General
General Informations
Geosynthetics are used for separation, filtering and reinforcement and have an important role to play wherever different soil layers come into contact, where water may be present, and where the applied loads cannot be absorbed and transferred by the soil alone.
This means that geotextiles are used across the entire spectrum of general and specialist earthworks, to ensure stability and to extend the useful life of structures.
More than 40 years of experience in the use of geotextiles in earthworks are reflected in the successful implementation of innovative geotechnical solutions. A comprehensive body of regulations and standards is available, which make this expertise available to everyone and provides quality assurance in both the manufacture and use of geosynthetic products.
The TELEVEV range of geotextiles perfectly fits this description. The technology used for manufacturing the material has been in continuous development over the last 20 years and this, together with the use of high-modulus polyester multi-filaments, has resulted in the current range of products, all of which are optimally suited to earthwork applications.
Due to the high tensile strength and low elongation properties of polyester, it has long been recognised as the ideal choice for achieving optimal reinforcement in combination with the shear deformation of the soil. This also applies to the long-term behaviour of the geotextile under permanent loading.
Furthermore, TELEVEV woven geotextiles are so robust that the material can be laid and the soil layers above it compacted using the heavy machinery that is normally present on the construction site.
Due to their excellent chemical resistance, which ensures good resistance to weathering, and their resistance to microbiological degradation, TELEVEV woven geotextiles are suitable for complex permanent structures.
TELEVEV is a brand name product of the renowned manufacturer of geosynthetic reinforcement and erosion control products,
TELE TEXTILES AS of Norway, whom we represent as the company’s exclusive sales agent in Germany.
Function
Functionality of TELEVEV woven polyester fabrics
Separation
Separating two soils of different grain structure where they come into contact helps significantly to ensure that the desired properties of the high-quality fill material are maintained in the long term. The separating function alone ensures that fine-grain and coarse-grain layers are prevented from mixing. This ensures that the mechanical properties are preserved and that the water permeability remains practically constant.
Filtration
On detailed examination, further hydraulic phenomena must be taken into account in the case of flowing water, varying water levels or the drainage of surface water. A filter material with long-term effectiveness can be used to prevent the fine grains from washing into the coarse-grain layer, for example. This ensures positional stability of the soil layers and prevents the changes in volume that could otherwise occur as a result of internal erosion. TELEVEV woven polyester fabrics can also be used to perform simple filtration tasks, to ensure that the overall system remains sufficiently permeable to water throughout the design life.
Reinforcement
The separation and filtering functions perfectly complement the main function of TELEVEV woven polyester fabrics: reinforcement. The use of soil-reinforcing geosynthetics is recommended in all situations where tensile strength is required in the soil in order to transfer the loads. In this composite system of soil and woven geotextile, loads are transferred to the geosynthetic material via shear deformations of the soil and are then distributed over a wide area. This is often the only way of ensuring the stability of an earthworks structure without resorting to additional measures.
The interaction between the shear strength of the soil and the tensile strength of the reinforcement
Deformation characteristics
In an earthworks structure reinforced using geosynthetics, the geosynthetic material and the soil work together. The soil becomes a technical construction material, whose load-bearing properties are improved and guaranteed in the long term by using TELEVEV woven polyester fabrics as tensile elements.
The two materials complement each other perfectly, whereby the more evenly the loads can be absorbed as tensile forces in the geosynthetic material and the surrounding soil, the more cost efficient the structure becomes.
TELEVEV woven polyester fabrics can act as tensile elements and absorb defined tensile stresses, while the soil itself can absorb the compressive stresses, thanks to its shear resistance.
Both the activation of the soil’s shear resistance and the increase in the geosynthetic’s tensile strength are dependent on the deformation. The maximum effective contribution that the soil can make to the load-bearing system is limited to its shear resistance.
This load-bearing effect of the soil is equivalent to the activation of its internal angle of friction. The manufacturing method and the selection of the right raw materials ensure that TELEVEV woven polyester fabrics, with their tensile strength/deformation behaviour, are ideal for use as soil reinforcement, so that the shear resistance of the soil is always used to its best effect. The decisive factor here is the technical information on tensile strength at 2% and 5% elongation, as stated in the data sheets.
The extensive TELEVEV product portfolio includes various different tensile strengths, so that the right material for the specific geotechnical requirements can always be found.
As a result, TELEVEV woven polyester fabrics are an important component of technically and economically optimised solutions in applied geotechnics.
