This document is the Biaxial Geosynthetic Installation Guide. Site preparation, material placement and installation are explained.

For site preparation, the engineer shall verify the subgrade is ready for geogrid deployment, and that elevations are as indicated on the contract drawings. The surface shall be fairly smooth and free of stumps, sharp objects and debris that may damage the geogrid. Tree stumps should be cut at ground level. Care should be taken not to disturb any surface hard crust overlying weaker soils. In these cases, the geogrid should be installed directly on the unprepared subgrade. Recommended structural fill material should be well- graded crushed aggregate fill to provide good stability and low moisture susceptibility.

Structural fill gradation and geogrid overlap charts are included.

For installation, ADS Geosynthetic geogrids may be anchored in place to maintain the overlaps and alignments. Before fully unrolling the geogrid, anchor the beginning of the roll at the center and corners. Anchoring can be achieved by small piles of fill aggregate, washer pins, and U-staples driven in the subgrade capturing the apertures of the grid.

Unroll geogrids on the subgrade and apply tension to minimize wrinkles. Geogrid panel overlap requirements, either side-by-side, or end-to-end, shall depend on the strength of the subgrade. Adjacent geogrid rolls should be overlapped (shingled) in the direction of anticipated fill spreading. This is to avoid the “peeling” of the geogrid at overlaps. To minimize geogrid wrinkles caused by the shoving action, fill material shall be pushed forward and spread while gradually lifting the blade or bucket. A figure showing the fill spread direction is included.

Recommendations for base material placement over geogrid explains the process over firm subgrade, soft subgrade with repair and protection tips.