Retaining walls are structures designed to hold back earth and materials from sliding and are used when there is a need to hold earth or other materials in a vertical position. There are different types of retaining walls including gravity, cantilever, counterfort, buttress, basement/foundation walls, and bridge abutments. Stability is analyzed using various methods such as the method of slices, Bishop's method, Sarma method, and Lorimer's method. Reinforced earth uses geosynthetic materials like geogrids and geocells to reinforce soil and is commonly used in retaining walls.

1. RETAINING
WALLS
-TAIYABA RASHID
F/O ARCHITECTURE & EKISTICS
JAMIA MILLIA ISLAMIA
NEW DELHI
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RETAINING WALLS
• Retaining walls are used to retain
earth or other materials which have
the tendency to slide and repose at
a particular inclination.
• They provide lateral support to the
earthfill, embankment or other
materials in order to hold them in a
vertical position.
• Types:
Gravity retaining wall
Cantilever retaining wall
Counterfort retaining wall
Buttress retaining wall
Basement/foundation wall
Bridge abutment

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GRAVITY RETAINING WALL
• Made of plain concrete or brick masonry.
• Stability of wall is maintained by its weight.
• Generally made up to a height of 3m of wall.

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CANTILEVER RETAINING WALL
• Consists of a vertical wall, heal
slab & toe slab which act as
cantilever beams.
• Stability maintained by weight of
retaining wall & weight of earth
on the base of retaining wall.
• Height ranges from 3m to 8m.

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COUNTERFORT RETAINING WALL
• Height ranges from 6m to 8m.
• More economical to tie the vertical wall with the heel slab by counterforts at
some spacing.
• Acts as tension member to support vertical wall & reduces bending moment.
• Supports the heel slab & reduces bending moment.
• Spacing: 1/3rd the height of wall.
• Stability maintained by weight of earth on base & by self-weight.
• More widely used as it is hidden beneath the retained materials.
• Has a clean, uncluttered face for more efficient use of space in front of wall.

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COUNTERFORT RETAINING WALL

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BUTTRESS RETAINING WALL
• Similar to the counterfort wall.
• Vertical wall is tied with toe of retaining wall at some spacing.
• Acts as compression member to support vertical wall & reduces its bending
moment.
• Supports toe slab & reduces its bending moment.
• Spacing: 1/3rd the height of the wall.
• Buttress as compression member is more economical than a tension
counterfort.

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BUTTRESS RETAINING WALL

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BASEMENT/FOUNDATION WALL
• Restrained at the bottom by
basement floor slab & at the top by
the first floor slab.
• Subjected to:
Lateral earth pressure exerted by
earth fill
Vertical load from superstructure.
• Lateral support is provided by
basement floor & first floor slabs.

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BRIDGE ABUTMENT
• Behaviour similar to basement or
foundation wall.
• Superstructure induces horizontal &
vertical loads that alter the normal
cantilever behaviour.

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BRIDGE TERMINOLOGY

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FORCES ON RETAINING WALLS
• Self-weight
• Weight of soil above foundation base
• Earth pressure
• Surcharge i.e., forces due to loads on earth surface
• Soil reactions on footing
• Friction on footing due to sliding

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CONSTRUCTION METHODS
• A concrete retaining
wall
• An interlocking block
retaining wall
• A Wood retaining wall
• An Insulated Concrete
Form retaining wall or
ICF retaining wall

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SLOPE STABILITY
• The field of slope stability encompasses the analysis of static and dynamic
stability of slopes of earth and rock-fill dams, slopes of other types of
embankments, excavated slopes, and natural slopes in soil and soft rock.
SIMPLE SLOPE SLIP SECTION
SLOPE WITH ERODING RIVER & SWIMMING
POOL

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SLOPE STABILITY
• If the forces available to resist movement are
greater than the forces driving movement, the
slope is considered stable.
• Factor of safety=Forces resisting movement /Forces
driving movement.
• In earthquake-prone areas, the analysis is typically
run for static conditions and pseudo-static
conditions, where the seismic forces from an
earthquake are assumed to add static loads to the
analysis.
• METHOD OF SLICES
• BISHOP’S METHOD
• SARMA METHOD
• LORIMER'S METHOD

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METHOD OF SLICES
SLOPE STABILITY-ANALYSIS
METHODS
• Method for analysing the stability of a slope in two dimensions.
• The sliding mass above the failure surface is divided into a number of slices.
• The forces acting on each slice are obtained by considering the mechanical
equilibrium for the slices.

