CE2401 – Design of Reinforced Concrete & Brick Masonry Structures
Mr.R.PERUMAL.ME, AP/CIVIL, 9529/SCADEC
b) For level backfill [with surcharge, Mo = (Pa1(h/2) + (Pa2(h/3).
Mr = W (L – Xw)
[as T = 0o]
ii) Sliding: [Friction between base slab and supporting soil]
F = μ.R
[where, R = W ]
R -> Resultant soil pressure at footing base
μ -> Coefficient of static friction [0.35 – Silt & 0.60 – Rough rock]
When Pa is very high, shear key projection can be provided below footing base [Produces
passive resistance Pps, which is generally neglected, otherwise].
Sliding is reduced by providing shear key [like a plug, anchors inside]
CJ e (h2 h1 ) / 2
Xsk -> Flexural reinforcement from stem is extended straight into shear key near the
Note: For economical design, soil pressure resultant(R) must be in line with front face of
Preliminary proportioning of cantilever retaining wall:
The thickness of base slab is h/12 or 8% of the height of wall + surcharge.
The base thickness of stem should be greater than the thickness of base slab
The top thickness of stem should not be less than 150mm.
Clear cover for stem is 50mm and base slab is 75mm
Minimum length of base slab is given by
§ C a · h'
¨ 3 ¸D
where, αR = Coefficient depending on the pressure distribution
αR = 0.5 for rectangular pressure distribution & 0.67 for trapezoidal pr.dist.
6. Minimum length of heel slab is given by