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- Retaining Wall - ( 1 - 11 )
- Design of Counterfort Retaining Wall - ( 12 - 21 )
- Design of Water Tank - ( 22 - 31 )
- Design of Rectangular Water Tank - ( 32 - 41 )
- Yield Line Theory - ( 42 - 43 )
- Upper and Lower Bound Theorems - ( 44 - 54 )
- Design of Staircase - ( 55 - 69 )
- Thread Riser Staircase - ( 70 - 72 )
- Design of Reinforced Concrete Wall - ( 73 - 78 )
- Design of Flat Slab - ( 79 - 89 )
- Design of Brick Masonry - ( 90 - 90 )
- Tests on Brick - ( 91 - 111 )
- Eccentrically Loaded Brick Masonry - ( 112 - 117 )
- Important Questions - ( 118 - 140 )

Topic:

CE2401 – Design of Reinforced Concrete & Brick Masonry Structures
Mr.R.PERUMAL.ME, AP/CIVIL, 9529/SCADEC
UNIT I
RETAINING WALL
Retaining wall – Retains Earth – when level difference exists between two surfaces
A) Gravity wall (h<3m) – Masonry or Stone
ww
w.E
asy
B) Cantilever wall (h>3m and h<6m)
C)
D) Counterfort wall (h>8m)
En
gin
eer
ing
.ne
_________________________________________________________________________________________________________________________
1
t

CE2401 – Design of Reinforced Concrete & Brick Masonry Structures
Mr.R.PERUMAL.ME, AP/CIVIL, 9529/SCADEC
E) Buttress wall [Transverse stem support provided on front side]
F) Bridge abutment [Additional horizontal restraint from bridge deck]
ww
Stability – Overturning and Sliding – Avoided by providing sufficient base width.
w.E
Earth pressure and stability requirements:
asy
En
gin
eer
ing
.ne
Pressure, P CJ e Z
Where, Z = depth, J e = Unit weight
Ca =
1 SinI
;
1 SinI
Always, Cp > Ca.
Cp
1 SinI
1 SinI
Eg: If ф = 300, Ca = 1/3 and Cp = 3.
In sloped backfill,
ª CosT Cos 2T Cos 2I º
Ca = «
»CosT ;
2
2
¬« CosT Cos T Cos I ¼»
Cp
1 SinI
1 SinI
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2
t

CE2401 – Design of Reinforced Concrete & Brick Masonry Structures
Mr.R.PERUMAL.ME, AP/CIVIL, 9529/SCADEC
1. Effect of surcharge on level backfill:
ww
w.E
Pa = Pa1 + Pa2, where,
Pa1 = Ca.W s.h = Ca.γe.hs.h &
Pa2 = Ca. γe.h2/2
[h/2 above heel]
[h/3 above heel]
asy
Note : Purpose of retaining wall is to retain earth and not water. Therefore, submerged
condition should be avoided by providing and maintaining proper drainage facilities
[including provision of weep holes].
2. Effect of water in the backfill:
Stability requirements
i) Overturning:
FOSoverturning =
En
FOS against
gin
eer
ing
.ne
Overtuning
≥ 1.4
Sliding
0.9 Mr
≥ 1.4
Mo
h'3
h'
= Ca. J e .
.Cos T
6
3
Mr = W (L – Xw) + (Pa.Sin T ).L
a) For sloping backfill, Mo = (Pa.Cos T ).
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3
t

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]
FOSsliding =
0.9 F
≥ 1.4
Pa CosT
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]
ww
w.E
asy
En
Pps
toe.
2
2
CJ e (h2 h1 ) / 2
gin
eer
ing
Xsk -> Flexural reinforcement from stem is extended straight into shear key near the
.ne
Note: For economical design, soil pressure resultant(R) must be in line with front face of
wall.
Preliminary proportioning of cantilever retaining wall:
1.
2.
3.
4.
5.
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'
¸
Lmin ¨
¨ 3 ¸D
©
¹ R
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
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4
t

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