Installation Guideline: BaseGrid Base Stabilization Geogrids

Preparation

  1. The engineer should verify the subgrade is ready for BaseGrid base stabilization geogrid placement and that elevations are as indicated on the contract drawings.
  2. The surface should be fairly smooth and free of stumps, sharp objects and debris that may damage the base stabilization geogrid. Tree stumps should be cut at ground level.

Installation

  1. Unroll BaseGrid geogrid on the subgrade and apply tension to eliminate wrinkles.
  2. Geogrid panel overlap requirements, either side-by-side or end-to-end, should depend on the strength of the subgrade.
  3. For very soft subgrade (with CBR = 1-2), 2 feet overlap is recommended.
  4. For firm subgrade (CBR > 2), 1 foot overlap is recommended.
  5. Adjacent BaseGrid geogrid rolls should be overlapped in the direction of anticipated fill spreading.

Base Material Placement Over the Geogrid

FIRM SUBGRADE

  1. When applying the fill material over firm ground (CBR > 2), rubber tire trucks (end and belly dumps) can drive directly on the geogrid at very slow speeds (less than 5 mph) and dump the fill material as they go.
  2. Operators must not turn or make any sudden stops when driving across the BaseGrid geogrid.
  3. Tracked vehicles cannot be driven on the geogrid.
  4. A minimum of four inches of fill material should be placed between the BaseGrid base stabilization geogrid and tracks.

SOFT SUBGRADE

  1. When applying fill material over soft ground (CBR between 1-2) and very soft ground (CBR <1), no equipment can drive directly on the BaseGrid geogrid.
  2. A minimum of four inches of fill is required between the base stabilization geogrid and the operating vehicles.
  3. Tight turns, sudden stops or spinning tracks are prohibited.
  4. Low ground pressure tractors and low tire pressures (less than 4 psi) are recommended for hauling and spreading fill over soft subgrade.
  5. Back dump specified fill materials onto the base stabilization geogrid where the subgrade is most stable and then spread the fill over the geogrid out toward the weaker subgrade.
  6. Haul trucks should not drive on the fill material until total compacted fill thickness has been achieved.
  7. Any ruts developed during spreading or compacting must be filled with additional fill material to reach the design thickness.
  8. Base course material should be placed and compacted in the lift thickness specified in the design requirements.

Repair

  1. BaseGrid geogrid sections damaged during installation must be repaired by patching. Place a geogrid patch to cover damaged geogrid area and extend 3 feet beyond in all directions.

Protection

  1. The BaseGrid base stabilization geogrid should be protected from long-term exposure to direct sunlight during transport and storage.
  2. After placement, the geogrid should not be left uncovered for more than 3 weeks.