DESIGN OF RCC ABUTMENT UNDER SLRB 2.300 1.400 0.000 0.900 + 0.275 + 0.300 A + 20.929 0.000 2.000 E B 3.200 D C 0.600 + 2.300 2.000 7.500 Using M-20 grade concrete, the design parameters to be adopted ar = 200 = 6.67 m = 13.993 k = 0.318 j = 0.894 Q = 0.948 DIMENSIONS OF THE BASE:- Length of the toe = 2.000 m Length of the heel = 2.000 m Thickness at the top = 1.4 m Thickness of the bed block = 0.9 m Thickness at the bottom = 2.3 m Height of the stem = 20.929 m Thickness of the base slab = 2m = 15.329 m Unit weight of soil considered = 21 Unit weight of concrete considere = 25 W1 W2 W3 W6 W4 W5 sst N/mm 2 scbc N/mm 2 Height of the wall H KN/m 3 KN/m 3 Bforce Fforce Rreaction
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DESIGN OF RCC ABUTMENT UNDER SLRB
2.3001.400 0.000
0.900 + 338.715
0.275 + 338.440
0.300 A + 338.140
20.929
0.000
2.000 E B 3.200 D C 317.786
0.600+ 316.986
2.3002.000 7.500
Using M-20 grade concrete, the design parameters to be adopted are the following
= 200
= 6.67m = 13.993k = 0.318j = 0.894Q = 0.948
DIMENSIONS OF THE BASE:-Length of the toe = 2.000 mLength of the heel = 2.000 mThickness at the top = 1.4 mThickness of the bed block = 0.9 mThickness at the bottom = 2.3 mHeight of the stem = 20.929 mThickness of the base slab = 2 m
= 15.329 m
Unit weight of soil considered = 21
Unit weight of concrete considered = 25
W1
W2
W3
W6
W4
W5
sst N/mm2
scbc N/mm2
Height of the wall H
KN/m3
KN/m3
BforceFforce
Rreaction
Angle of internal friction = 32
= 0.307Value of Kp = 3.257Reaction coming on to the abutment = 35.069 KNBreaking force = 0 KNFrictional force = 0 KNSafe bearing capacity of the
soil considered = 600Coefficint of friction between soil and concrete = 0.6Clear cover provided = 0.075 m
804 Main reinfortcement provided(Toe) = 32 mm804 Main reinfortcement provided(Heel) = 32 mm201 Distribution steel provided(Heel) = 16 mm201 Distribution steel provided (stem) = 16 mm804 Main reinfortcement provided (stem) = 32 mm
0 Consider a live load surcharge of = 0 m
DESIGN
Minimum depth of foundation
Ka =
Ka = 0.307
d = 600 / 21 x 0.307²= 2.693 m
However provide d = 2.25 m below ground level
The ratio of the length of the toe slab to the base width b is given by
a =
Where H = Height of the wall including thickness of the base
a = 1 - 600 / ( 2.2 x 21 x 22.929)= 0.153
Width of the baseb =
Value of Ka
KN/m2
d=q0
γ×( 1−sinφ
1+sinφ )2
( 1−sinφ1+sinφ )
1−q0
2 . 2×γH
0 .95×H×2√ K a
(1−α )×(1+3α )
= 0.95x15.329x(0.307/(1-0.153)x(1+3x 0.153))^0.5= 7.258 m
The base width with respect to slidingb =
= 0.7 x 15.329 x 0.307( 1 - 0.153) x 0.6
= 6.482 m
Provide b = 0.6Hb = 9.197 m
Provide 7.500 m
Width of toe slab == 1.148 m
Provide 2.000 m
Thickness of the base slab= H / 12= 1.277 m
Provide 2 m
Thickness of the stem
= 15.329 m
Considering 1m length of the retaining wall
=
= 3870.329 Kn-m
Effective depth required = 2020.551 mm
Effective depth provided = 2209 mmHENCE SAFE
a x b
Height H1
Max bending moment at B KagH13/6 + KawH1
2/2
0 .7×H×Ka(1−α )×μ
Stability of wall
S.NO Designation Force MagnitudeLever arm
1 1.4 x 0.275 x 25 9.625 3.6 34.65
2 0.9 x 0.3 x 25 6.75 2.45 16.538
3 1 x 2.3 x 20.354 x 25 1170.355 3.15 3686.618
4 0.5 x 0 x 20.354 x 25 0 2 0
5 2 x 7.5 x 25 375 3.75 1406.25
6 3.2 x 20.929 x 21 1406.429 5.9 8297.931
7 3.2 x 0 x 21 0 5.9 0
8 35.069 35.069 2.45 85.919
9 0 0 21.454 0
10 0 0 21.454 0Total 3003.228 KN 13527.91 KN - m
Total resisting moment
= 13527.906 KN - m
Earth pressureP = 757.452 KN
Check for over turningOver turning moment = 3870.327 KN - m
Factor of safety against over turining moment = 3.495 > 2SAFE
Check for slidingFactor of safety against sliding = 2.379 > 1.5
SAFEAs the section fails against sliding provide a shear key
Moment about toe
W1
W2
W3
W4
W5
W6
W7
RREACTION
BForce
FForce
Mr
Pressure distributionNet moment
= 9657.579 KN - mLever arm from toe = 3.216 m
Eccentricity e = 0.534 m
= 1.250 m
= 571.49
= 229.37
Pressure P at the junction of the stem with toe slab
= 480.26
Pressure P' at the junction of the stem with heel slab
= 425.52
Design of toe slab 1.40.9
A
2.3002.000 B 3.200
D C0.400
7.5002.000
229.37571.49
480.26 425.52
SM
emax
Pressure P1 at toe P1 KN/m2
Pressure P2 at heel P2 KN/m2
KN/m2
KN/m2
The weight of the soil above toe slab is neglectedThe forces acting on it are
(i) Up ward soil pressure(ii) Down ward weight of slab
Down ward weight of slab per unit area = 50
Net pressure intensity under D = 521.49
Net pressure intensity under E = 430.26
Total force = shear force at E = 951.754 KN
x from E = 1.032 m
Bending moment at E = 982.21 KN - m
Effective depth required d = 1017.883 mm
Effective depth provided = 1909 mmHENCE SAFE
Area of steel = 2877.603
This reinforcement is provided at the bottom face with a spacing of.= 275 mm c/c
= 2923.055HENCE SAFE
32mm dia bars at a spacing of 275mm C/C
Distribution steel = 0.15% of area
= 2250
Provide 16mm dia bars at a spacing of = 85 mm c/c
KN / m2
KN / m2
KN / m2
Ast mm2
mm2
mm2
Design of heel slabThe forces that are acting on it are
(i) Down ward weight of soil(ii) Down ward weight of heel slab
(iii) Up ward soil pressure
(i) Down ward weight of soil = 1406.429 KN
Acting at = 1.6 m from B
(ii) Down ward weight of heel slab = 160 KN
Acting at = 1.6 m from B
(iii) Up ward soil pressure = 1047.819 KN
Acting at = 1.44 m from B
Total force = Shear force at B = 518.61 KN
Bending moment at B = 997.427 KN - m
Effective depth required d = 1025.738 mm
Effective depth provided = 1909 mmHENCE SAFE
Area of steel = 2922.185
Required 32mm dia bars at a spacing of = 275 mm C/C
Provided 32mm dia bars at a spacing of = 95 mm C/C