RETAINING WALLS

Retaining Walls Walls built to resist the pressure of liquids,

earth filling, sand or other granular materials filled behind it after it is built.

commonly required in the construction of hill roads, dams, abutments and wing walls of bridges.

Wall may be constructed of dry stone masonry, stone masonry,brick or concrete, depending on the type of material to be retained, site conditions and height of wall.

Design Principles Basically concerned with the lateral pressure of the retained

soil and any subsoil water.

Designed to ensure that Overturning does not occur Sliding does not occur Soil on which wall rests is not overloaded Materials used in construction is not overloaded.

Factors that can cause the collapse of retaining walls:

Presence of water at rear of retaining wall which adds to the pressure exerted by soil. Soil on which wall rests is overloaded Materials used in construction are overloaded. Unsuitability of design of retaining wall

Preventive measures that can be done:

Water at rear of retaining wall need to be removed efficiently. Proper design of retaining wall is important so as to ensure soil and materials used are not overloaded Avoid any earthworks done on site where earth is retained.

Types Of Retaining Walls

Mass Retaining Wall Cantilever Retaining Wall

Large toe Large heel

Counterfort Retaining Wall

Precast Retaining Wall

1.Mass Retaining Wall

Sometimes called gravity retaining wall Economic to height of 1.8 m Can be constructed of semi engineering bricks or mass

concrete Natural stone suitable for height up to 1 m high but

generally used as facing materials for walls 1 m high and above

Diagram of Mass Retaining Wall

2. Cantilever Retaining Wall

2 forms – Large heel - offers better resistance to overturning as

base is projecting partly in front and partly behind the wall.

large toe - design is adopted when it is not possible to excavate behind wall.

Usually of reinforced concrete and works on the

principle of leverage Has economic height range of 1.2 m to 6 m

Diagram of Cantilever Retaining Wall Large Heel Large Toe

3. Counterfort Retaining Wall (also known as Buttress Retaining Wall)

Can be constructed of reinforced and prestressed concrete

Suitable for walls of height over 4.5 m Counterforts are triangular beams placed at suitable

centres behind the stem and above the base Termed as buttress if the counterforts are placed in

front exposed to view

Diagram of Counterfort Retaining Wall.

4. Precast Retaining Wall

Manufactured from high grade precast concrete Erected as permanent retaining wall or free standing

to act as dividing wall Advantages

Reduction in construction time since curing period is eliminated

Costly formwork can be eliminated Time required to erect and dismantle formwork

can be eliminated

Diagram of Precast Retaining Wall1. Anda-Crib precast retaining wall

2. Marley precast retaining wall

Importance Of Drainage At Retaining Wall Necessary since water will

cause pressure at rear of wall Water will reduce strength of

soil Water will reduce frictional

force between base and soil thus reduces strength of wall

There are 2 methods of drainage

subsoil drain behind wall Weep holes in wall and

drainage channel at front of wall

Drainage At Retaining Wall

WEEP HOLES

WEEP HOLES

DRAINAGE CHANNEL

Drainage At Retaining Wall

Thank You Hope you have enjoyed the

lecture