a thin pavement construction to maximise soil performance under construction loads.
Wick Drains for stability
Wick drains are designed to speed up the consolidation of compressible soils by providing shorter flow paths for water contained in the soil. As the soil consolidates its strength improves which will allow higher loading from larger stockpiles. The use of wick drains can reduce consolidation times from years to months.
Capping Liner - Geosynthetic Clay Liners
Elcoseal® Geosynthetic Clay Liners (GCLs) are hydraulic barriers that consist of a thin layer of high quality bentonite sandwiched between two or more Geotextiles. These present both as single liners and composite liners in conjunction with Geomembranes to cap tailings dams, pits and other waste storages. The challenge is the vast differences between world bentonite sources that need to be designed to ensure compatibility with the site chemistry, and Geotextile types that link to mechanical performance.
The design must answer key questions to determine suitability of a range of GCL types, to ensure the environmental conditions do not cause detriment to the bentonite, and that internal and external shear properties are suitable to survive long term capping settlements. Geofabrics has a range of options that link to interface shear testing and ten years worth of hydraulic testing on a range of liquors at the GRID laboratory to support your design.
Capping Liner – Polymeric Geomembranes
Geofabrics has access to premium Geomembranes sourced from around the world. From commonly specified Polyethylene (HDPE and LLDPE) Geomembranes to select polymer liners to meet specific waste chemistry from Cooley Group. Solutions must be designed specifically to the chemistry of the liquor to be detained, meet the project stress conditions and ensure that atmospheric exposure (UV, Temperature) does not compromise the liner design life. The Geofabrics GRID Laboratory has the testing capability to establish specific site liner criteria and has a decade worth of data in this field.
Teranap's bituminous geomembranes (BGMs) are a reliable waterproofing system engineered to suit challenging site conditions that compromise other liner options. Teranap has unique mechanical properties that have high robustness to survive challenging subgrades and cover soils, and overcome site conditions that would be detrimental to other liners.
Teranap uses a modified form of bitumen with a high level of chemical resistance and useable temperature range, while keeping its natural waterproofing qualities. The Geofabrics GRID laboratory can analyse damage factors, chemical compatibility and friction properties to ensure the BGM is compatible to your site.
A Drainage Geocomposite can be used to drain stormwater away from above the lining system or capture and relieve porewater or gas below the lining system. The choice of Geonet will depend on the load condition and flow volume required. The Geofabrics GRID Laboratory has a designated Transmissivity Test rig to test Geonets under project stresses. In conjunction with this, a Geotextile can be designed and tested to establish maximum flow and solids retention to ensure that the Geonet system does not clog or become unstable.
Protection and Filter Geotextiles - Geofabrics bidim® or Texcel®
A Geotextile is used to either serve a protection function for the Geomembrane Lining system, or serve a critical filter function when placed over the drainage aggregate or Geonet in capping applications.
The selection of the Geotextile begins with choosing the polymer that meets your site chemistry, primarily Polyester or Polypropylene. PET and PP sources however, are varied in terms of their additive packages, so for applications of extreme pH or extended UV exposure it is critical that the right product is established through direct testing at the Geofabrics GRID laboratory.
Protection or Cushion Geotextiles: In terms of Cushion Geotextile function, the bidim nonwoven geotextiles have a three-dimensional structure that provides maximum protection function per mass, so will always be the first choice for Geomembrane protection to maximise costs. The Texcel Range of Staple Fibre Geotextiles made from either Polyester or Polypropylene are designed for specific polymer, exposure or stress conditions. The critical design criteria can be established through the Geofabrics GRID Laboratory, that has a decade of analysing Protection Geotextiles over Geomembranes to demonstrate technical performance and maximise bang for buck for the Geotextile selected.
Geotextile Filters: Geotextile Filters are critical to maximise drainage performance, and the correct type can provide numerous benefits to waste and tailings dams. The design aim is to choose a Geotextile that has the right structure and pore size to maximise both water through flow and solids retention. A well-designed filter geotextile prevents clogging of drainage aggregate or more critical Geonets, increases dam capacity by removing increased water and improves tailings stability. It also allows maximum recovery of dam water for re-use onsite which is becoming a critical part of the mines Social Licence obligations.
The choice of Geotextile will begin with polymer compatibility and can be subjected to desktop filter design. The key cost saving opportunity is presented by the Geofabrics GRID Laboratory which has 10 years of testing and data with mine sludges, to achieve maximum filter and subsequent drainage performance.
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