retaining wall

RETAINING WALL

Retaining wall:

Retaining walls are structure used to retain soil, rock or other materials in a vertical condition.Hence they provide a lateral support to vertical slopes of soil that would otherwise collapseinto a more natural shape.

Most common materials used for retaining walls are:- Wood sheets;- Steel and plastic interlocking sheets;- Reinforced concrete sheets;- Precast concrete elements (crib walls and block walls);- Closely spaced in-situ soil-cement piles;-- Wire-mesh boxes (gabions);- Anchors into the soil or rock mass (soil nailing).

EARTH RETAINING STRUCTURE

Earth retaining structure can be classified to 2 types:

A) Externally Stabilized Systems i) In- Situ Walls

ii) Gravity Walls

B) Internally Stabilized Systems

i) Reinforced Soils

ii) In-Site Reinforcement

FUNCTION

To retain the soil at a slope that is greater than it would naturally assume, usually at a vertical or near verticalposition.

DESIGN

The designed retaining wall must be able to

ensure the following : Overturning doesn’t occur Sliding doesn’t occur The soil on which the wall rests mustn’t be

overloaded The material used in construction are not

overstressed.

DESIGN CONSIDERATION

In order to calculate the pressure exerted at

any point on the wall, the following must be

taken in account: height of water table nature & type of soil subsoil water movements type of wall material used in the construction of wall

The effect of 2 forms of earth pressure need to

be considered during the process of designing

the retaining wall that is:

a) Active Earth Pressure

“ It is the pressure that at all times are tending

to move or overturn the retaining wall”

b) Passive Earth Pressure

“It is reactionary pressures that will react in

the form of a resistance to movement of the wall.

ACTIVE EARTH PRESSURE

It is composed of the earth wedge being retained

together with any hydrostatic pressure caused by

the presence of groundwater.

This pressure can be reduced by:

i) The use of subsoil drainage behind the wall

ii) Inserting drainage openings called weep holes through the thickness of the stem to enable the water to drain away.

PASSIVE EARTH PRESSURE

• This pressure build up in front of the toe to resist the movement of the wall if it tries to move forward.

• This pressure can be increased by enlarging the depth of the toe or by forming a rib on the underside of the base.

GRAVITY WALL

There are many types of gravity wall such as

the followings:

a) Massive Gravity Wall

b) Crib Wall

c) Cantilever Gravity Wall

GRAVITY WALL

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cobbles

cement mortarplain concrete or stone masonry

They rely on their self weight to support the backfillThey rely on their self weight to support the backfill

It’s construction only need simple materials

and moderately skilled labor But the required volume of material is very

large because there’s steel reinforcement is

used. Even though it need moderately skilled

labor but the construction process is very

labor extensive.

MASSIVE GRAVITY WALL

Often made of mortared stones, masonry or

reinforced concrete It resist the lateral forces from the backfill

by virtue of their large mass These walls are very thick, so the flexural

stresses are minimal and no reinforcement

is needed.

CRIB WALL

Another type of gravity retaining structure It consists of precast concrete members

linked together to form a cribThe zone between the member is filled with

compacted soil

CRIB WALL

CANTILEVER GRAVITY WALL

TOE

HEEL

SOIL

REINFORCED CONCRETE FOOTING

REINFORCINGSTEEL

12 IN. WIDE CONCRETE

BLOCK

8 IN WIDE CONCRETE

BLOCKS

Large Flexural Stresses At Base Of Stem

STEM

CANTILEVER GRAVITY WALL It is a refinement of the massive gravity wall concept These wall have much thinner stem and utilize the weight of the

backfill soil to provide most of the resistance to sliding and overturning These walls require much less construction material because the cross

section of this wall is much smaller.

It have a large flexural stresses which requires the use of reinforced concrete or reinforced masonry

It must be carefully constructed & requires skillful labor less expensive than mass gravity walls most common type of earth retaining structure.

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They act like vertical cantilever, fixed to the ground

They act like vertical cantilever, fixed to the ground

Reinforced; smaller section

than gravity walls

COUNTERFORT WALL

GABION WALL

IN-SITU WALL

Different from gravity walls There are many types of In-Situ wall such

as the followings:

a) Sheet Pile Walls

b) Soldier Pile Walls

c) Slurry Pile Walls

SHEET PILE WALLS

Sheet piles are tine, wide steel piles Driven to the ground using pile hammer Series of sheet piles in a row form a sheet pile wall It’s usually necessary to provide lateral support at 1 or more levels above

the ground that can be done using 2 ways that is internal braces or tieback anchor.

Tieback Anchors are tension members drilled into the ground behind the wall

The most common type is a grouted anchor with a steel tendon.

• Wall With Tieback Anchors

SHEET PILE WALL

WALERGROUTED TIEBACKANCHOR

SOIL

SHEET PILES

SHEET PILE WALLS

SOLDIER PILE WALLS

Consist of a vertical wide flange steel members with horizontal timber lagging.

Often used as temporary retaining structures for construction excavation

SLURRY WALLS

It’s a cast-in-place concrete walls built using

betonies slurry The contractor digs a trench along the proposed

wall alignment and keeps it open using the slurry The reinforcing steel is inserted and the concrete

is placed using pumps.

As the concrete fills the trench, slurry exits at the

ground surface.

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Retaining Walls - Applications

Road

Train

Metros and Subways

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Retaining Walls - Applications

highway

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Retaining Walls - Applications

basement wall

High-rise building

Advances in retaining wall

Reinforced Retaining Walls• Sometimes the complexity or wall height required for certain

installations require retaining walls that are reinforced by either geofabric material or, in really tough cases, concrete filled doubleskin layers of blocks

Geosynthetic Reinforced Soil Segmental Retaining Walls

• Geosynthetic reinforced soil segmental retaining walls utilize reinforcing sheets of geogrid or suitable woven geotextile which are attached to the fascia and are embedded in a body of engineered fill.

• The integrated nature of the fascia and the abutting large body of reinforced soil thereby supports the applied earth forces. In this case the 'gravity' component of the retaining wall is provided by the reinforced soil mass acting as a monolithic unit.