Compacted and stable subgrade soil should be prepared to all specifications, lines, grades, and cross sections shown on the final drawings. Termination trenches, embankment crests, and toes should all be compacted and graded to ensure that water cannot migrate under the block and geotextile material at these points.
Final subgrade should be graded smooth to ensure complete contact with the geotextile and ACBs. Unacceptable soils, soils to wet too achieve compaction, and soils with debris in them should be removed and replaced with approved material and compacted to specifications.
- Remove all surface vegetation and debris. This removed material should not be used as backfill or placed back on the surface. Prepare the surface for installation of the ACB system.
- When installing ACB systems the subgrade must be stable prior to installation. ACB systems maintain slope stability and prevent erosion, but are not slope stabilization systems. For this reason the subgrade must be as clean and level as possible.
- The block systems are designed to allow for block protrusions of one-half inch on random blocks. However, the goal is to minimize non-conformities in the subgrade. Geotextile products are strong and durable, but the area to be covered should be free of debris or any materials that may tear or puncture the geotextile.
- Compaction of the subgrade should be to 90% - 95% of standard proctor. This insures that the soils are stable and will not erode when water is flowing over and through the installation.
- After preparation of the subgrade installation of the geotextile can begin.
At the completion of rough grading, soil samples representative of subgrade conditions shall be obtained according to current best practices, and tested for the following:
- Grain size distribution (ASTM D 422)
- Atterberg Limits (ASTM D 4318)
- Standard Proctor Density (ASTM D 698)
Results of laboratory tests shall be submitted to the engineer to ensure conformance with design parameters prior to placement of the geotextile and ACB revetment system. When a granular filter is used, it shall be tested for grain size distribution at the same frequency as the subgrade soil testing.
Spreader Bar | Subgrade Preparation | Geotextile Installation | Loading and Unloading Cabled Mattresses
Placement of ACBs | Cabling, Anchoring and Crimping | Grouting | Bibliography