Combigrid® geogrids with integrated nonwoven geotextile component
Combigrid® is composite of a laid geogrid made of stretched, monolithic flat bars with welded junctions and a mechanical bonded geotextile welded within the geogrid structure.
Combigrid® soil reinforcement applications
- Base and subbase course stabilisation and reinforcement
- Basal reinforcement for embankments
- Load transfer platforms over piles (LTP)
- Bridging of mining voids and sinkholes
- Reinforced foundations
- Airport runways and graded portions
- Working platforms
- Pipe trenches
- Lagoons/Tailing ponds
Advantages of Combigrid® geogrids
- Reinforcement/stabilisation, filtration, separation, and drainage in just one product
- Immediate interlock with fill material (no construction-related strain)
- Excellent stress strain behaviour (high tensile stiffness)
- High radial stiffness and high cyclic tensile stiffness
- Robust against installation damage and chemical and biological attack
Selected advantages of Combigrid® multifunctional geogrids
Advantage 1: Multifunctional composite geogrid with excellent stress/strain behaviour
Geocomposites like Combigrid® are used wherever high strength is required at low elongation. The stress-strain behaviour, also known as tensile stiffness, of the geogrid is important when selecting which type of geogrid is to be used. Geogrids will typically have a maximum elongation at break of 6% up to 15%, depending on the choice of polymer and manufacturing technology. However, the internal angle of friction of medium to densely compacted soils is reduced when the soil is subjected to an elongation of less than 2%. It is necessary to align the stress-strain behaviour of the installed geogrids with the elongation behaviour of the soil.
The performance of the geogrids at a stress-strain ratio in the range of 2% is therefore important and here Combigrid® shows its strength. Combigrid® geogrids have excellent tensile strength properties at low elongations and demonstrate their advantages in this important strain range.
Stress-strain curves of different geogrids. Scaled up detail outlines typical working strain levels (≤ 2% elongation).
Advantage 2: Perfect soil separation with Combigrid®
The three-dimensional fibre matrix of the needle-punched Secutex® nonwoven, acts as separation layer between fine grained subgrade soil and coarse aggregate base course layers and ensures long-term filter stability. The properties of separation, filtration and reinforcement are combined in the product Combigrid®.
Tests to simulate the traffic passages on an un-reinforced base course resulted in 3 inch (75mm) deep ruts after 20 load cycles, and it took 540 load cycles when Secugrid® 20/20 Q1 was used. However, when Combigrid® geogrids were used, the maximum rut depth of 3 inches was not reached even after 100,000 load cycles. Using a composite product made of a geogrid and a nonwoven needle-punched geotextile firmly bonded between the longitudinal and cross bars at the interface between soft sub-grade and base course layer worked really well.
Combigrid® and Secugrid® traffic benefit ratio (TBR) over a very weak subsoil, compared to an unreinforced design (for subsoils CBR 1 %, for details see EuroGeo4, paper 229)
Combigrid® geogrids the geocomposite reinforcement solution
Combigrid® geocomposites benefit from NAUE’s decades of reinforcement experience. Continuous improvement of the manufacturing process, stringent quality control in raw material selection and expert engineering support ensure safe and economical constructions.
Combigrid® is a geocomposite reinforcement solution. The unique manufacturing process produces structured, high strength, monolithic, pre-stressed polypropylene or polyester bars with a continuous molecular structure. The extraordinary high extensional stiffness of Combigrid® efficiently reduces deformations in the subgrade which extends the service life of modern infrastructure.
Reinforcement stabilisation, filtration, separation and drainage in a single product
The geocomposite additionally embeds a Secutex® nonwoven geotextile within the stretched bars. The welding process that strongly joins the longitudinal and transverse bars, creates a firm and robust geocomposite for use in stabilised and reinforced foundation layers.
This combination provides reinforcement stabilisation, filtration, separation and drainage in a single product
The geogrid / nonwoven geotextile composite is used primarily on soft soils with low bearing capacity, such as unbound, dynamically loaded layers that require filtration and separation support. Typical applications include base and subbase stabilisation and reinforcement for temporary and permanent roads, railways, storage yards, container terminals, temporary working platforms, airport runways, sludge lagoons and tailings ponds.
Geogrid documents download