Reduction factors
Their outstanding technical properties make TELEVEV woven polyester fabrics the ideal solution for complex and large-scale civil engineering structures. It is particularly important to take into account the specific reinforcing properties of the selected product when using these high-tensile materials. The long-term behaviour of the geosynthetic material under loading is particularly important and must be taken into consideration. To this end, specific reduction factors are used to determine the long-term strength from the initial short-term tensile strength, as measured immediately after production. These factors take into account the reduction in strength caused by the conditions on the construction site as well as by the demands of the structure throughout its intended service life.
The reinforcement’s creep behaviour under tension (A1), robustness with regard to installation and compaction on site (A2) and resistance to environmental influences (A4) are product-specific reduction factors applicable to TELEVEV woven polyester fabrics. They are used in determining the structurally-effective design strength for use in structural stability calculations.
These individual reduction factors were determined in the course of extensive long-term trials carried out by independent test laboratories or in large-scale trials on construction sites. Other effects that cannot be determined in trials are taken into account by incorporating a partial safety factor in the long-term tensile strength calculation.
In accordance with the recommendations of the German Society for Geotechnical Engineering (Deutsche Gesellschaft für Geotechnik e.V.) for the design and calculation of earth structures with geosynthetic reinforcement, the design tensile strength must be calculated using the following approach:
- RB,k0,5 Value of the short-term tensile strength of the geosynthetic material
- RB,d Design resistance of the geosynthetic reinforcement
- A1 Reduction factor for creep behaviour
- A2 Reduction factor for damage during transport, installation and compaction
- A3 Reduction factor for joints and connections (if applicable)
- A4 Reduction factor for environmental influences
- A5 Reduction factor for dynamic influences (if applicable)
- ?M Partial safety factor for material resistance (loading case 1: 1.4)
The short-term tensile strength can be found in the TELEVEV data sheets.
The individual reduction factors are determined for the particular product, taking into account the requirements of the structure and the construction site.
Application
Application of TELEVEV woven polyester fabrics
Due to the combination of the functions of separation, filtering and reinforcement in one single product, there are a large number of possible applications.
Tasks where reinforcement is required within the scope of infrastructure projects are typical applications for TELEVEV woven polyester fabrics. The spectrum of applications ranges from transport infrastructure, where the additional functions of separation and filtering play a decisive role in the success of the project, through to secondary support structures and special structures, where the reinforcement function is most important.
TELEVEV woven fabrics can be used in any situation where large areas need to be covered with a functional geosynthetic material. Because several design problems can be solved by one process and with just one product, they represent an excellent alternative to geogrids and combinations of products in which each performs a single function.
Also, the TELEVEV range covers a wide spectrum of tensile strengths, which means that individual solutions for a specific project can be tailored to suit the design requirements.
TELEVEV woven polyester fabrics can withstand very high tensile forces, making them highly effective in providing stability. Furthermore, by varying the degree of absorption of tensile forces, the expected deformations of the structure can be minimised and its fitness for use can be improved.
Columns wrapped in geosynthetic material
Circular-woven jackets made of TELEVEV woven polyester fabric are used as the basis for foundation systems with geotextile-encased columns. This method involves driving the geotextile jackets down to the load-bearing layer using steel pipes.
As the steel pipes are then withdrawn, the jacket is filled with non-cohesive fill material that has a high internal shear-resistance, whereby the geosynthetic jacket is subjected to radial stress.
The use of these geotextile jackets makes it possible to construct support members with significantly reduced bulging, whereby the sides of the members are supported sufficiently by the surrounding layer of softer soil in combination with the circular-woven casing. This allows even high loads to be transmitted through layers of soft soil into the load-bearing strata beneath.
As an added bonus, the water permeability of the fill material in the geotextile encased columns is usually significantly higher than that of the surrounding soft soil. Thus, the circular woven jacket can also act as a filter. Consequently, the use of TELEVEV encased columns helps to lower the pore water over-pressure in the surrounding soft soil more quickly and aids the settlement process.
Advantages
The advantages of TELEVEV woven polyester fabrics
- High tensile strength of up to 1,000 kN/m
- Multifunctional geosynthetic material – combines the functions of separation, filtering and reinforcement
- Aperture widths suitable for filtration purposes in most types of soil
- High chemical resistance
- Robust, to cope with installation conditions on site
- Easy to prepare and easy to lay
- Outstanding long-term durability with no reduction in performance
- Value for money
Many types of TELEVEV have IVG product certification (from the German Geosynthetics Industry Association) and are labelled with the “Güteüberwachung Geokunststoffe” quality seal for geosynthetics.
The products described here are harmless to the environment, as specified in the leaflet
“Merkblatt Geokunststoffe im Erdbau des Straßenbau” (Information leaflet on the use of geosynthetics in road construction earthworks), issued in 2005 by FGSV (German Road and Transportation Research Society).
All the values stated are guideline values. They correspond to the most recent knowledge available.
The right to make changes without notice is reserved.
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