1. ERT352 FARM STRUCTURES RETAINING WALL DESIGN
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2. INTRODUCTION
Retaining walls are used to retain earth or other material in a vertical or nearly vertical position at location where an abrupt change in ground level occurs.
This caused the retained earth to exert a lateral pressure on the wall, thereby tending to overturn, side and settle the retaining wall.
Failure of retaining wall as shown in figure below.

3. TYPE OF RETAINING WALLS
There are many types of retaining structures and generally divided into two main categories namely gravity wall and cantilever wall.
The following are some commonly used walls in Malaysia
Gravity wall
Depends on its own weight to provide
the necessary stability
Usually constructed of plain concrete
or stone masonry
Height of wall < 3 m

4. TYPE OF RETAINING WALLS (cont.)
Cantilever wall
Most common type of retaining structures
Economical for height up to 8 m
Consists of a vertical cantilever spanning from a large rigid base slab
Counterfort wall
Used where the overall height of wall is too large to be constructed economically as cantilever
The wall and base are tied together at intervals by counterfort or bracing walls
Economical for high of walls above m backfill
Butrress wall
Similar to counterfort wall but the bracing is constructed in front of the wall.
Provides free usable space in front of the wall

5. TYPE OF RETAINING WALLS (cont.)
Gabion wall
Made of rectangular containers (basket) which are filled with stone and stacked on one other.
Can conform to ground movement, dissipate energy from flowing water and drain freely
Crib wall
Constructed by interlocking individual boxes made from timber or pre-cast concrete members.
The boxes filled with crushed stone or other coarse granular materials.
Tie back
A horizontal wire or rod or helical anchor used to reinforce retaining walls for stability
Resists forces that would cause the wall lean
Keystone
Made up from concrete segmental block units
Using interlocking systems
Offers aesthetic appeal, cost efficiency, easy installation and strength.

6. ANALYSIS AND DESIGN
The design of RC retaining wall can be divided into two fundamental stages as follow:
Stability analysis
Lateral force due to earth pressure constitutes the main force acting on the retaining wall, tending to make it overturn, slide and settle.
Element design and detailing
3 elements of retaining wall (eg.: stem, toe slab and heel slab) are designed as cantilever slabs to resist the designed moments and shear forces.

7. Safety factor for stability analysis

8. Example:
Design a cantilever wall to retain earth with horizontal backfill which subjected to surcharge of 10 kN/m2. the top of the wall is 4.0 m above the ground level and foundation depth may be taken as 0.9 m below ground level with a safe bearing capacity 170 kN/m2. Assume the backfill has a unit weight of 19 kN/m3 and an angle of shearing resistance of The coefficient of friction between soil and concrete is Use fck = 30 N/mm2, fyk = 500 kN/m2 and nominal cover = 45 mm

10. Solution:

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21. THANK YOU
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