9.6 Low retaining walls with gabions

Sources

1. Hertfordshire County Council, standard drawing HST-0600-001 Typical gabion retaining walls: fill graded 100–200 mm; welded mesh 75 × 75 mm; retained height 350–550 mm with one 1.0 × 1.0 m gabion, up to 1.5 m with a 1.5 m wide gabion under a 1.0 m one; gabions buried 300–500 mm; face batter 6°; foundation of compacted well-graded granular fill or concrete, at least 50 mm wider than the basket on each side; bracing wires after ⅓ and ⅔ of the height, end units braced both ways; no compartment more than 300 mm higher than its neighbour; exposed faces hand packed; vertical joints staggered; slight overfill where gabions are stacked; geotextile behind the gabions and on all buried faces
2. FHWA Federal Lands, standard drawing E253-01 Gabion retaining wall: rock-filled gabions weigh 110 lb/ft³ (about 1.75 t/m³); front face battered 1:12; underdrain at the back with outlets
3. Kentucky Transportation Cabinet, standard drawing RGX-050 Gabion retaining walls: front face battered 6:1 or stepped; a special design is needed where the slope above is steeper than 2:1 or where a load sits close behind the wall
4. Cessnock City Council (NSW), AUS-SPEC 0294 Gabion walls and rock filled mattresses: rock sized for at least three layers in a gabion; 1 m gabions filled in three layers with bracing after the first and second; 500 mm gabions in two layers of 250 mm; bracing wires at 330 mm; exposed faces placed by hand; overfill 25–50 mm; prepared foundation sloping at most 1 in 10; geotextile between gabions and retained soil; heavy plant kept 1 m from the units
5. Wyndham City Council (Victoria), Technical Specification 715 Gabions and rock mattresses: gabion rock 100–250 mm with at least two broken faces, free of laminations and cracks; welded mesh at most 75 × 75 mm; braces at about 330 mm after filling ⅓ and ⅔; refill where bulges exceed 50 mm; perforated drain pipe at least 100 mm at the base of the rear of a gabion retaining wall
6. South Australia Department for Infrastructure and Transport, Master Specification ST-RE-C3 Gabions: gabion rock 100–250 mm with a range of sizes and some angularity; backfill in loose layers of at most 200 mm; only hand-operated plate compactors within 1 m of the back of the gabions
7. Tennessee Erosion and Sediment Control Handbook, Gabions: clean 100–200 mm stone without fines, sized to stay in the baskets, preferably placed by hand; geotextile behind all gabion structures; gabions keyed into the foundation
8. City of Arvada (Colorado), Retaining walls: permit and engineer-stamped drawings for retaining walls over 4 ft (1.2 m) measured from the bottom of the footing, and for any wall carrying a surcharge
9. City of Delano (Minnesota), Retaining walls: retaining walls over 4 ft (1.2 m) from the bottom of the footing need an engineered design
10. US Department of Defense, UFGS 31 36 00 Gabions: rock 100–200 mm for gabions 500 mm and taller, large enough not to pass the mesh; at most 5 % oversize or undersize, undersize only inside, never on the face; room for three or more layers of rock per compartment; hard, angular to round, durable rock that does not break down in water or weather, with freeze-thaw testing; at most 5 % dirt, sand, clay and fines; 300 mm lifts, no cell more than 300 mm higher than its neighbour; stiffeners at ⅓ and ⅔ of the height; hand-placed visible faces; drop height at most 0.9–1.2 m; overfill 25–50 mm; no foundation work on frozen ground
11. FHWA Federal Lands, standard drawing W253-3: filled gabions weigh 105 lb/ft³ (17.6 kN/m³, about 1.7 t/m³)
12. FHWA-RD-97-148, Granular base: natural aggregates weigh about 2.0–2.3 t/m³ in place
13. EN 13242 Aggregates for unbound and hydraulically bound materials

Amounts per metre of wall, one 1.0 × 1.0 m course: stone 1 m³ × 1.7–1.8 t/m³ (FHWA design weight of filled gabions). Base 1.1 m × 0.2 m (9.3) = 0.22 m³ at 2.1 t/m³ = 460 kg. Drainage stone 300 mm wide × 1.0 m high, as for block walls (6.3).