Acknowledgement

It’s indeed my immense pleasure to wish my deep sense of gratitude to our teaching faculty who relentlessly tried to get the best out of me. It is because of their valuable guidance and continuous encouragement without which this milestone would not have been a success.I would like to express my sincere gratitude to Prof. S.S. Patil H.O.D. of Civil EngineeringFor his excellent guidance and cooperation throughout.

I would like to express my sincere gratitude to Prof. Ashok Kumar Rajanavar, Prof.M.G. Kalyanshetti for excellent guidance and encouragement throughout the project.

Finally, I would like to express my heart-felt gratitude to my parents, friends andFaculty of the department who have helped us either directly or indirectly for Successful completion of this project.

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Contents

1. INTRODUCTION..............................................................................................................4

2. GEOSYNTHETICS............................................................................................................5

2.1 Functions of geosynthetics...............................................................................................5

2.1.1 Separation:.................................................................................................................5

2.1.2 Filtration:...................................................................................................................6

2.1.3Reinforcement.............................................................................................................6

2.1.4Drainage:.....................................................................................................................6

2.1.5 Erosion control:..........................................................................................................6

2.1.6 Barrier (Sealing) Function:........................................................................................6

2.2 Economic importance of geosynthetics............................................................................7

2.3 Environmental importance of geotextile..........................................................................7

2.4 Standards of geosynthetics...............................................................................................7

2.5 BIS/IRC/RDSO STANDARDS ON GEOSYNTHETICS...............................................7

2.6ADVANTAGES OF GEOSYNTHETICS........................................................................8

3. Types of Geosynthetics and their applications...................................................................9

3.1 Geotextile.........................................................................................................................9

3.1.1 Types of geotextile.....................................................................................................9

3.1.2 Applications of geotextile..........................................................................................9

3.2 Geogrids...........................................................................................................................9

3.2.1 Types of Geogrids....................................................................................................10

3.2.2 Applications of Geogrids in Roads & highways.....................................................10

3.3 Geonet.............................................................................................................................10

3.3.1 Uses and Applications of geonet.............................................................................10

3.4 Geocells..........................................................................................................................10

3.4.1 Application...............................................................................................................11

3.5 Geocomposite.................................................................................................................11

3.6. Geomembrane................................................................................................................11

3.6.1 Applications of geomembrane.................................................................................11

3.7 Geosynthetic Clay Liner.................................................................................................11

3.7.1 Applications of geosynthetic clay liner...................................................................11

3.8 Geofoam.........................................................................................................................12

3.8.1 Applications of Geofoams.......................................................................................12

4.DISADVANTAGES OF GEOSYNTHETICS.....................................................................12

5. CONCLUSION....................................................................................................................12

REFERENCES.........................................................................................................................12

1. INTRODUCTIONA typical flexible pavement system includes four distinct layers: asphalt concrete,

base course, sub base, and sub grade (Fig. 1). The surface layer is typically asphalt concrete, which is a bituminous hot-mix Aggregate obtained from distillation of crude petroleum. The asphalt concrete is underlain by a layer of base course, typically consisting of 0.2 m to 0.3 m of unbound coarse aggregate. An optional subbase layer, which generally involves lower quality crushed aggregate, can be placed under the base course in order to reduce costs or to minimize

capillary action under the pavement.Pavement distress may occur due to either traffic or environmental loads. Traffic loads result from the repetition of wheel loads, which can cause either structural or functional failure. Environmental loads are induced by climatic conditions, such as variations in temperature or moisture in the subgrade, which can cause surface irregularities and structural distress. Cycles of wetting and drying (or freezing and thawing) may cause the breakdown of base course material. Construction practices also affect pavement performance. For example, the use of aggregates with excessive fines may lead to rapid pavement deterioration. Finally, pavement distress is also a function of maintenance or, more correctly, lack of maintenance (Yoder and Witczak 1975). For example, sealing cracks and joints at proper intervals and maintaining the shoulders improve pavement performance. The various distress mechanisms induced by traffic and environmental loads can be enhanced through the use of geosynthetics, as discussed next.Necessity

A large variety of detrimental factors affect the service life of roads and pavements including environmental factors, subgrade conditions, traffic loading, utility cuts, road widening, and aging. These factors contribute to an equally wide variety of pavement conditions and problems which must be addressed in the maintenance or rehabilitation of the pavements, if not dealt with during initial construction. Pavement maintenance treatments are often ineffective and short lived due to their inability to both treat the cause of the problems and renew the existing pavement condition. The main cause of distress in pavements is that they are quite permeable with 30 to 50% of precipitation surface water infiltrating through the pavement, softening and weakening the pavement subgrade and base, accelerating pavement degradation. Existing pavement distress such as surface cracks, rocking joints, and subgrade failures cause the rapid reflection of cracking up through the maintenance treatment.

