DEPARTMENT OF CIVIL ENGINEERING

COLLEGE OF ENGINEERING

TRIVANDRUM - 16

2010

COASTAL EROSION PREVENTION BY

GEOTEXTILE TUBE TECHNOLOGY

SEMINAR REPORT

Submitted in partial fulfilment of

the requirements for the award of M. Tech Degree in

2

Civil Engineering

(Geotechnical Engineering)

of the University of Kerala

Submitted by

DEEPA. K. A.

M2, Roll No. 091224

Guided by

Dr. P. VINOD

Assistant Professor


3


TRIVANDRUM – 16

2010



TRIVANDRUM - 16

UNIVERSITY OF KERALA

2010

BONAFIDE CERTIFICATE

4

This is to certify that this report titled “COASTAL EROSION PREVENTION BY GEOTEXTILE TUBE

TECHNOLOGY” is a bonafide record of the work done by DEEPA. K. A. (M2, Roll No.091224

Geotechnical Engineering) towards the partial fulfilment of the requirements for the award of M.

Tech. Degree in Civil Engineering (Geotechnical Engineering) of the University of Kerala during the

year 2010.

Guided by P.G. Professor

Dr. P. VINOD Dr. V. SYAM PRAKASH

Assistant Professor, P.G. Professor

Dept of Civil Engineering Dept of Civil Engineering

College of Engineering, College of Engineering,

Trivandrum. Trivandrum.

ACKNOWLEDGEMENT

I express my deep sense of gratitude to my guide Dr. P. Vinod, Assistant Professor,

Department of Civil Engineering, College of Engineering Trivandrum, for the valuable guidance,

constant encouragement and creative suggestions offered during the course of this seminar and

also in preparing this report.

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I express my sincere thanks to Prof. Sheela S, Head of the Department, Department of Civil

Engineering, College of Engineering Trivandrum, for her valuable support and advice.

I express my sincere thanks to Dr. V. Syam Prakash, P.G Professor, Prof. Mariamma Joseph,

Head of the Geotechnical Division, Dr. S. Sreekumar, Staff Advisor, Prof. Ajitha Bhaskar and Dr.

Girish M S, Seminar Co-ordinators Department of Civil Engineering, College of Engineering

Trivandrum for providing necessary facilities and their sincere co-operation.

My sincere thanks are extended to all the teachers of the department of Civil Engineering and

to all my friends for their help and support.

Above all I thank GOD, the almighty for his grace without which it would not have been

possible to complete this work in time.

DEEPA. K.A.

TABLE OF CONTENTS

TITLE PAGE NO.

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1. INTRODUCTION 1

1.1 DESIGN CONSIDERATIONS OF GEOTEXTILE TUBES 2

1.1.1 Properties of the filling material 2

1.1.2 Mechanical properties of geotextiles 2

1.1.3 Hydrodynamic stability 2

1.2 GEOTEXTILE TUBE SHAPE 3

1.3 HYDRAULIC STABILITY ANALYSIS OF GEOTEXTILE TUBES 4

2. INSTALLATION OF A GEOTEXTILE TUBE 6

2.1 Site Investigation 8

2.2 Site Preparation 8

2.3 Transporting the Slurry 9

2.4 Filling 10

2.5 Dewatering 11

3. CASE HISTORY 11

3.1 COASTAL EROSION PREVENTION MEASURES AT A BEACH

LOCATED AT THE EAST COAST OF KOREA 11

3.1.1 Site Description 11

3.1.2 2-D hydraulic stability analysis 13

3.1.3 Design and construction 15

3.1.4 Installation 15

3.1.5 Observation after construction 16

3.2 COASTAL EROSION PREVENTION MEASURES

AT A BEACH IN MEXICO 17

4. SUMMARY AND CONCLUSIONS 19

REFERENCES 20

ABSTRACT

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The use of geotextile in Civil Engineering applications is quite large and has

expanded very rapidly worldwide especially during the last decade. Supported by the

technological boom, geotextiles have invaded a large variety of domains and have won trust

and esteem around the world because of the advantages they guarantee in terms of easiness

and flexibility of use, rapidity of installation and long-term efficiency. Shore erosion is

currently causing millions of dollars worth of damage to shorelines and public properties

around the world. Without adequate protection, a very significant part of our coastline will

fall prey to the ravages of the sea. In recent years, because of the shortage of natural rock,

traditional forms of river and coastal structures have become very expensive to build and

maintain. Consequently, the materials used in hydraulic and coastal structures are changing

from the traditional rubble and concrete systems to cheaper materials and systems. One of

these alternatives employs geotextile tube technology in the construction of shore protection

structures, such as groins, jetties, detached breakwaters and so on. Recently, geotextile tube

technology has changed from being an alternative construction technique and, in fact, has

advanced to become the most effective solution of choice.

