Geotextiles

Table of contents

Chapter 1 Introduction

1.2 What Is Geotextile?

1.3 Detail

Chapter 2 Types of Geotextiles

2.2 Raw Material Of Geotextiles

2.3 The Basic Properties Of Geotextiles

Chapter 3 Functions Of Geotextiles.

3.2 Separation

3.3 Drainage

3.4 Filtration

3.5 Stabilization / Reinforcement

3.6 Erosion Control

3.7 Protection

3.8 California Bearing Ratio (CBR

Chapter 4 Manufacturing Techniques

4.2

Chapter 5 Identification Of Areas In Pakistan Where Geotextiles Can Be Used.

Chapter 6 SWOT Analyses Of The Situation In Pakistan.

Chapter 7 Installation Guidelines

Chapter-1

Introduction

Textile uses can not be only attached with apparel or upholstery, as with the advancement in technical textiles its uses are expanded. Geotextiles introduction have been taken 60 years back .According to the historical record, it is believed that the first applications of geotextiles were woven industrial fabrics used in 1950’s. One of the earliest documented cases was a waterfront structure built in Florida in 1958. Then, the first nonwoven geotextile was developed in 1968 by the Rhone Poulence company in France. It was comparatively thick needle-punched polyester, which was used in dam construction in France during 1970.

1.1 What is geotextile?

As we know, the prefix of geotextile, geo, means earth and the ‘textile’ means fabric. So we can say the type of fabric used in earth. According to the definition of ASTM 4439, the geotextile is defined as follows:

"A permeable geosynthetic comprised solely of textiles. Geotextiles 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."

Or simply,

“Permeable textile materials used in contact with soil, rock, earth or any other geotechnical related material that is an integral part of a civil engineering project, structure or system.”

The ASAE (Society for Engineering in Agricultural, Food, and Biological Systems) defines a geotextile as a

"Fabric or synthetic material placed between the soil and a pipe, gabion, or retaining wall: to enhance water movement and retard soil movement, and as a blanket to add reinforcement and separation."

A geotextile should consist of a stable network that retains its relative structure during handling, placement, and long-term service. Other terms that are used by the industry for similar materials and applications are geotextile cloth, agricultural fabric, and geosynthetic

Geotextiles are fabrics which are used in road, dam, river, drainage and ocean construction sites for preventing erosion on river banks and seashores, and around piers and bridges, in paving of roads and as filtration fabrics in dam construction and as silt retainers to prevent erosion at construction sites. Geotextiles prevent the movement of soil or sand when placed in contact with the ground. When used in paving roads, geotextiles help maintain structural integrity of the road surface.

1.3 Detail:

There are many different types of geotextile-type materials. Two geotextiles that have many potential applications in agriculture are woven and nonwoven geotextile fabrics. The type of geotextile fabric that was selected for this project, and therefore the focus of this publication, is nonwoven fabric (needle punched). The nonwoven fabric is made with 100 percent polypropylene fibers that are mechanically interlocked by needle punching and/or heat setting. This proprietary process creates very compact three dimensional fabrics that are highly permeable and extremely tough. Since geotextile fabric is a petrochemical-based polymer that is essentially chemically and biologically inert, it will resist decomposition by bacterial or fungal action. However, these fabrics are susceptible to deterioration from ultraviolet (UV) light.

Geotextile fabric is available in weights ranging from 3.5 to 18 ounces per square yard. The fabric comes in rolls much like carpet, and is stabilized for UV resistance. A typical roll of nonwoven fabric contains 500 square yards (range is 275 to 700 square yards), with dimensions typically 12.5 to 15 feet in width, and 120 to 450 feet in length. The roll comes covered with plastic to prevent UV deterioration and also to prevent the roll from becoming waterlogged before installation (it is much like a sponge). The shipping weight is in the range of 170 to 220 pounds, but geotextile fabric will weigh much more if allowed to take on moisture before installed. Therefore, the fabric should be stored in a dry location and out of direct sunlight until installation. A more complete description of the physical property requirements of nonwoven geotextiles is given in USDA Natural Resources Conservation Service (NRCS) Design Note 24, Guide for the Use of Geotextiles (see Bibliography).