Therefore, the preferred strategy for long-term road and pavement performance is to build in safeguards during initial construction. These performance safeguards include stabilizing the subgrade against moisture intrusion and associated weakening; strengthening road base aggregate without preventing efficient drainage of infiltrated water; and, as a last resort, enhancing the stress absorption and moisture-proofing capabilities of selected maintenance treatments. Geosynthetics are the most cost effective tools for roads safeguarding and pavements in these ways.

The four main applications for geosynthetics in roads are subgrade separation and stabilization, base reinforcement, overlay stress absorption, and overlay reinforcement.

Geosynthetics are also helpful in rehabilitating distressed road surfaces. The application of a layer of asphalt concrete called an overlay is often the solution for damaged pavement.

Geosynthetics can be used as interlayer by placing them below or within the overlay. Some geosynthetics relieve stress and others are able to reinforce the overlay. The products may also provide a moisture barrier.

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2. GEOSYNTHETICS

Geo-synthetics are synthetic products, where at least one of the components is made from a synthetic or natural polymer, in the form of a sheet, a strip or a three dimensional structure, non-woven, knitted, or woven which is used in contact with soil/rock and/or other materials in geotechnical and civil engineering applications.

Geosynthetics are an established family of geomaterials used in a wide variety of civilEngineering applications. Many polymers (plastics) common to everyday life are found inGeosynthetics. The most common are polyolefin and polyester; although rubber,Fibreglass and natural materials are sometimes used. Geosynthetics may be used to function as a separator, filter, planar drain, reinforcement, cushion/protection, and/or as a liquid and gas barrier. The various types of geosynthetics available, along with their specific applications, are discussed in subsequent sections.

2.1 Functions of geosyntheticsGeosynthetics include a variety of synthetic polymer materials that are specially fabricated to be used in geotechnical, geo-environmental, hydraulic and transportation engineering applications. It is convenient to identify the primary function of a geo-synthetic as being one of

separation filtration drainage reinforcement fluid/gas containment erosion control

In some cases the geo-synthetic may serve dual functions.

2.1.1 Separation: The geo-synthetic acts to

separate two layers of soil that have different particle size distributions.

When stone aggregates are placed over a subgrade consisting of fine aggregates in

In flexible pavement, there are two possible mechanisms that can take place. One is that fine soil attempts to enter into the voids of stone aggregate, thereby ruining its drainage capability; the other is that the stone aggregates attempts to intrude into the fine soil, thereby deteriorating the stone aggregate strength. This would diminish the performance of the aggregates as well as the subgrade layer. However, with the use of geotextile between these two layers will avoid these mechanisms, leading to satisfactory performance of both the stone aggregates and subgrade layer.

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2.1.2 Filtration: It is defined as ‘the equilibrium geotextile- to-soil system that allows for adequate

liquid flow with limited soil loss across the plane of the geotextile over a service lifetime compatible with the application under consideration’. The geosynthetics acts similar to a sand filter by allowing water to move through the soil while retaining all upstream soil particles.

The geotextile must also have the strength and durability to survive construction and long-term conditions for the design life of the drain. Additionally, construction methods have a critical influence on geotextile drain performance. Figure explains the filtration function of geotextile.

2.1.3ReinforcementThe geosynthetics acts as a reinforcement element within a soil mass or in

combination with the soil to produce a composite that has improved strength and deformation properties over the unreinforced soil. Reinforcement enables embankments to be constructed over very soft foundations and to build embankment side slopes at steeper angles that would be impossible with unreinforced soil. Geosynthetics (usually georgics) have also been used to bridge over voids that may develop below load bearing granular layers (roads and railways) or below cover systems in landfill applications.

Low strength fine grained silt and clay are good in compression but poor in tension. In Such case, geotextile materials which are good in tension can recover the deficiency of low strength soil.