This report explains the design considerations, hydraulic stability analysis and also

the installation of geotextile tubes. The report also presents a few case histories where the

geotextile tube technology has been successfully implemented for shore line protection.

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1. INTRODUCTION

In recent years, traditional forms of river and coastal structures have become very

expensive to build and maintain because of shortage of natural rock. As a consequence, the

materials used in hydraulic and coastal structures are changing from traditional rubble and

concrete systems to cheaper materials and systems such as gabion, slags, geosynthetics and

so on. Moreover shorelines are being continually eroded by the wave action of the sea.

Geosynthetics are being increasingly used in civil and environmental applications. One of

these applications is the use of geotextile tube technology. Geotextile tubes, hydraulically or

mechanically filled with dredged materials, have been variously applied in hydraulic and

coastal engineering fields.

The geotextile tube technology is mainly used for flood and water control, but they

are also used to prevent beach erosion, and for shore protection and environmental

applications (Shin and Oh, 2007). The geotextile sheets are permeable, yet soil tight, so that

any excess water drains from the geotextile tube. This causes the tube height to decrease, so

that the tube may have to be pumped more than once in order to achieve the desired height

(Shin and Oh, 2007). There are inlets at the upper part of the tube where the pumping hose is

inserted. The number and interval of inlets are dependent upon the type of the soil being

used. Typical lengths and widths of geotextile tubes are 150-180 and 4-5m, respectively,

with the effective height of 1.5-2.0m (Shin and Oh, 2007). Some of the most attractive

advantages of geotextile tube technology are that it can be used for in-situ filling materials

by hydraulic pumping; it can also be implemented with lower costs and faster construction

than other technology. Because of the lower price and easier installation, geotextile tube

systems can be good alternatives for hydraulic and coastal structures. Dikes and levees are

among primary uses of geotextile tubes. Dikes up to 2.0m tall can be constructed to provide

flood protection. By stacking the tubes, an even greater height can be achieved. These tubes

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can also be attached to the top of a floodwall to provide greater flood control (Shin and Oh,

2007). Groins can be very effective when used for shoreline protection. Sand-filled

geotextile bags are a very reasonable alternative to other groin types. Sand-filled can also be

used for revetments or bulkhead protection (Shin and Oh, 2007). For geotextile tubes the

major design considerations are related to the integrity of the units during release and

impact, and the accuracy of placement and the stability under current and wave attack (Shin

and Oh, 2007).

1.1 DESIGN CONSIDERATIONS OF GEOTEXTILE TUBES

The following design aspects are of importance:

1.1.1 Properties of the filling material

The physical characteristics of the filling material are important factors of geotextile

tube design and construction. Types of soil and degree of saturation influence the final

geotextile tube shape. Field experience has demonstrated that it is possible to fill in the

geotextile tubes to 70% or 80% of the theoretical maximum circular diameter. The dredged

material filled in the geotextile can be any material capable of being transported

hydraulically. Naturally occurring beach or river sand is the perfect choice for structural fill.

1.1.2 Mechanical properties of geotextiles

The retention of fill and the structural integrity of a dredged material-filled tube are

provided by geotextile envelope. Functionally, geotextile selection is based on the

geotextile’s opening characteristics, which must match the fill particle size and permeability,

and must have sufficient strength to resist the filling pressures. A composite fabric shell is

sometimes used, since it incorporates both an inner non woven fabric for filtration and an

outer woven fabric for strength. Formulation of a geotextile tube, filled with pressurized

slurry or fluid, is based on the equilibrium of the encapsulating flexible shell.

1.1.3 Hydrodynamic stability

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Hydrodynamic stability is a very important factor for coastal and near shore

geotextile tube construction. In order to assess the stability of the filled geotextile tube

structure, current wave forces are to be estimated.

1.2 GEOTEXTILE TUBE SHAPE

To predict the tube shape filled with coarse-grained material is easier than that with

fine grained material, because of immediate settlement and effective free drainage of coarse

grained material. One of the methods to predict the tube shape variation with consolidation

process is the volume reduction method.

