Application of Geosynthetics: Retaining walls, Slopes, Roads and Erosion control
Dr. A. K. Choudhary
Associate Professor & Ex-Head
Department of Civil Engineering
E-mail: [email protected]
N.I.T. Jamshedpur - 831014
3/31/2020 Prof.A.K.Choudhary
Retaining Walls
A geosynthetic-reinforced retaining wall has three
basic components:
Backfill
Reinforcement layers
Facing element
Fig.: A geosynthetic-reinforced soil retaining wall
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Role of Geosynthetic Layers in Retaining Walls
A geosynthetic layer mainly serves reinforcement function.
It resists the lateral earth pressure and thus maintains the
stability of the backfills.
Its presence also causes reduction in the load-carrying
requirements of the wall-facing elements resulting in material
and time savings.
Filtration and drainage are secondary functions to be served by
the geosynthetic in retaining walls.
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Retaining wall
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Retaining wall
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Role of Geosynthetics in Embankments Over Soft Ground
Reinforcement – results in
temporary increase in the
factor of safety
Drainage – results in increase
in the rate of consolidation to
have stable staged
construction
Separation/filtration – helps
in maintaining the integrity of
the dissimilar materials
Fig.: Embankments on weak foundation soils
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Reinforced Foundation Soil
Provides improved load-bearing capacity and reduced settlements by distributing the imposed loads over a wider area of weak subsoil.
The improved performance of a geosynthetic-reinforced foundation soil can be attributed to an increase in shear strength of the foundation soil from the inclusion of the geosynthetic layer(s). Fig.: A footing resting on the reinforced
foundation 3/31/2020 Prof.A.K.Choudhary
Fig.: A bridge abutment resting on the reinforced foundation
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Role of Geosynthetics in Roads Roads may be either Unpaved (without a permanent hard
surfacing) or Paved ( with a permanent hard surfacing)
Functions of Geosynthetics inUnpaved Road •Reinforcement–primary, if subgrade is weak. •Separation – primary, if subgrade is stiff . Improvement Caused by Geosynthetic Layer •For a given thickness of granular layer, the traffic can be increased, or •For the same traffic, the thickness of granular layer can be reduced, in comparison with the required thickness when no geosynthetic layer is used.
Fig.: A typical cross-section of the geosynthetic- reinforced unpaved road
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Functions of Geosynthetics in Paved Road
Fluid barrier (if impregnated with
bitumen, that is asphalt cement),
protecting the underlying layers
from degradation due to
infiltration of road-surface
moisture; and
Cushion, that is, stress-relieving
layer for the overlays, retarding
and controlling some common
types of cracking, including
reflective cracking.
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Fig.: A typical cross-section of the geosynthetic-reinforced unpaved road 3/31/2020 Prof.A.K.Choudhary
Benefits of Paving Fabric/Geosynthetic interlayer
Waterproofing the pavement;
Delaying the appearance of reflective cracks;
Lengthening the useful life of the overlay;
Added resistance to fatigue cracking; and
Saving up to 50 mm of overlay thickness.
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Unpaved and paved roads
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Functions of Geosynthetics in Railway Track
Separation, in new railway tracks, between soil subgrade and new ballast
Separation, in rehabilitated railway tracks, between old contaminated ballast and new clean ballast
Filtration of soil pore water rising from the soil subgrade beneath the geosynthetic, due to rising water conditions or the dynamic pumping action of the wheel loadings, across the plane of the geosynthetic;
Lateral confinement-type reinforcement in order to contain the overlying ballast stone
Lateral drainage of water entering from above or below the geosynthetic within its plane leading to side drainage ditches
Fig.: Components of the railway track structure
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Fig.: A typical drainage system in railway track
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Fig.: Applications of (a) geotextile filter, and (b) drainage geocomposite
Filtration
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Fig.: A typical cross-section of the earth dam with geotextile filters
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Advantages of Geotextile Filters
Geotextile filters provide easier and more economical
placement/installation.
Continuity of the filter medium is assured whether the
construction is below or above water level.
Quality control can be ensured more easily for geotextile-
filter systems.
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Erosion Control
The problem of soil movement due to erosive forces by moving water and/or wind as well as by seeping water is called soil erosion.
Geosynthetics in the form of nets or meshes protect the soil surface from water and wind erosion while accelerating vegetative development.
Fig.: Erosion control using geosynthetic mat and geotextile along with vegetation 3/31/2020 Prof.A.K.Choudhary
Slope Stabilization
The slope stabilization methods generally reduce
driving forces, increase resisting forces, or both.
Geosynthetic reinforcement materials has brought a
new dimension of efficiency to stabilize the unstable
and failed slopes by constructing various forms of
structures, such as reinforced slopes, retaining walls,
etc. due to mainly their corrosive resistance and long-
term stability.
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Fig.: Role of reinforcement in slopes: (a) increase factor of safety; and (b) stabilize steepened portion of slope
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Containment Facilities
Facilities containing solids such as landfills, waste piles, and ore leach pads
facilities containing liquids such as canals, reservoirs, dams
facilities containing mostly liquids at the beginning of operations and mostly solids at the end, such as settling ponds, evaporation ponds and sludge ponds.
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Fig.: Schematic diagram of a municipal solid waste landfill containment system 3/31/2020 Prof.A.K.Choudhary
Fig.: A typical cross-section of the liquid pond/reservoir
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Fig.: A typical cross-section of the canal
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Tunnels
Geotextiles and geomembranes are commonly used in the
modern-day tunnel technology to construct waterproof tunnels.
Fig.: Cross-section of a tunnel vault showing general arrangementof the lining system
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Laying of geogrid
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Geocell retaining wall
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A view of Reinforced Earth Slope
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Placing of fill material over geogrid
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Four laning work on NH-6 (Dankuni to Kolaghat)
Water logged area
(soft ground conditions)
Compaction of fly ash over layer of geotextile
Length of stretch – 54 km
Height of embankment – 3 to
4 m
Fly ash utilisation – 2 Million
cubic metres
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Sarita Vihar flyover reinforced approach embankment
Arrangement of friction ties before laying pond
ash
Laying of friction ties
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Compaction using plate vibrator near
the facing panels
Compaction of pond ash using static and vibratory rollers
Sarita Vihar flyover reinforced approach embankment
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THANK YOU
3/31/2020 Prof.A.K.Choudhary
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