Chapter 2

2.1 TYPES OF GEOTEXTILE

In general, the vast majority of geotextiles 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

2.2 RAW MATERIAL OF GEOTEXTILES

The four main polymer families most widely used as the raw material for geotextiles are:

Polyester
Polyamide
Polypropylene
Polyethylene

The oldest of these is polyethylene, which was discovered in 1931 in the research laboratories of the ICI. Another group of polymers with a long production history is the polyamide family, the first of which was discovered in 1935.The next oldest of the four main polymer families relevant to geotextile manufacture is polyester which was first announced in 1941.The most recent polymer family relevant to geotextiles to be developed was polypropylene, which was discovered in 1954. The comparative properties of these four polymers are shown in following Table.

	Polyester	Polyamide	Polypropylene	Polyethylene
Strength	H	M	L	L
Elastic modulus	H	M	L	L
Strain at failure	M	M	H	H
Creep	L	M	H	H
Unit weight	H	M	L	L
Cost	H	M	L	L
Resistance to:
U.V. light stabilized	H	M	H	H
Unstabilized	H	M	M	L
Alkalis	L	H	H	H
Fungus, vermin	M	M	M	H
Fuel	M	M	L	L
Detergents	H	H	H	H

H: High; M: Medium; L: Low

Table 1

2.3-THE BASIC PROPERTIES OF GEOTEXTILE

The properties of polymer material are affected by its average molecular weight and its statistical distribution. Increasing the average MW results in increasing:

tensile strength
elongation
impact strength
stress crack resistance
heat resistance

Narrowing the molecular weight distribution results in:

increased impact strength
decreased stress crack resistance
decreased processability

Increasing crystallinity results in:

increasing stiffness or hardness
increasing heat resistance
increasing tensile strength
increasing modulus
increasing chemical resistance
decreasing diffusive permeability
decreasing elongation or strain at failure
decreasing flexibility
decreasing impact strength
decreasing stress crack resistance

Chapter 3

THE BASIC FUNCTION OF GEOTEXTILE

. There are at least 80 specific applications area for geotextiles that have been developed; however, the fabric always performs at least one of five discrete functions. Their rise in growth during the past fifteen years has been nothing short of awesome. They are indeed textiles in the traditional sense, but consist of synthetic fibers rather than natural ones such as cotton, wool, or silk. Thus biodegradation is not a problem. These synthetic fibers are made into a flexible, porous fabric by standard weaving machinery or are matted together in a random, or nonwoven, manner. Some are also knit. The major point is that they are porous to water flow across their manufactured plane and also within their plane, but to a widely varying degree

Separation
Drainage
Filtration
Stabilization / Reinforcement
Erosion Control

6. Protection

3.2 Separation

Geotextiles function to prevent mutual mixing between 2 layers of soil having different particle sizes or different properties. Following table shows the required properties for separation:

Table 2 The required properties for separation

	Mechanical	Hydraulic	Long-term Performance
During installation	Impact resistance Elongation at break	Apparent opening size ( A.O.S.) Thickness	UV resistance
During construction	Puncture resistance Elongation at break	Apparent opening size ( A.O.S.) Thickness	Chemical stability UV resistance
After completion of construction	Puncture resistance Tear propagation resistance Elongation at break	Apparent opening size ( A.O.S.) Thickness	Chemical stability Resistance to decay

Table 2

3.3 Drainage :

The function of drainage is to gather water, which is not required functionally by the structure, such as rainwater or surplus water in the soil, and discharge it.

The required properties for drainage

	Mechanical	Hydraulic	Long-term Performance
Permanent drainage function	Influence of normal overburden pressure	Permeability Thickness Apparent opening size (A.O.S.)	Chemical properties of water and soil Chemical stability Decay resistance
Temporary drainage function	Influence of normal overburden pressure	Permeability Thickness Apparent opening size (A.O.S.)

