RCC · retaining wall
Retaining wall — cantilever or counterfort
1
Wall and design mode
spec §5, §7
Wall
Design mode
B 3.25 m · toe 1.00 · heel 1.80 m · stem 200–450 · base 300 mm · key 1000 × 300the spec's loop · base widened, stem and base thickened until the wall stands
A cantilever wall: the fill level with the top, a surcharge on it and IS 14458 (Part 8)’s share of the water behind and under it, the stem’s earth face vertical and its taper on the front. Designed per metre run. The base starts at 0.4 H with the toe at α B and widens 50 mm at a time until the wall stands, at most to 1.0 H; where sliding alone fails, a shear key under the stem is built first, 300 mm deep and 50 mm deeper a pass, to the depth set under the ground.
2
Backfill, surcharge and water
Rankine's active · at rest · IS 14458 (Part 8) cl 5.1, 5.2
Use the cohesion
Pressure on the members
Ka 0.3333 · P 74.88 kN/m at 1.363 m · K₀ 0.5000 on the membersno tension crack
3
Ground under the base
read as gross · IS 14458 (Part 2) cl 6.1
Shear key where sliding asks
q 73.9 / 29.7 kPa against 150FOS 2.47 overturning · 1.75 sliding · key 1000 mm
4
Materials and cover
Tables 3, 5, 16 · cl 26.4.2.2
Grade of concrete
Grade of steel
Exposure
Moderate needs M 25 — M 25 clears itcover 50 / 40 / 50 mm
5
Reinforcement
the smallest placeable size
Main bar sizes permitted
stem 16 Ø @ 160 · toe 10 Ø @ 100 · heel 16 Ø @ 150 · key 10 Ø @ 140stem bars run the full height
6
Factors and proportions
Table 18 · factors of safety
Overturning and sliding are held to IS 14458 (Part 8) cl 5.2’s 2 and 1.75 on the whole restoring load. The concrete is weighed at 22.75 where it resists and 25 where it loads.
7
Not designed here
spec §12
This version does not design for sloping backfill, compaction-induced earth pressure, seismic earth pressure (IS 1893), buttresses — counterforts on the front, passive resistance in front of the toe, but on a shear key's face, crack widths, a base of two thicknesses, a wall founded on rock. A wall that needs any of them is outside it.