Application of Geosynthetics: Retaining walls, Slopes, Roads and Erosion...

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


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.


Retaining wall


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


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


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


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.


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.


Unpaved and paved roads


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


Fig.: A typical drainage system in railway track


Fig.: Applications of (a) geotextile filter, and (b) drainage geocomposite

Filtration


Fig.: A typical cross-section of the earth dam with geotextile filters


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.


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.


Fig.: Role of reinforcement in slopes: (a) increase factor of safety; and (b) stabilize steepened portion of slope


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.


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


Fig.: A typical cross-section of the canal


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


Laying of geogrid


Geocell retaining wall


A view of Reinforced Earth Slope


Placing of fill material over geogrid


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


Sarita Vihar flyover reinforced approach embankment

Arrangement of friction ties before laying pond

ash

Laying of friction ties


Compaction using plate vibrator near

the facing panels

Compaction of pond ash using static and vibratory rollers

Sarita Vihar flyover reinforced approach embankment


THANK YOU


Application of Geosynthetics: Retaining walls, Slopes, Roads and Erosion...

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