Table 3

3.4 Filtration :

Filtration involves the establishment of a stable interface between the drain and the surrounding soil. In all soils water flow will induce the movement of fine particles. Initially a portion of this fraction will be halted at the filter interface; some will be halted within the filter itself while the rest will pass into the drain. The geotextile provides an ideal interface for the creation of a reverse filter in the soil adjacent to the geotextile. The complex needle-punched structure of the geotextile provides for the retention of fine particles without reducing the permeability requirement of the drain

The required properties for Filtration:

	Mechanical filter stability	Hydraulic filter stability		Long-term performance
Permanent filter function	A.O.S. Thickness		Geotextile permeability	Chemical properties of water and soil Chemical stability Decay resistance
Temporary filter function	A.O.S. Thickness		Geotextile permeability

Table 4

3.5 Reinforcement

Due to their high soil fabric friction coefficient and high tensile strength, heavy grades of geotextiles are used to reinforce earth structures allowing the use of local fill material

The required properties for reinforcement

	Mechanical	Hydraulic	Long-term performance
Base failure	Shear strength of bonding system	Hydraulic boundary conditions	Chemical and decay resistance
Top failure	Tensile strength of geotextile Geotextile/ soil friction	Hydraulic boundary conditions	Chemical and decay resistance
Slope failure	Tensile strength of geotextile Geotextile/ soil friction		Creep of the geotextile/ soil system Chemical and decay resistance

Table 5

3.6 Protection:

Erosion of earth embankments by wave action, currents and repeated drawdown is a constant problem requiring the use of non-erodable protection in the form of rock beaching or mattress structures. Beneath these is placed a layer of geotextile to prevent leaching of fine material. The geotextile is easily placed, even under water

The required properties for protection

	Mechanical	Long-term performance
Tunnel construction	Burst pressure resistance Puncture resistance Abrasion resistance	Chemically stable: pH=2-13 Decay resistance
Landfill and reservoir geomembrane construction	Puncture resistance Burst pressure resistance Friction coefficient	Chemically stable: pH=2-13 Decay resistance
Flat roof construction	Puncture resistance	Chemical compatibility

Table 6

3.7 Stabilization

In Ground Stabilization Fabrics

3.8 California Bearing Ratio (CBR)

The primary function that a Geotextile will serve in the design of roads depends on the soil strength on which the road is being constructed. A parameter to measure soil strength is California Bearing Ratio (CBR)

Geotextile Primary Function and Soil CBR

Soil Sub-Grade Description	CBR	Primary Function	Cost Justification
Soft	3	Reinforcement	Significantly less stone base utilization
Intermediate	3-8	Stabilization	Less stone base and Longer life time
Firm	8	Separation	Much longer lifetime

Table 7

CBR > 08

With the use of geotextiles, lifetime of roads increases by 10-15 times

Chapter-4

4.1 Manufacturing Techniques of Geotextiles:

I - NONWOVENS (NEEDLE PUNCHED)

II - Woven (weaving of tape polypropylene yarn)

III- knitted

5.2-NEEDLE PUNCHED NONWOVENS

1. INTRODUCTION

Worldwide, the needlepunching industry enjoys one of the greatest successes of any textile related process. The needlepunching industry around the world is a very exciting and diverse trade involving either natural or both natural and synthetic fibers.

2. PROCESS

The needlepunch process is illustrated in fig. 1. Needlepunched nonwovens are created by mechanically orienting and interlocking the fibers of a spunbonded or carded web. This mechanical interlocking is achieved with thousands of barbed felting needles repeatedly passing into and out of the web.

Fig. 1: Needle punching process

The major components of the needle loom and brief description of each are as follows:

2.1 THE NEEDLE LOOM (Fig-2 a & b)

The needle board : The needle board is the base unit into which the needles are inserted and held. The needle board then fits into the needle beam that holds the needle board into place.
The feed roll and exit roll. These are typically driven rolls and they facilitate the web motion as it passes through the needle loom.
The bed plate and stripper plate. The web passes through two plates, a bed plate on the bottom and a stripper plate on the top. Corresponding holes are located in each plate and it is through these holes the needles pass in and out. The bed plate is the surface the fabric passes over which the web passes through the loom. The needles carry bundles of fiber through the bed plate holes. The stripper plate does what the name implies, it strips the fibers from the needle so the material can advance through the needle loom.

