The function of geogrid is to compound geotextiles with various fillers to enhance the bearing capacity of the roadbed. Usually the fillers used are lime soil, expanded perlite, gravel, river pebbles, etc., among which lime soil is most commonly used. Geogrid, also known as plastic film geotextile or plastic drainage network, is a fabric made of polymer. It is mainly composed of warp knitting, weft knitting silk and non-woven fabric. It is a kind of product that is made by cutting slots in plastic film, putting the plastic film into the machine, and using plastic needle to pierce the mesh holes to make a grating-like product. It is generally used in soft ground, slope protection of dams, roads and railroads. Common geogrid products are: polypropylene (PP), polyethylene (PE), modified polypropylene (PP/PP), polyvinyl chloride (PVC/PVC), etc.
1、Base layer
The base layer of geogrid usually includes gravel, sand and gravel or cement stabilized soil, etc. In order to achieve better strength and better drainage effect, a certain amount of gravel or gravel is generally added to the gravel layer to increase the strength and shear resistance. If the roadbed is high and the foundation strength is not enough, geogrid can be added at the foot of the embankment slope and shoulder. Geogrid has good effect on foundation treatment. The thickness of the grating in the roadbed can be set according to the need, generally set to 20-50 mm/100 mm×100 mm.
2、Fill
Geogrid in the filling section should be filled in the order of high first and then low. The fill section shall be filled in layers from top to bottom, and the fill and excavation shall be 15m wide. (3) When ramming or mechanical rolling is used, the site should be inspected and leveled before construction to ensure the surface is smooth, dense and without cracks; if there is unevenness at the site, it should be trimmed before construction.
3、Tendon material
Geogrid is divided into twisted spun geotextile and untwisted spun geotextile. Twisted spun geotextile (grating), made of non-twisted textile as the base material, adding glass fiber, plastic fiber and rubber strip wire, etc. Twist-free spun geogrid, also known as plastic film geotextile, is made of polypropylene film as the base material and treated with surface coating to form a non-woven material that can be used directly on the roadbed. Polyethylene plastic film (PE film), produced from polypropylene as raw material by melt drawing process. Polyethylene plastic film (PE film), also known as PVC film, CPP or polyvinyl chloride plastic film (PVC film), is made of chloroacetylene as raw material.
4、Joint between geogrid and filler
During construction, the lap length of geogrid should be not less than 1m. (1) When the height of the fill is large, it is generally not less than 2 times the height of the slope (the height of the fill can be calculated according to the following formula: m=1.33), and not more than 3 times the height of the slope, so that the height of the fill is not too large for construction. (2) When the width of the bottom of the road graben is greater than 1 meter, the geogrid should be laid first within 10 meters of the bottom width of the hand-dug road graben. (4) When the width of the bottom of the graben is greater than 1.5 meters, the geogrid should not generally be in direct contact with the fill. (5) The filling construction on the slope of the road graben should be completed before the rainy season to avoid the accident of destabilization caused by the rain washing the slope.