2.1.4Drainage: The geosynthetics acts as a drain to carry fluid flows through less permeable soils. For

example, geotextile are used to dissipate pore water pressures at the base of roadway embankments. For higher flows, geocomposite drains have been developed. These materialsHave been used as pavement edge drains, slope interceptor drains, and abutment and retaining wall drains. Prefabricated vertical drains (PVDs) have been used to accelerate consolidation of soft cohesive foundation soils below embankments and preload fills. 2.1.5 Erosion control:

The geosynthetics acts to reduce soil erosion caused by rainfall impact and surface water runoff. For example, temporary geosynthetics blankets and permanent lightweight geosynthetics mats are placed over the otherwise exposed soil surface on slopes. Geotextile silt fences are used to remove suspended particles from sediment-laden runoff water. Some erosion control mats are manufactured using biodegradable wood fibres.

2.1.6 Barrier (Sealing) Function:A geotextile performs this function when impregnated with asphalt or other polymeric

mixes rendering it relatively impermeable to both cross-plane and in- plane flow. In this function geotextile is placed on the existing pavement surface following the application of an asphalt tack coat. The geotextile absorbs asphalt to become a waterproofing membrane minimizing vertical flow of water into the pavement structure.

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For example, geomembranes, thin film geotextile composites, geosynthetics clay liners (GCLs) and field-coated geotextile are used as fluid barriers to impede flow of liquid or gas.

2.2 Economic importance of geosynthetics These are commonly accepted as durable, long lasting and environmentally safe

Solutions to geotechnical engineering projects. The cost of geo-synthetics applied usually between 3 to 5 per cent of the total cost of

projects. For a number of projects, savings of 30 per cent in total project costs have been

reported. Minimizes the regular repair and maintenance costs directly. Prevent accidents, increase efficiency of structures, minimizes pollution and leads to

efficient use of natural resources.

2.3 Environmental importance of geotextile The civil engineering structures need to have long term durability to prevent potential

ecological disasters (floods, draughts, earthquakes, global warming). Geosynthetics provide such long lasting solutions with minimum cost.

Geo-techs are difficult or impossible to degrade. However, in view of their inert nature they can be disposed off without the danger of contamination.

Geosynthetics assist the environment by acting as a containing barrier for toxic materials.

The envisaged functional lifetime of geosynthetics is extremely long, in many cases over 100 years.

Geosynthetics provide sealing and capping of pollution due to chemicals released after road and rail accidents into groundwater areas.

2.4 Standards of geosynthetics American Society for Testing and Materials Standards (ASTM) International Organization for Standardization standards (ISO/TC221) Bureau of Indian standards (BIS) American Association of State Highway and Transportation Officials standards

(AASHTO) Federal Highway Administration standards (FHWA) Nordic guidelines British Standards International Geosynthetics Society standards (IGS) Geosynthetics Research Institute (GRI) Geosynthetics Materials Association (GMA) US Provincial standards Industrial Fabrics Association International (IFAI) Geo-synthetic International Erosion Control Association (IECA) European Center For Standardization (CEN)

2.5 BIS/IRC/RDSO STANDARDS ON GEOSYNTHETICS BIS standards mainly on test methods, jute & coir geotextile, PVC / HDPE

geomembranes for waterproof lining (IS 14715:2000; IS 14986:2001; IS 15869:2008; IS 15871:2009;IS 15909:2010; and IS 15910:2010 Geosynthetics for highways)

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Standards activity in IRC/RDSO is not universally acceptable and needs drastic changes to include all stakeholders.

2.6ADVANTAGES OF GEOSYNTHETICSGeosynthetics, including geotextile, geomembranes, geonets, geocomposites and

geosynthetics clay liners, often used in combination with conventional materials, offer the following advantages over traditional materials:

Space Savings Material Quality Control Construction Quality Control Cost Savings Technical Superiority Construction Timing Material Deployment Material Availability Environmental Sensitivity

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3. Types of Geosynthetics and their applicationsGeosynthetics are, used in a wide variety of applications for infrastructure projects like Roads, River & Sea Bank Protection, Canal Lining, Landfills, Airport taxiways etc.

In broad terms there are around 9 categories of Geosynthetics as follows:- Geotextile Geogrids Geonets Geocells Geomembranes Geocomposites Geofoam Geosynthetic clay liners

3.1 GeotextileAs we know, the prefix of geotextile, geo, means earth and the ‘textile’ means fabric.

Therefore, according to the definition of ASTM 4439, the geotextile is defined as follows:"A permeable geosynthetics comprised solely of textiles. Geotextile are used with

foundation, soil, rock, earth, or any other geotechnical engineering-related material as an integral part of human-made project, structure, or system."