Fig. 2a: Needle loom

Fig. 2b: Needle penetration

2.2 THE FELTING NEEDLE

The correct felting needle can make or break the needle punched product. The proper selection of gauge, barb, point type and blade shape (pinch blade, star blade, conical) can often give the needlepuncher the added edge needed in this competitive industry (fig. 3).

Fig. 2: Types of needles

The gauge of the needles is defined as the number of needles that can be fitted in a square inch area. Thus finer the needles, higher the gauge of the needles. Coarse fibers and crude products use the lower gauge needles, and fine fibers and delicate fibers use the higher gauge needles. For example, a sisal fiber product may use a 12 to 16 gauge needle and fine synthetics may use 25 to 40 gauge needle.

The major components of the basic felting needle are as follows:

The crank: The crank is the 90 degree bend on the top of the needle. It seats the needle when inserted into the needle board.
The shank: The shank is the thickest part of the needle. The shank is that part of the needle that fits directly in the needle board itself.
The intermediate blade: The intermediate blade is put on fine gauge needles to make them more flexible and somewhat easier to put inside the needle board. This is typically put on 32 gauge needles and finer.
The blade: The blade is the working part of the needle. The blade is what passes into the web and is where the all important barbs are placed.
The barbs: The barbs are the most important part of the needle. It is the barb that carries and interlocks the fibers The shape and sized of the barbs can dramatically affect the needled product
The point: The point is the very tip of the needle. It is important that the point is of correct proportion and design to ensure minimal needle breakage and maximize surface appearance.

As the needle loom beam moves up and down the blades of the needles penetrate the fiber batting. Barbs on the blade of the needle pick up fibers on the downward movement and carry these fibers the depth of the penetration. The draw roll pulls the batt through the needle loom as the needles reorient the fibers from a predominately horizontal to almost a vertical position. The more the needles penetrate the web the more dense and strong the web becomes generally See fig. 4 a & b. Beyond some point, fiber damage results from excessive penetration.

Fig. 4a: Needle Action - Schematic

Fig. 4b: Needle action

3. TYPES OF LOOMS

There are three basic types of needle looms in the needlepunching industry. They are:

The Felting Loom
The Structuring Loom
The Random Velour Loom

The felting looms are the type just described. These needle looms may have one to four needle boards and needles from the top, bottom or top and bottom. The primary function of this type of loom is to do interlocking of fibers resulting in a flat, one dimension fabric. The types of products made with this process and needle loom are diverse and multifaceted. They exist in variety of industrial products, geotextileds, automotives, interlinings, home furnishings, etc. [2].

Structuring looms use what are called fork needles. Instead of carrying fibers into bedplate hole, the fork needles carry fiber tufts into lamella bars that extend from the entry to the exit of the needle loom (fig. 1). These fork needles carry large tufts of fibers into parallel lamella bars. These bars carry the tuft of fiber from the entry to the exit side of the loom. Depending on the orientation of the fork needle, a rib or velour surface is introduced (fig. 5). The most popular products made with structuring looms include home and commercial carpets and floor mats, automotive rib and velour products, wall covering and marine products.

Fig. 5: Structured needling

Random velour looms are the newest type of needle looms, having only been available since the mid 1980's. The random velour looms are used to produce velour surfaces. Unlike the structuring looms, the velour products produced by this loom are completely isotropic. It is almost impossible to distinguish the cross direction from the machine direction.

Unique to this type of needle loom is the bristle-brush, bed-plate system. Special crown type needles or fork needles are used in this loom design. The needles push fibers into a moving brush bed plate. The fibers are carried in this brush from the entry to the exit of the loom with zero draft. This allows for the completely non-linear look, perfect for molded products. Random velour type products have been very popular in the European and Japanese automotive industry. While almost all U.S. automotive producers have the random velour machine, this type of product has yet to become popular in this country. The most popular products made with this type of needle loom are almost all centered around the automotive industry.