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BISHOP’S METHOD
SLOPE STABILITY-ANALYSIS
METHODS
• Proposed by Alan W. Bishop.
• Method for calculating the stability of slopes.
• An extension of the Method of Slices.
• By making some simplifying assumptions, the problem becomes statically
determinate and suitable for hand calculations.
• Forces on the sides of each slice are horizontal
• The method has been shown to produce factor of safety values within a few
percent of the "correct" values.

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BISHOP’S METHOD
SLOPE STABILITY-ANALYSIS
METHODS
• c’= effective cohesion
• ’= angle of internal friction
• b= width of slice
• w= weight of each slice
• u= water pressure at base of each slice

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SARMA METHOD
SLOPE STABILITY-ANALYSIS
METHODS
• Proposed by Sarawa K. Sarma
• A Limit equilibrium technique used to assess the stability of slopes under
seismic conditions.
• May also be used for static conditions if the value of the horizontal load is
taken as zero.
• Can analyse a wide range of slope failures as it may accommodate a multiwedge failure mechanism and therefore it is not restricted to planar or
circular failure surfaces.
• May provide information about the factor of safety or about the critical
acceleration required to cause collapse.

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LORIMER'S METHOD
SLOPE STABILITY-ANALYSIS
METHODS
• Developed in the 1930s by Gerhardt
Lorimer.
• A technique for evaluating slope stability
in cohesive soils.
• Differs from Bishop's Method in that it uses
a clothoid slip surface in place of a
circle.
• This mode of failure was determined
experimentally to account for effects of
particle cementation.
A CLOTHOID OR EULER SPIRAL

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REINFORCED EARTH
• Also called Mechanically Stabilized
Earth or MSE.
• Soil constructed with artificial
reinforcing.
• Can be used for retaining
walls, bridge abutments, dams, sea
walls, and dikes.

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REINFORCED EARTH
• MSE walls stabilize unstable slopes and retain the soil on steep slopes and
under crest loads.
• The wall face is often of precast, segmental blocks, panels or geocells that
can tolerate some differential movement.
• The walls are infilled with granular soil, with or without reinforcement, while
retaining the backfill soil.
• Reinforced walls utilize horizontal layers typically of geogrids.
• The reinforced soil mass, along with the facing, forms the wall.
• In many types of MSE’s, each vertical fascia row is inset, thereby providing
individual cells that can be infilled with topsoil and planted with vegetation
to create a green wall.

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ADVANTAGES
REINFORCED EARTH
• Ease of installation.
• Quick construction.
• Do not require formwork or curing and each
layer is structurally sound as it is
laid, reducing the need for
support, scaffolding or cranes.
• Do not require additional work on the
facing.
• Retain sufficient flexibility to withstand large
deformations without loss of structural
integrity, and have high seismic load
resistance.

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GEOSYNTHETIC MATERIALS
• Polymeric products used to solve civil
engineering problems.
• Includes eight main product categories:
geotextiles, geogrids, geonets, geomembranes,
geosynthetic clay
liners, geofoam, geocells and geocomposites.
• Suitable for use in the ground where high levels
of durability are required.
• Can also be used in exposed applications.
• Available in a wide range of forms and
materials, each to suit a slightly different end
use.
Geocells

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GEOSYNTHETIC MATERIALS
GEOSYNTHETIC REINFORCED STRUCTURES

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GEOGRID
• Geosynthetic material used to reinforce soils.
• Used to reinforce retaining walls, as well as
subbases or subsoils below roads or structures.
• Soil pulls apart under tension. Compared to
soil, geogrids are strong in tension.
• Transfer forces to a larger area of soil.
• Made of polymer materials, such
as polyester, polyethylene or polyproylene.
• Woven or knitted from yarns, heat-welded from
strips of material, or produced by punching a
regular pattern of holes in sheets of
material, then stretched into a grid.

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• Also called Cellular Confinement Systems.
• Used in construction for erosion
control, soil stabilization on flat ground and
steep slopes, channel protection, and
structural reinforcement for load support
and earth retention.
• Typically made with ultrasonicallywelded high-density polyethylene (HDPE)
or Novel Polymeric Alloy strips that are
expanded on-site.
• Creates a stiff mattress or slab to distribute
the load over a wider area.
• Reduces punching of soft soil.
• Increases shear resistance and bearing
capacity.
• Decreases deformation.
GEOCELLS

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