Retaining wall - design of reinforced concrete structure

RETAINING WALL
DESIGN OF REINFORCED
CONCRETE STRUCTURE

-: CREATED BY:-
KAVIN RAVAL
141080106026
-: SUBMITED TO:-
PROF. VIVEK LOLARIYA
CIVIL DEPARTMENT
ACET

CONTENT
• INTRODUCTION
• STABILITY CONDITIONS
• COMPONENTS OF WALL

RETAINING WALL
• Retaining wall is a structure 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 collapse into a more natural shape.

Types of retaining wall
• Gravity wall
• Made of plain concrete or brick masonry
• The stability of the wall is maintained by its own weight
• made up to a height of 3 m.

• Cantilever Retaining wall
• It consists of a vertical wall called stem, heel slab and toe
slab.
• All elements of behave like cantilever beam of slab. Hence
it is called cantilever retaining wall.
• The stability is maintained by the weight of the retaining
wall and the earth on the heel slab of the retaining wall.
• Suitable upto 6 m.
• It may be T-shaped or L-shaped

Cantilever Retaining wall

• Counterfort retaining wall
• In this wall heel slab and stem are connected by counterfort.
• Because of provision of counterforts, the vertical stem and heel
slab acts as a continuous slab.
• The counterfort acts as a tension member to support the stem
and reduces bending moment.
• The stability is maintained by the self weight of wall and by the
weight of earth on the base slab.
• Suitable and economical for height more than 6 to 8 m.

Counterfort retaining wall

• Bridge abutment
• Similar as cantilever wall, but top of stem is braced by the deck slab of bridge.
• The stem can be design as fixed at base and simply supported. (Propped
cantilever)

• Box culvert
• It acts as closed rigid frame.
• It consist of either single or multiple cells.
• It resists lateral pressure of earth and vehicle load.

• Sheet pile wall
• Used to build continuous walls for waterfront structures and for temporary
construction wall heights > 6 m if used with anchors.
• Can be made of steel, plastics, wood, pre-cast concrete.

• Gabbion wall
• Gabbions are multi-celled, welded wire or rectangular wire
mesh boxes, which are then rockfilled.

STABILITY CONDITIONS
CHAPTER - 2

Stability Requirement of retaining wall
1. Stability against overturning (Cl.20.1, P: 33 )
It means factor of safety against overturning should be
more than or equal to 1.55

2. Stability against sliding (Cl.20.2, P: 33 )
It means factor of safety against sliding should be more
than or equal to 1.55

3. Stability against maximum pressure at the base
( stability against settlement)
If the maximum pressure at base less than safe bearing
capacity of soil, the wall is stable against settlement.
Max. Pressure
SBC of soil

4. No tension at base
If the minimum pressure at base is greater than or equal to zero than,
the wall is not under tension.
Min. Pressure,

COMPONENTS OF WALL
CHAPTER - 3

COMPONENTS OF RETAINING WALL
BACKFILL
HEEL
SHEAR KEY
TOE
STEM
FRONT

STEM
• Vertical stem in cantilever retaining wall resists earth pressure
from backfill side and bends like a cantilever.
• The thickness of cantilever slab is larger at the base of stem and
it decreases gradually upwards due to reduction of soil pressure
with decrease in depth.

BASE SLAB
• The base slab form the foundation of the retaining wall. It
consists of a heel slab and the toe slab.
• The heel slab acts as a horizontal cantilever under the combined
action of the weight of the retaining earth from the top and the
soil pressure acting from the soffit.
• The toe slab also acts as a cantilever under the action of the soil
pressure acting upward.
• The stability of the wall is maintained by the weight of the earth
fill and on the heel slab together with the self-weight of the
structural elements of the retaining wall.
• Cantilever type retaining walls are suitable upto 5m depth of
backfill.

SHEAR KEY
• The main purpose of installation of shear keys is to increase the extra
passive resistance developed by the height of shear keys.
• However, active pressure developed by shear keys also increases
simultaneously.
• The success of shear keys lies in the fact that the increase of passive
pressure exceeds the increase in active pressure, resulting in a net
improvement of sliding resistance.
• On the other hand, friction between the wall base and the foundation
soils is normally about a fraction of the angle of internal resistance (i.e.
about 0.8p ) where p is the angle of internal friction of foundation soil.
• When a shear key is installed at the base of the retaining wall, the
failure surface is changed from the wall base/soil horizontal plane to a
plane within foundation soil.
• Therefore, the friction angle mobilized in this case is p instead of 0.8p
in the previous case and the sliding resistance can be enhanced.

BACKFILL
• Second, a retaining wall must have properly compacted backfill.
Backfill refers to the dirt behind the wall.
• In order to provide proper drainage, at least 12 inches of granular
backfill (gravel or a similar aggregate) should be installed directly
behind the wall.
• Compacted native soil can be used to backfill the rest of the space
behind the wall. If you intend to do landscaping behind the wall, a
6+ inch layer of native soil should also be placed over the gravel
fill.

Retaining wall - design of reinforced concrete structure

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