Installation procedures of TENAX geogrids for soft soil reinforcement, Tenax geosynthetics

1. Clean the ground from debris, tree trunks, etc. Smooth and level the subgrade to the prescribed elevation and in order to provide adequate drainage.

2. Unroll the geogrids on site, providing the required overlapping. Rolls placed side by side or end to end shall be overlapped as shown in the table below, which provides a recommendation for the minimum overlap length based upon the subgrade shear strength. The overlapping shall be made in the direction of soil spreading to avoid geogrid uplift. The geogrids may be tensioned and fixed along the outer edges with "U" bars or with stones.

3. The truck shall move on previously laid soil, and generally NOT directly on the geogrids. Rubber tyre trucks may occasionally drive over the geogrid at very low speed (5 km/h) avoiding sudden stops and turns. Tracked vehicles shall never travel directly on the geogrids unless a minimum of 0,15 m fill cover protects the geogrid.

4. Two distinctive installation procedures shall be used based upon the existing subgrade shear strength encountered at the site:

Firm Ground Conditions: Unload the fill soil in a heap on the previously compacted soil or outside the geogrid covered area, thus preventing geogrid damage. The fill soil shall be spread on the uncovered geogrids by pushing with the bulldozer. Care must be given to impart also an upper vertical movement with the dozer blade, in order not to stress the under laid geogrids.
Soft Soil Conditions: Unload the fill soil in a heap on the previously compacted soil or on an area capable of supporting the weight of the soil. The fill soil shall be spread on the uncovered geogrids by pushing with a bulldozer. Care must be give to impart also an upper vertical movement with the dozer blade, to avoid stressing the under laid geogrids. On very soft soil conditions, the fill thickness is function of the construction procedure and the subgrade shear strength. In these conditions the use of a lightweight dozer and a minimum of 0.30m aggregate thickness is suggested before proceeding with compaction. If rutting and mud pumping develop during the installation due to equipment traffic, additional fill soil shall be added to strengthen the section. Ruts shall be always filled with soil and not graded.

5. Compact the soil to the prescribed density. Use only light equipment for compacting the first course on very soft subgrade. If required, wrap around the geogrids at the outer edges to enhance performances. If more than one geogrid layer is prescribed, repeat phases: 2, 3, 4, and 5. Lay and compact the asphalt in the usual way after settlements have taken place. In order to optimise geogrid performances, the following table suggests the typical fill grain size distribution. Different fill soil types have proved very effective in several projects worldwide.