3.1.1 Types of geotextileIn general, the vast majority of geotextile are made from polypropylene or polyester formed into fabrics as follows:

Woven monofilament Woven multifilament Woven slit-film monofilament Woven slit-film multifilament Nonwoven continuous filament heat bonded Nonwoven continuous filament needle-punched Nonwoven staple needle-punched Nonwoven resin bonded Other woven and nonwoven combinations Knitted

3.1.2 Applications of geotextileThe basic principles of incorporating geotextile into a soil mass are the same as those

utilized in the design of reinforced concrete by incorporating steel bars. The fabrics are used to provide tensile strength in the earth mass in locations where shear stress would be generated. Moreover, to allow rapid dewatering of the roadbed, the geotextile need to

preserve its permeability without losing its separating functions. Its filtration characteristics Must not be significally altered by mechanical loading.

Geotextile perform the filter mechanism for drainages in earth dams, in roads and highways, in reservoirs, behind retaining walls, deep drainage trenches and agriculture. 

3.2 GeogridsA Geogrids is geosynthetics material used to

reinforce soils and similar materials. Geogrids are commonly used to reinforce retaining walls, as well as sub bases or sub soils below roads or structures.

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Soils pull apart under tension. Compared to soil, georgics are strong in tension. This fact allows them to transfer forces to a larger area of soil than would otherwise be the case.

3.2.1 Types of GeogridsBiaxial Geogrids - roadsUniaxial Geogrids - wall/slope applicationsTriAx Geogrids - advanced systems solution for lower cost, increased reliability and longevity for paved and unpaved applications.

Fig.4.3 Geogrid FIG.4.4 a mechanically stabilized layer (MSL)

3.2.2 Applications of Geogrids in Roads & highwaysGeogrids are a proven solution for pavement reinforcement on road and highway

projects and greatly extend the lifespan of the pavement. Geogrids reduce pavement thickness by up to a third without impacting performance, which lowers installation and maintenance costs. The system can be deployed quickly, making it ideal for building temporary access roads over soft ground or for heavy vehicle loads.

3.3 GeonetA geonet is a geosynthetics material consisting of integrally connected parallel sets of

ribs overlying similar sets at various angles for in-plane drainage of liquids or gases. Geonets are often laminated with geotextile on one or both surfaces and are then referred to as drainage geocomposites. They are competitive with other drainage geocomposites having different core configurations.

3.3.1 Uses and Applications of geonetThey are frequently bonded with one or two layers of geofabric on each side (and are

therefore often referred to as drainage geocomposites) or can be used sandwiched between two geomembranes. The geofabrics/membranes stop the soil clogging the grid-like openings and reducing the drainage performance. Geonets can also be used as wall, slope or roof drainage systems, under structures such as embankments and roads to drain away groundwater and contribute to stability of the structure and resistance to frost.

3.4 Geocells Cellular Confinement Systems are popularly known as “Geocells”. Geocells are

strong, lightweight, three dimensional systems fabricated from ultrasonically‐welded High Density Polyethylene (HDPE) strips that are expandable on‐site to form a honeycomb‐like structure (Fig. 1).Geocells are filled with compact non‐cohesive soils which are confined within the cellular walls. The composite forms a rigid to semi‐rigid structure. The depth of the geocells as well as the size of each cellular unit can vary as per design requirements

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3.4.1 Application. Geocells in filled with sand / metal as subgrade improves the strength of the

pavement, reducing settlements, formation of reflective crack and pot‐holes. Besides, use of geocells not only reduces the thickness of the pavement section but also significantly reduces downtime due to maintenance.

3.5 GeocompositeSeveral moisture barrier configurations have been investigated and used in

geotechnical and geo-environmental projects. For example, an unsaturated drainage layer (UDL), such as sand, placed over a coarse-grained soil, such as gravel, is commonly used in landfill applications, whereas a geo-composite section, composed of a geotextile placed over a geonet, is commonly used in roadway applications.

