BNT20903 :
RAILWAY
INFRASTRUCTURE AND
FACILITIES
> Retaining Wall for Railway
Project
By
Ir. Muhamad Faiz bin Abd Latif
Lecturer
FTK, UTHM (Kampus Pagoh)
Design & Construction of Retaining
Wall for Railway Project
• Introduction
• Types of Retaining Walls
• Analysis & Design
1. Stability Analysis
Introduction
• Retaining wall is used to retain earth or other material
in vertical (or nearly vertical) position at locations
where an abrupt change in ground level occurs.
• Prevent the retained earth from assuming its natural
angle of repose
• The retained earth exerts lateral pressure on the
wall – overturn, slide & settlement
• The wall must be design to be stable under the
effects of lateral pressure
Introduction
Overturning
Sliding
Settlement
Failure in Retaining Wall
Types of Retaining Walls
Gravity Wall
• Depends entirely on its own
weight to provide necessary
stability.
• Usually constructed of plain
concrete or stone masonry.
• Plain concrete gravity wall –
height < 3 m.
• In designing this wall, must keep
the thrust line within the middle
third of the base width – no
tensile stress to be developed.
Types of Retaining Walls
Cantiliver Wall
• Economical for height of up to
8m.
• Structure consist of a vertical
cantilever spanning from a large
rigid base slab.
• Stability is maintained essentially
by the weight of the soil on the
base slab + self weight of
structure.
Large rigid base
Types of Retaining Walls
Counterfort Wall
• When the overall height of the
wall is too large to be constructed
economically as a cantilever.
• Wall & base are tied together at
intervals by counterfort or
bracing walls.
• Bracing in tension.
• Economical for high wall usually
above 6 – 7 m of backfill.
Types of Retaining Walls
Buttress Wall
• Similar to counterfort wall,
but bracing is constructed
in front of the wall.
• Bracing in compression.
• More efficient than
counterforts, but no usable
space in front of the wall.
Types of Retaining Walls
Gabion Wall
• Made of rectangular containers.
• Fabricated of heavily galvanized
wire, filled with stone and stacked
on one another, usually in tiers
that step back with the slope.
• Advantages: conform to ground
movement, dissipate energy from
flowing water & drain-freely.
Types of Retaining Walls
Crib Wall
• Interlocking individual boxes
made from timber or precast
concrete members.
• Boxes are filled with crushed
stone or other granular materials
to create free-draining structure.
Types of Retaining Walls
Tieback Wall
• Tieback is a horizontal wire or rod,
or a helical anchor use to reinforce
retaining wall for stability.
• One end of the tieback is secured to
the wall, while the other end is
anchored to a stable structure i.e.
concrete deadman driven into the
ground or anchored into the earth
with sufficient resistance.
• Tieback-deadman structure resists
forces that will cause the wall to
lean.
Types of Retaining Walls
Keystone Wall
• Made up of segmental block units,
made to last.
• Based around a system with
interlocking fibreglass pins
connecting the wall unit and soil
reinforcement.
• Combination of these resulted in a
strong, stable and durable wall
system.
• Offers aesthetic appeal, cost
efficiency, easy installation &
strength.
Analysis & Design
Stability Section
Analysis Design
Overturn, Slide
Moment Design
& Settle
Stability check
under ultimate
Check for Shear
limit state: EQU,
STR & GEO
Stability Analysis - Overturning
• Occurs because of unbalanced moment.
• When overturning moment about toe to due lateral
pressure >> resisting moment of self weight of wall &
weight of soil above the heel slab.
• Critical condition occur when maximum horizontal
force acts with minimum vertical load.
ɤf = 0.9 applied to the permanent vertical load, ƩVk,
which is “favourable”
ɤf = 1.1 applied to the permanent earth loading, Hk at
rear face of the wall, which is “unfavourable”
ɤf = 1.5 applied to variable surcharge loading (if any),
which is “unfavourable”
Stability Analysis - Overturning
Stability Analysis - Sliding
• Resistance against sliding provided by friction
between the bottom surface of the base slab and soil
beneath.
• Resistance provided by passive earth pressure on
the front face of the base gives some contribution
(often ignored because it is often backfilled).
ɤf = 1.0 applied to the permanent vertical load, ƩVk,
which is “favourable”
ɤf = 1.35 applied to the permanent earth loading,
Hk at rear face of the wall, which is “unfavourable”
ɤf = 1.5 applied to variable surcharge loading (if
any), which is “unfavourable”
Stability Analysis - Sliding
Stability Analysis – Settlement
• Width of base slab must be adequate to distribute
the vertical force to the foundation soil.
• To determine the required size of base, bearing
pressure underneath is assessed on the basis of the
ultimate limit state (GEO).
• Since the base slab of the wall is subjected to the
combined effects of an eccentric vertical coupled with
an overturning moment, the analysis is similar to that
of foundation design.
Stability Analysis - Settlement
Element Design & Detailing
Element Design & Detailing
• Three elements of retaining wall: Stem, Toe slab & Heel slab are
designed as cantilever slab.
• Stem: Designed to resist moment caused by force γfHk (γf = load
combination)
• Toe Slab: Net pressure is obtained by deducting the weight of
concrete in the toe slab from upward acting soil pressure.
• Heel slab: Designed to resist moment due to downward pressure
from the weight of retained earth (plus surcharge, if any) and
concrete slab.
• Safety factor γf1, γØ2, and γf3 should be considered to provide a
combination which gives the critical design conditions (worst
combination of 1 & 2.
Example 1
Cantilever Reinforced
Concrete (RC)
Retaining Wall
Example 1: Cantilever Reinforced
Concrete (RC) Retaining Wall
Example 1: Cantilever Reinforced
Concrete (RC) Retaining Wall
Suggest Suitable Dimensions for the RC Retaining Wall
Example 1: Cantilever Reinforced
Concrete (RC) Retaining Wall
Calculate the Active Soil Pressure, P
Example 1: Cantilever Reinforced
Concrete (RC) Retaining Wall
Taking Moment at Point A
A
Example 1: Cantilever Reinforced
Concrete (RC) Retaining Wall
Stability Analysis
Example 1: Cantilever Reinforced
Concrete (RC) Retaining Wall
Stability Analysis (Continued)
Example 1: Cantilever Reinforced
Concrete (RC) Retaining Wall
Stability Analysis (Continued)
Example 1: Cantilever Reinforced
Concrete (RC) Retaining Wall
Stability Analysis (Continued)
Example 1: Cantilever Reinforced
Concrete (RC) Retaining Wall
Stability Analysis (Continued)
m4
Example 1: Cantilever Reinforced
Concrete (RC) Retaining Wall
Element Design
Thank You