Volume reduction method

The volume reduction method (VRM) provides the tube height variation with the

desired density of slurry based on the volume-weight relationship. The governing

mechanism of this approximation is that the tube only change sits height during the

consolidation process. Also the approximation options of the computer program GeoCoPS

are two shape types (elliptical and rectangle); it was selected by the magnitude of height

drop, desired density, and final tube shape. To simplify the boundary condition and

influencing factor, the following assumptions are considered in these approaches:

The consolidating material has one-dimensional movement

The solidified slurry is fully saturated

The tensile strength of geotextile is ignored

The slurry density is uniformed

From the assumptions and using the basic volume weight relationships, the following

equation is obtained:

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= = = ……………………................. (1)

Where and are the decrease and the initial height of the tube, respectively, is the

specific gravity of the solid, is the initial void ratio, and and the initial and final

water contents of the fill material. The following equation can also be shown:

, ………………………….. (2)

Where and are the unit weights of slurry and consolidated soil, respectively.

By combining equations (1) and (2), the decrease in tube height can be estimated with

material inside densities.

1.3 HYDRAULIC STABILITY ANALYSIS OF GEOTEXTILE TUBES

The main problem in geotextile tube technology is lack of proper design criteria such

as hydraulic stability, structural functionality, and knowledge of their behavior during and

after construction. In the past, the design of these systems was mostly based on rather vague

experience than on valid calculational methods. More research, especially concerning large-

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scale tests and the evaluation of performance of projects already realized, is still needed.

The hydraulic stability analysis based on the 2-D limit equilibrium theory is briefly

described below.

2-D hydraulic stability analysis

Several causes are responsible for the structural failure of geotextile tube structures.

The hydraulic structural failure including sliding, overturning, bearing capacity failure, and

rotating and forcing associated with waves. In order to assess the stability of the filled

geotextile tube structure, current wave forces have to be estimated. The theoretical stability

analysis employed is 2-D hydraulic stability analysis, based on the linear wave theory and

geotechnical stability analysis method. The hydrodynamic pulsating load to a geotextile tube

is evaluated by Hiroi’s empirical equation and is given by:

= 1.5 …………………………………………………………………………... (3)

Where is the hydrodynamic pulsating load, the unit weight of water, and the

significant wave height. The gravity weight of a geotextile tube was calculated by

equivalent rectangular shape in the effective height. The factor of safety against sliding can

be expressed by:

= = …………………………………………………………… (4)

Where is the horizontal resistance, is the horizontal force, is the overburden

pressure and gravity weight of geotextile tube, is the hydrodynamic pulsating load,

the effective height, and the interface angle between the geotextile and the base sand. The

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factor of safety against overturning about the toe of an equivalent rectangularly shaped tube

can be expressed by:

= = ……………………………………………… (5)

Where is width of an equivalent rectangularly shaped tube. The overburden pressure and

gravity weight as transmitted to the base soil should be checked against the ultimate bearing

capacity of the base soil. The factor of safety against bearing capacity failure can be

determined by:

= = ; ……………(6)

Where is cohesion of the base soil, , the bearing capacity factors by the internal

friction angle of saturated base soil, the submerged unit weight of base soil, and the

eccentricity of the hydrodynamic pulsating load.

2. INSTALLATION OF A GEOTEXTILE TUBE

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A geotextile tube is a structure in the form of a tube made of a highly-resistant

geotextile woven envelope filled with materials. Sand is the best filling material, mostly

thanks to its incompressibility; but other types of pumpable inert materials can also be used.

The structure is built on site and filled through hydraulic pumping of local materials

inside the envelope. The structure is flexible, monolithic, continual, and very resistant to

water forces. The tube is made of a special geotextile produced to suit specific types of

applications. The geotextile has small pores capable of retaining the injected materials and

allowing, due to a great permeability, the flow out of water during the pumping phase

(Koffler et al. 2008). In addition, the geotextile, is highly strong, to resist the high tensions

occurring during the hydraulic filling and maintain its geometrical shape.

The tubes are custom-made and supplied in various sizes and lengths to suit design

and installation requirements, with a great variety of diameters and lengths according to

specific applications. The structure is normally dimensioned by the theoretical diameter, the

circumference and the length. The theoretical diameter of the tube normally ranges from

1.50 m to 5 m. Filling is carried out on site through a series of inlet ports placed on a regular

basis along the tube.