3.6. Geomembrane

A geomembrane is very low permeability synthetic membrane liner or barrier used with any geotechnical engineering related material so as to control fluid (or gas) migration in a human-made project, structure, or system. Geomembranes are made from relatively thin continuous polymeric sheets, but they can also be made from the impregnation of geotextiles with asphalt, elastomer or polymer sprays, or as multilayered bitumen geocomposites. Continuous polymer sheet geomembranes are, by far, the most common.

3.6.1 Applications of geomembrane To control expansive soils To prevent infiltration of water in sensitive areas Beneath highways to prevent pollution from deicing salts Beneath and adjacent to highways to capture hazardous liquid spills Beneath asphalt overlays as a waterproofing layer

3.7 Geosynthetic Clay Liner

A Geosynthetic Clay Liner (GCL) is a woven fabric-like material, primarily used for the lining of landfills. It is a kind of geomembrane and geosynthetic, which incorporates a bentonite or other clay, which has a very low hydraulic conductivity. The resulting lower permeability slows the rate of seepage out of the landfill. Due to environmental laws, any seepage from landfills must be collected and properly disposed off, otherwise contamination of the surrounding ground water could cause major environmental and/or ecological problems. The lower the hydraulic conductivity the more effective the GCL will be at retaining seepage inside of the landfill. Bentonite composed predominantly (>70%) of Montmorillonite or other expansive clays, are preferred and most commonly used in GCLs. A general GCL construction would consist of two layers of geosynthetics stitched together enclosing a layer of processed sodium bentonite. Typically, woven and/or non-woven textile geosynthetics are used, however polyethylene or geomembrane layers or geogrid geotextiles materials have also been incorporated into the design or in place of a textile layer to increase strength.GCLs are produced by several large companies in North America, Europe, and Asia. The United States Environmental Protection Agency currently regulates landfill construction and design in the US through several legislations.

3.7.1 Applications of geosynthetic clay liner

The engineering function of a GCL is containment as a hydraulic barrier to water, leachate or other liquids and sometimes gases. As such, they are used as replacements for either compacted clay liners or geomembranes, or they are used in a composite manner to augment the more traditional liner materials. The ultimate in liner security is probably a three

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component composite geomembrane/geosynthetic clay liner/compacted clay liner which has seen use as a landfill liner on many occasions.

3.8 GeofoamExpanded polystyrene (EPS) is a very common product that is widely used for

packaging and in building construction. Manufacturing of EPS blocks begins with expandable polystyrene resin beads that are generally less than 3 mm in diameter and contain microscopic cells filled with a blowing agent. The usual blowing agents are pentanes or butanes and constitute about 5 percent of the bead weight. When exposed to steam under controlled pressure, the cell walls soften and the blowing agent expands. Individual resin beads enlarge by up to 40 times in volume to form pre-puffs. After a holding period to allow stabilization at at room temperature, the pre-puffs are poured to fill a recangular molding box. All six sides of the mold are fixed and more steam is injected through small perforations along the confining walls. The pre-puff in the molding box further expand and fuse to form a block. Geofoam blocks should be manufactured using modified beads that contain fire retardant additives. An EPS molder (manufacturer) can produce blocks of a standard size that is characteristic for the molding equipment at the plant. The range of block dimensions that can be manufactured in different plants are the following:.

3.8.1 Applications of Geofoams1 Road construction over poor soils2 Road widening3 Airport runway/taxiway

4.DISADVANTAGES OF GEOSYNTHETICS The exposed lifetime of geosynthetics, being polymeric, is less than unexposed as

when they are soil backfilled. Clogging of geotextiles, geonets, geopipe and/or geocomposites is a challenging

design for certain soil types or unusual situations. For example, loess soils, fine cohesionless silts, highly turbid liquids, and microorganism laden liquids (farm runoff) are troublesome and generally require specialized testing evaluations.

Handling, storage, and installation must be assured by careful quality control and quality assurance about which much has been written.

5. CONCLUSIONGeosynthetics have great potential to be used as cost-effective solutions for several

engineering problems. This paper presents recent advances in geosynthetic products, on the utilization of these materials in road construction.Therefore, the expectation is that innovations in products, types and properties will continue to take place, adding to the already vast range of applications of these materials.

REFERENCES1. Earth Reinforcement and Soil Structures, Colin J F P Jones2. en.wikipedia.org3. www.civil.utah.edu 4. Jorge G. Zornberg(2011) “ Advances in the Use of Geosynthetics in Pavement Design.” Geosynthetics India’115. Handbook of Geosynthetics(January 2002)

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