Improvement to bearing capacity

In the construction of heavily trafficked areas such as parking lots, a stable subgrade with sufficient bearing capacity is required. When installed between the subsoil and the base course, Secugrid® Q geogrids, made from high strength, extruded monolithic flat bars, with welded junctions, are particularly well suited for this application.

The coarse grained cover soil interlocks with the Secugrid® Q geogrid (grid apertures ≥ 28 mm) creating a bond. This immediate interlock provides a horizontal force transfer which increases the bearing capacity of the soil due to the high force absorption of Secugrid® – even under low elongation. The required bearing capacity can be achieved without additional expensive soil exchange, and in some cases, the base course thickness can be reduced.

Secutex® separation and filter nonwoven geotextiles are used to prevent the migration of fine particles into the base course. The design approaches for the nonwoven are described in further detail under the chapters “Filtration with geotextiles” and “Separation with geotextiles”. To facilitate the installation and create shear strength transfer, Secugrid® and Secutex® components are pre-manufactured into a bonded composite product – Combigrid®. On extremely soft subgrade, the bearing capacity can be markedly improved by using multiple layers of Secugrid® geogrids.

Reduction of rutting

When building unpaved roads (e. g. forest paths and temporary construction roads) on soft subsoil, rutting and inter mixing of the cover material into the subsoil should be avoided. Combigrid® or Secugrid® geogrids can significantly im prove load distribution, minimising rutting and soil intermixing. The selection of the Secugrid® geogrids is on a pro ject specific basis according to standard guidelines and site specific requirements (ask for the Secugrid® calculation tool).

Force-elongation-behaviour

Unlike the separation function of geotextiles, reinforcement requires a product with low elongation characteristics. Secugrid® geogrids have no product manufactured elongation. With the stiff junctions of the welded reinforcement bars, Secugrid® has less than 8 % elongation at break. For product comparisons and design issues, the force absorption at 2 % and 5 % elongation are often used.

Installation robustness

When installing and compacting coarse-grained cover soils and base course materials the reinforcement can be subjected to high dynamic stresses. Due to the thick, robust, monolithic reinforcement bars, Secugrid® geogrids and Combigrid® have a high resistance to installation loads.

Conclusion

In the construction of unpaved roads and highly trafficked areas, geogrid based geosynthetic system solutions are commonly used – especially on soft subsoils. Secugrid® geogrids are installed to improve the soil bearing capa city, to avoid expensive soil excavation and re compaction as well as to reduce the base course thickness in some instances. Combigrid® can effectively prevent the migration of fine particles into the base course.

Compared to conventional construction methods, the use of geosynthetics is an economical and effective alternative.