The treatment of soft soil foundation with geogrid cushion is shown in the following aspects:
How geogrid and geotextile works in soft subgrade traetment:
- Geogrid has certain rigidity, which makes the load spread and improves the bearing capacity of the foundation.
- Because of the high tensile strength of Geogrid and geotextile, the existence of geogrid can increase the stability of embankment.
- As the grid can adapt to the deformation of the foundation, the gravel and the grid mesh can be locked together to form a stable plane, prevent the gravel from sinking, increase the shear strength of the foundation, so as to prevent the soft foundation from excessive or uneven settlement and lateral deformation.
- The function of gravel cushion and blind ditch. Sand gravel cushion can ensure good drainage of embankment. When there is soft soil foundation, sand gravel cushion and blind ditch form a comprehensive drainage channel. Through the upper embankment load, it can accelerate the drainage consolidation of soft soil foundation and complete most of the settlement in the construction stage.
Properties and requirements of geosyntehtics materials:
1.Clean sand gravel with particle size of 3-6cm and silt content less than 5% is required for gravel cushion to facilitate the formation of drainage channel.
2.The geogrid membrane is used in the grille, which is made of high density polyethylene (HDPE) and anti aging agent by extrusion rotary molding.It has the characteristics of high strength, corrosion resistance and long service life. It is light and convenient for construction.GTM geogrid, with longitudinal and transverse tensile strength ≥ 5.8n/m; mesh size of 27mm × 27mm; width of 30m; width of 2.5m; material standard weight of 660g / m2.
3.The Knitted woven geotextile is adopted, with the longitudinal breaking strength ≥ 2500n / m, the latitudinal breaking strength ≥ 200N / m, the elongation at break ≤ 25%, the longitudinal tearing strength ≥ 1200, the unit area mass of 240g / m2, and the amplitude of 4m.
How to install the geogrid:
1.First, level the site, remove the topsoil and drain the surface water.
2.The first layer of geogrid mesh shall be laid on the foundation. The grid shall be laid from one end of the treatment section, vertically, and one by one along the route.
The horizontal laying network is connected with the longitudinal blind ditch on both sides of the embankment, the overlapping length of the adjacent geogrid is 20cm, and the overlapping side is fixed with U-shaped nails.
In addition, at the place where the grid is close to the embankment, 2.5 shall be removed back to make the grid stable, and then 40 cm thick gravel with a particle size of 3-6 cm shall be paved on the grid. After leveling, use light roller to vibrate and roll for 3-5 times, then lay geotextile on gravel layer, and finally start to fill and roll in layers.
3.Subgrade soil shall be filled in layers and meet the requirements of corresponding specifications. In addition, it is necessary to avoid the direct rolling of the dumper on the grid which has been paved and tensioned.
4.During the construction, the filling rate of the embankment should be controlled and the observation of settlement and lateral displacement should be strengthened to prevent the embankment from instability.
In recent years, geotextile and geogrid are widely used in road engineering. It has different functions in different applications, such as isolation, anti-seepage, reinforcement, filtration drainage and protection. It is believed that the application prospect of geotextile and geogrid will be more bright in the future human road and urban road construction projects.