It is a power point presentation on Counterfort Retaining wall.

1. Enrollment No . Name
130120106039 KAIZER DAVE
130120106045 KISHAN VYAS
130120106061 BINOY PATEL
Internal Guide: Prof. Jay Sir
Prof. Sandeep Sir
1
Gandhinagar Institute of
Technology: Department of
Civil Engineering
Design of Reinforced concrete Structure (2170607) -
COUNTERFORT RETAINING WALL
GANDHINAGAR INSTITUTE OF
TECHNOLOGY

2. RETAINING WALL
• A Retaining wall is a structure used to retain the
earth or other materials and to maintain ground
surface at different elevations on either side of it.
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3. RETAINING WALL TERMINOLOGY
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4. TYPES OF RETAINING WALLS
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• Gravity retaining walls.
• Cantilever retaining walls.
• Counterfort retaining walls.
• Buttress wall.
• Bridge abutment.
• Box culvert.

5. Gandhinagar Institute of Technology :
Department of Civil Engineering
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Gravity retaining wall
Cantilevered
retaining
wall
Precast concrete
retaining wall
Precast concrete crib
retaining wall Sheet pile wall

6. COUNTERFORT RETAINING WALL
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• In the counterfort retaining wall,
the stem and the base and the
base slab are tied together by
counterforts, at suitable
intervals. Because of provision of
counterforts, the vertical stem as
well as the heel slab acts as a
continuous slab, in contrast to
the cantilevers of cantilever
retaining wall.
• Counterfort retaining walls are
economical for height over about
6m.

7. FORCES ACTING ON RETAINING WALL
• Lateral earth pressure
• Self weight of retaining wall
• Weight of soil above the base
slab
• Surcharge, i.e. forces due to
loads on earth surface.
• Soil reaction below base slab
• Frictional force at the bottom
of base slab
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8. Earth Pressure (P)
• Earth pressure is the pressure exerted by the
retaining material on the retaining wall. This
pressure tends to deflect the wall outward.
• Types of earth pressure :
• Active earth pressure or earth pressure (Pa)
and
• Passive earth pressure (Pp).
• Active earth pressure tends to deflect the wall
away from the backfill.
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9. Factors affecting earth pressure
• Earth pressure depends on type of backfill, the
• height of wall and the soil conditions
• Soil conditions: The different soil conditions are
• Dry or moist backfill with no surcharge
• Submerged backfill
• Backfill with uniform surcharge
• Backfill with sloping surface
•Inclined back and surcharge
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10. (1)Analysis for dry back fills with no
surcharge
• Maximum pressure
at any height,
p=kaϒh
• Total pressure at any
height from top,
𝑃𝑎 =
1
2
ϒ𝑘 𝑎 𝐻2
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11. • 𝑘 𝑎= Coefficient of active earth pressure
= (1-sinΦ)/(1+sinΦ)=𝑡𝑎𝑛2
Φ
= 1/𝑘 𝑝, coefficient of passive earth
pressure
= Angle of internal friction or angle of
repose
ϒ=Unit weight or density of backfill
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12. (2) Submerged backfill
• Lateral pressure due to submerged weight of soil
= 𝑘 𝑎ϒH
• Lateral pressure due to water, =ϒ 𝑤H
• Total pressure at base,
𝑃𝑎 = 𝑘 𝑎ϒH+ϒ 𝑤H
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13. (3)Backfill with uniform surcharge
• The lateral pressure due to
surcharge,
=𝑘 𝑎q
• The lateral pressure due to
backfill,
=𝑘 𝑎ϒH
• Lateral pressure intensity at base,
𝑃𝑎= 𝑘 𝑎q+𝑘 𝑎ϒH
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14. (4) Backfill with sloping surface
• The total earth pressure
acts at an angle β with
horizontal.
𝑘 𝑎=cosβ
𝑐𝑜𝑠𝛽− 𝑐𝑜𝑠2 𝛽−𝑐𝑜𝑠2 ∅
𝑐𝑜𝑠𝛽+ 𝑐𝑜𝑠2 𝛽−𝑐𝑜𝑠2 ∅
• β=angle of surcharge
• If surcharge is
horizontal,β=0
Therefore, 𝑘 𝑎=
1−sin ∅
1+sin ∅
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15. (5) Inclined back and surcharge
• Resultant of pressure
𝑃1 and weight of soil
wedge W is calculated
as
P= 𝑃1
2
+ 𝑊2
where 𝑃1=
1
2
ϒ𝑘 𝑎 𝐻2
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16. Stability Conditions
• The retaining wall should
satisfy the following
stability condition-
•Stability against
overturning
•Stability against sliding
•Maximum pressure at
base should not exceed
safe bearing capacity of
soil.
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17. Stability against overturning
• As per IS:456-2000, CI.20.1, factor of safety against
overturning should not be less than 1.4.In case
where dead load provides the restoring moment,
only 0.9 times the characteristic dead load shall be
considered.
Hence ,the factor of safety is given by relation,
F.S=
0.9 𝑟𝑒𝑠𝑡𝑜𝑟𝑖𝑛𝑔 𝑚𝑜𝑚𝑒𝑛𝑡
𝑜𝑣𝑒𝑟𝑡𝑢𝑟𝑛𝑖𝑛𝑔 𝑚𝑜𝑚𝑒𝑛𝑡
≥ 1.4
=
𝑀 𝑟
𝑀 𝑜
≥ 1.55
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18. Stability against sliding
• As per IS:456-2000, CI.20.2, factor of safety against
sliding should not be less than 1.4.In this case also
0.9 times characteristic dead load shall be taken
into account.
F.S=
0.9 𝑟𝑒𝑠𝑡𝑜𝑟𝑖𝑛𝑔 𝑓𝑜𝑟𝑐𝑒
𝑠𝑙𝑖𝑑𝑖𝑛𝑔 𝑓𝑜𝑟𝑐𝑒
≥ 1.4
=
0.9(𝜇∙∑𝑊)
𝑃 𝑎ℎ
≥ 1.4
=
(𝜇∙∑𝑊 +𝑃 𝑝)
𝑃 𝑎ℎ
≥ 1.55
Where,µ=coefficient of friction
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19. Maximum pressure at base should not
exceed safe bearing capacity of soil.
• The intensity of soil pressure at toe,
𝑃max=
∑𝑊
𝑏
[1 +
6𝑒
𝑏
]……….at toe
𝑃 𝑚𝑖𝑛=
∑𝑊
𝑏
[1 −
6𝑒
𝑏
]………..at heel
• 𝑝 𝑚𝑎𝑥 should not exceed safe bearing capacity(SBC)
of soil.
• For no tension, 𝑝 𝑚𝑖𝑛 should not be negative.
Gandhinagar Institute of Technology : Department of Civil Engineering 19