Contents
Geogrid application
Volumetric geogrid is used for slope strengthening, protection of embankment slopes against erosion, protection of bridge abutments and inundated embankment foundations, reinforcement of weak embankment foundations, as well as landscaping.
Geogrid use allows to:
- simplify handling of weak soil;
- shorten construction time;
- lower the risk of soil uneven settlement and frost heaving;
- increase the road pavement service life;
- increase inter-repair spans.
Geocell application range covers:
- erosion protection and strengthening of motorway and railway slopes, and bridge and viaduct abutments;
- the road pavement weak base and sub-base reinforcement when building permanent and quick roads, oil & gas facilities and construction sites;
- construction of retaining walls, steepening of road and site slopes;
- reinforcement of the subgrade upper part soil;
- reinforcement of surface water evacuation systems in road, hydraulic and infrastructural construction.
Volumetric geogrid is an arrangement of cells made of polymeric strips bonded by strong weld joints in a chess order.
Geocells are issued as foldable modules that, when folded are shaped as a rectangular package, and in an unfolded working condition comprise a cell structure. The geocell folded condition is characterized by the absence of gaps between its adjacent layers. The geocell module unfolded condition (geocell module ready to be installed on the ground surface) is characterized by the equal size of the cell diagonals in mutually perpendicular directions.
Geogrid preparation and installation
Before geogrid installation on a horizontal surface, its modules are transported and spread over the site, with foundations for their laying prepared in a certain way.
Before geogrid installation on a horizontal surface, the module borders are marked, and temporary anchor rods are fixed along one side in longitudinal direction (parallel to the subgrade axis).
Geogrid laying should be done manually. Geogrid outmost cells are put on the anchors, and the geogrid is spread and fixed by temporary anchor rods on the other side. The adjacent modules are also prefixed by anchor rods (placed in transverse direction) and then finally fixed with special staples. Stapling should be done at several points of every cell along its height, approximately every 2.5 cm, followed by anchoring. Alignment and proper sizing should be under control.
Geogrid cell filling
What is the right way to fill the cells? Geogrid cell filling should be done in two stages:
As the first stage, the outmost cells of every section should be filled manually to allow the anchor rods removal;
As the second stage, the remaining cells should be filled in the direction of travel, with the filler movement by a lift truck and its spreading by a bulldozer. The building equipment can start moving only after the cells have been excessively filled, i.e. more than 5 cm over the geogrid, thus providing a protective layer. Such a layer thickness post compacting should be not be less than 5 cm in case of macadam and 3 cm in case of sand. The filler compacting is normally conducted by vibratory compactors or pneumatic-tired rollers.
As may be directed by the project design, an armoring woven synthetic material (e.g. Geospan GT PP) may be placed directly under the geogrid to strengthen the soil reinforcement structure.
Conclusions
Volumetric geogrid is a geosynthetic modular material widely used in construction of roads and railroads, bank reinforcement and other geotechnical projects.
Volumetric geogrid is included in Geospan range as Geospan GC.
Geospan GC is a geogrid with unperforated geocells.
Geospan GCP is a geogrid with its geocells punched. It is used in the designs requiring enhanced drainage and geocell friction with the filler, or cable bracing. A round aperture has a diameter of 10 mm. The distance between the aperture centers of each row is at least 19 mm. The horizontal aperture rows are positioned in a chess order with their distance from the apertures center line amounting to at least 12 mm.