3.1 Machine variable:

The most important machine variable is the depth of penetration and puncture density. The fiber travel through the web depends on the depth of penetration of the needle. The maximum penetration is fixed by the needle of the machine and depends on the length of the three sided shank, the distance between the needle plates, the height of stroke, and the angle of penetration. The greater the depth of penetration, greater is the entanglement of fibers within the fabric because more barbs are employed.

The puncture density i.e. number of punches on the surface of the feed in the web is a complex factor and depends on

· the density of needles in the needle board (Nd)

· the rate of material feed

· the frequency of punching

· the effective width of the needle board (Nb_T)

· the number of runs

The puncture density per run Ed_pass = [n*F] / [V*W]

Where, n= number of needles within a needleboard

F = frequency of punching

V = rate of material feed

W = effective width of the needle board

The puncture density in the needled fabric Ed_NVdepends on the number of runs N_pass;Ed_NV= Ed_pass* N_pass

The thickness, basis weight, bulking density and air permeability - which provide information about compactness of fabric are influenced by a number of factors. If the basis weight of the web and puncture density and depth are increased, the web density increases and air permeability is reduced (when finer needles and longer, finer and more tightly crimped fibers are used). Web density does not increase when finer fibers are needled with coarser needles. There is neither an increase nor a decrease in air permeability if the puncture density is increased.

As far as the strength of a needled nonwoven web, the situation is similar to that for compactness, namely that finer needles, finer and longer fibers, greater web basis weight and greater puncture depth and density, result in increased strength of the needled web. However, once a certain critical puncture depth or density has been reached, the rise in strength may be reversed. If the depth of the barb is decreased or the distance between the barbs is increased, the dimensional stability is improved during needling, and the web density and maximum tensile strength in relation to basis weight can be raised.

Chapter 5

5 - Identifying areas in Pakistan

Identifying areas in Pakistan where geotextiles could be used in the construction of roads to improve the condition and the life of the road. Every year billions of rupees are utilized in just maintenance of National Highway. If once geotextiles used in sever areas then this maintenance budget can be reduced upto three times.

A geotextiles is placed between existing sub-soils and the aggregate base to provide long-term soil separation and stabilization to the base and to prevent the silt and other contaminating soil fines from seeping up into the aggregate. This confining action maintains the thickness and load-bearing capacity of the aggregate base, and also reduces localized stress by redistributing traffic loads over a wider sub-grade area. Fabric is widely used in our region due to prevailing soil and climatic conditions

· Roads in interior of major cities i-e Karachi, Lahore and Faisalabad having drainage problems

· Karakorum highway

· Naran kaghan road.

· Zhob D I khan Road N-50

Applying geotextiles on requires areas/roads of Pakistan nearly 70% NHA budget for roads repairing & maintenance can be reduce.

5.2 Implicated areas in pakistan:

Case ( I )

On Peshawar to Islamabad Motorway (M-3) at 7^th and 8^th Km.

Case ( II ):

Karakorum highway

Case ( III ):

5.3- Implicated Examples:

Palm Jumeirah Island, Dubai

Beijing Olympics Architecture
Levees in New Orleans, Hurricane Katrina

Chapter6

SWOT analyses of the situation in Pakistan.

Strengths

Indigenous production of raw materials.

Existing machinery and setups can be used for the production of technical textiles.

Weaknesses

Lack of human expertise.

Absence of legislative encouragement

Opportunities

High pace of infrastructure development

Export opportunities.

Capturing market before others (India Bangladesh) get in.

Threats

Emerging strong markets of China and India.

