|International web site Geosynthetics Drainage DRAINAGE OF LANDFILL|
Drainage of landfill
Ground and wall drainage
Geonets and geocomposites are now used in a wide range of applications on controlled landfills, providing mechanical protection to geomembranes, gas drainage, collection and drainage of leachate and other liquids in the ground, as well as a barrier against capillary action.
Drainage systems for leachate collection and removal serve to limit the hydraulic head within the drainage layer.
The use of geocomposites to capture and gather leachate or other liquids entails both technical and practical benefits, in comparison to granular materials (aggregate) they are readily available and easy to install, they confer major stability to the slopes they are laid on, and exhibit considerable chemical resistance and excellent erosion/ corrosion resistance.
Synthetic geocomposites also provide real economic advantages if we compare their purchase price and installation costs to those of a traditional drainage system made up of layers of sand and gravel.
The minimal thickness of the geosynthetic layers and the possibility of building landfills with steeper slopes also allow to increase landfill capacity as more usable volume is available for waste storage.
The estimate of average cost savings is approximately 50% when using a synthetic product instead of a traditional one.
Municipal Solid Waste Landfill
Collection and removal of leachate in landfills
TENAX Drainage systems
Capping and remediation of contaminated sites
The TENAX drainage geocomposites in the landfill cover system limit the infiltration of water inside the landfill. This eliminates the possibility of water flowing over the membrane, reducing the soil/membrane friction coefficient to practically zero which in turn would cause sliding of the cover soil over the waterproofing cover layer.
Installation of the Geocomposite for biogas drainage
Installation of the Geosynthetic Clay Liner or Geomembrane
Installation of the Geocomposite for drainage of infiltrating rain water
Laying of the "gripping" and reinforced 3D Geomat
Anchorage of the complete covering system in anchor trenches
Spreading of the upper layer of vegetative soil cover
Completed with hydroseeding or normal seeding
Collection and disposal of surface water
If percolating water is not appropriately drained and water is allowed to flow through the cover soil it will gather on top of the impermeable liner causing dangerous conditions.
The extremely high hydraulic head caused by inadequate drainage can bring about catastrophic cover soil failure; in fact, numerous failures in landfills triggered by infiltration have been recorded and analysed.
TENAX drainage geocomposites that are correctly
designed and installed on top of the impermeable layers,
provide a guaranteed method for disposal of the total
amount of precipitation that would filter through the
vegetative soil cover.
The stability of the cover soil can be considerably reduced by pressures
produced by biogas built-up beneath the capping layers (geomembranes
or GCL’s) until failure occurs.
According to recent research on the transmission rate of gas and based
on the theory of intrinsic permeability, the transmissivity of LFG (landfill
gas) results to be ten times lower than the hydraulic transmissivity ratio
in any porous medium.
This means that, to drain biogas, drainage layers with a high hydraulic capacity are required.
Surface erosion control and cover soil stabilisation
One of the major problems that arise during the design and construction of a permanent landfill covering system (capping) is how to keep a sufficiently thick layer of topsoil on slopes to permit the creation of lasting vegetative growth.
As a matter of fact, the angle of friction at the interface between the impermeable layer and the vegetative cover soil has usually very low values, insufficient to prevent the sliding of topsoil, even on shallow slopes.
The problem is furthermore enhanced by the need to carry out checks that prove compliance to the new technical regulations for landfill construction.
The use of a suitable geosynthetic material is therefore essential to convey to the covering soil the properties required to confer stability.
TENAX MULTIMAT R reinforced geomats allow the retention of vegetative material to a significant depth due to their three-dimensional structure and “gripping effect”, even on very steep slopes; after placing the mats immediately above the waterproofing layer (or, in case, on top of a geocomposite with filter- drainage functions for meteoric water) and firmly anchoring them at the top (in anchor trenches or by re-filling with appropriate material) and pegging into place on the slopes (using apposite large-head pegs), TENAX MULTIMAT R is successively “filled” with an abundant amount of slightly compacted vegetative soil.
Another way of “capping”, consists of the use of TENAX TENWEB geocells that allow the containment and stabilisation of vegetative soil into depths ranging from 7.5 to 10 cm, according to the type of geocell adopted, with the possibility of overlapping the geocells in several layers.
For the permanent capping of controlled waste landfills and the remediation of contaminated sites, TENAX has developed, in addition to its well established range of TENAX TENDRAIN and TNT geocomposites providing filter/drainage protection, a new range of TENAX HF High Friction and TENAX HD High Drainage Geocomposites:
Landfill in Cerro Maggiore, Italy
Containment of expanded clay
La Glacier Veolia landfill (France):
CONFINEMENT BARRIERS AND EMBANKMENTS
To increase the usable volume of a landfill two types of action can be taken basically: the construction of reinforced embankments acting as confinement barriers or retaining walls at the base, and the insertion of geosynthetics directly inside the waste mass, thus building an embankment of reinforced solid urban waste.
Confinement barrier and raised
Confinement barriers in landfill and reinforcement for municipal waste disposal sites
The construction of Reinforced Soil Embankments with TENAX mono oriented geogrids provides extremely reduced cross sections in comparison to the non-reinforced ones, an increase in usable volume for waste disposal and, consequently, a reduction in the amount of land required for the construction of embankments.
This technology is now commonly adopted, as it does not present any particular problems from the point of view of design: the calculation models are standard for reinforced embankments while waste volumes are merely involved as a thrusting force behind the structure.
By applying the technology for Reinforced Soil Embankments directly on Municipal Waste Disposal sites, the usable volume available for waste disposal would be even more, with lower construction costs.
The TENAX RIVEL integrated System for reinforced embankments features the use of TENAX mono-oriented integral HDPE geogrids as reinforcing elements.
Thanks to the TENAX RIVEL System it has become possible to build extremely resistant reinforced embankments that can be constructed as edge embankments of minimum overall dimensions, providing an increase in landfill capacity volumes.
The TENAX RIVEL structures are designed to withstand both static load stress caused by the mass of waste as well as potential seismic accelerations for the area.
NENT, Hong Kong
Landfill perimeter confinement
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