Resistance to change to innovative technologies

Chapter 7

INSTALLATION GUIDELINES

Geotextile Placement

Direct placement of the geotextile on the prepared site is usually preferable. Generally, it is advisable to leave vegetative cover such as grass and weeds in place to provide a support matting for construction activities. The geotextile should be rolled out flat and tight with no wrinkles or folds. The rolls should be oriented as shown on plans to insure the principal strength direction of the material is placed in the correct orientation. Adjacent rolls should be overlapped or seamed as a function of subgrade strength (CBR). Prior to fill placement, the geotextile should be held in place using suitable means such as pins, piles of soil, etc. so that it does not move around during fill placement.

Fill Placement

Fill should be placed directly over the geotextile in 20cm (8in) to 30cm (12in loose lifts. For very weak subgrades, 45cm (18in) lifts or thicker lifts may be required to stabilize the subgrade, as directed by the engineer.

Most rubber-tired vehicles can be driven at slow speeds, less than 16km/h (10mph) and in straight paths over the exposed geotextile without causing damage to the geotextile. Sudden braking and sharp turning should be avoided. Tracked construction equipment should not be operated directly upon the geotextile. A minimum fill soil thickness of 15cm (6in) is required prior to operation of tracked vehicles over the geotextile. Turning of tracked vehicles should be kept to a minimum to prevent tracks from displacing the fill and damaging the geotextile.

Cost consideration

Costs for geotextiles range from $0.50 to $10.00 per square yard, depending on the type chosen

Acknowledgements

Madam Hafsah Riaz (for guiding throughout project)
SKB (for providing access to civil engineering uses)
Fresinet Islamabad ( for providing samples)
PROOPEX. USA (for providing samples and manufacturing techniques)
……. (For providing raw material i-e 100% polyester)

References

1. Engineering uses of geotextiles (department of army and the airforce)

2. Horrocks, AR & Anand SC, Handbook of Technical Textiles, 2008, Woodhead,

3.DuPont Typar SF Geotextile, Technical Handbook,

4. Koerrner, George R, Geotextile Separation Study, Geotechnical Fabrics Report, Vol.

5. Yang, SH., Al-Qadi, IL., Cost-effectiveness of using Geotextiles in Flexible

6.Pavements, Geosynthetics International, 2007, Vol. 14, No. 1

7. Military Soils Engineering, Publication of Departments of the Army, Washington D.C,

8. Narejo, Dhani., Marienfeld, Mark., Hawkins, Bill and Lacina, Bruce., Long-Term

9. Performance Using Separation Geotextiles, Better Roads, Vol. 75, No. 1, pp 26-27

10. Hayat, Khizar., Geotechnical Zonation and their relation to the Geology of Pakistan,

11. The Nonwovens Handbook, INDA, Association of the Nonwoven Fabrics Industry, 1988

12. White, C. F.: Hydroentanglement Technology Applied to Wet Formed and Other Precursor Webs, TAPPI Nonwovens Conference, 1990, 177-187

13. Vaughn, E.: Spunlaced Fabrics, Canadian Textile Journal, October 1978, 31-36

14. Drelich, A.: A Simplified Classification of Nonwoven Fabrics, Sixth Annual Nonwovens Conference, University of Tennessee, Knoxville, 1988

15. Shivers, Joseph C., Popper, Peter, Saffer, Henry W.: The mechanical and Geometric Properties of Spunlace Fibrous Structures, INDA- TEC 1976, Symposium Papers

16. Vuillaume, Andre M.: A Global Approach to the Economics and End Product Quality of Spunlace Nonwovens, Tappi Journal, v.74, Aug '91, 149-152

17. Widen, Christian B.: Forming Fabrics for Spunlace Applications, Tappi Journal, v.74, May '91, 149-153

18. EDANA’s 1989 UK Nonwoven Symposium

19. "Spunlace technology today" 1989

20. " Spunlaced nonwovens overview" Nonwoven Industry, Feb. 1999

21. " The study on the mechanical properties of spunlaced nonwoven" 16^th polymer symposium Vol.9, PP 433-436, Jun.1993

22. Robert M. Koerner ‘Designing with Geosynthetics’, 1998

23. John N.W. M ‘ Geotextile ‘, 1987

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