After filling, the structure does not reach the same height as the theoretical diameter;

but a maximum height of 60 to 70% of the diameter, depending on filling methods and

whether filling occurs below or above water surface. In special cases where a greater contact

area between the tube and the ground is needed, only partial filling is carried out. This

structure can also be equipped by a scour apron (Fig. 2.1). The scour apron protects the base

of the tube and reinforces its stability on ground. The scour apron may be placed under the

tube and on both sides or just on one side, depending on the type of structure and the

placement site (Koffler et al. 2008). It is placed before settling the tube structure then two

little anchor tubes are installed on both sides and filled hydraulically to serve as ballast at the

edge of the scour apron.

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Fig 2.1: Geotextile tube equipped by a scour apron (Koffler et al. 2008).

Different types of pumps are used to carry out the filling, ranging from

unsophisticated sinkable pumps to huge dredging pumps according to the needs. The type of

pumping system depends on the importance and complexity of the project and the specificity

of the site. The hydraulic pump is connected to local inlet ports placed along the tube.

A mixture of sand and water is pumped into the tube. The sand settles inside the

geotextile tube and the water “bleeds” from the pores of the geotextile and the filling

progresses. So, the inlet ports that are not used during the filling operation should be left

open to allow the evacuation of excess water. When the tube is filled to the required height,

the inlet ports are seamed (Koffler et al. 2008). Stresses in the encapsulating geosynthetics

due to slurry pumping pressure, makes the installation procedure a task that must be carried

out under extremely controlled conditions. The geotextile tubes after filling process

completed are shown in Fig 2.2 and 2.3.

Fig 2.2: Installation of geotextile tube (Koffler et al. 2008).

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Fig 2.3: Installation of a geotextile tube – filling completed (Koffler et al. 2008).

The installation procedure of geotextile tubes involve:

2.1 Site Investigation

Installation begins with a site investigation to determine factors that influence the

operations of an installation. First, the site must be evaluated to determine what equipment is

needed to complete the installation. The amount of pipe needed to transport the slurry from

the dredge to the geotextile tube must be determined. It is determined at this time if any

special equipment is needed in the operations. A site investigation determines the optimum

time of day to begin the site preparation in regards to tides, currents, and waterway traffic (it

will be less difficult at low tide with less traffic). Finally, all environmental concerns are

determined through the site investigation.

2.2 Site Preparation

Preparing the site for a geotextile tube installation begins with assembling the proper

equipment as predetermined by the site investigation. Some sites require leveling the area

(dry land) or digging a trench to aid the stability of the geotextile tube during filling. Site

preparation includes installing the scour apron (Fig 2.4). Once the apron and geotextile tubes

are in place and stabilized, filling can begin.

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Fig 2.4: Installation of a Scour Apron (Murphy, 1998).

2.3 Transporting the Slurry

There are two basic methods to transport the slurry to fill the geotextile tube. The

first method uses a small dredge just for filling the geotextile tube and the discharge pipeline

is connected directly to the geotextile tube. The second method is to use the normal dredge

and utilize a split pipe technique to fill the geotextile tube as seen from Fig 2.5. A ball valve

can be used to control the slurry pressure into the geotextile tube. If this method is used,

careful attention to the velocities must be considered to prevent the pipes from clogging.

Both methods have been used and have been successful. The determining factors for

selecting which method to use are economics and the size of the dredging project.

Fig 2.5: Split Pipe Method (Sprague, 1993).

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2.4 Filling

Once the method of dredging and transporting the slurry is determined and the site

has been prepared, then filling the geotextile tube can begin. The geotextile tube must be

restrained while filling because it will take some time for the solids to accumulate inside the

geotextile tube. Once there is enough buildup of solids accumulation, then the geotextile

tube will stabilize itself. However, even though one end of the geotextile tube is stable, it

still may be necessary to restrain the empty end because it may twist and roll. Depending on

the dredge, it may be necessary to hold the discharge pipe with a frame, backhoe, or crane

near the filling port for support. With a small dredge, the discharge line can usually be

directly connected to the fill port. A pressure gauge can be used to monitor the pressure

inside the geotextile tube as illustrated in Fig 2.6. Using GeoCoPS can aid in the filling

procedure by determining the pumping pressure needed to obtain a specific height of a

geotextile tube. It is important not to over pressurize the geotextile tube during filling for

obvious reasons. This is achieved by watching the pressure and leaving the fill holes open to

allow the water to escape more rapidly.

Fig 2.6: Pressure Gauge Connected to Inlet (Leshchinsky et al., 1996).

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The dredge material also affects the filling procedure. If the sediments are mostly

sand, pumping one time is usually the only chance the contractors will get (because a sand

slurry dewaters almost immediately), except to add sand to the fill holes to level off the

geotextile tube. With fine-grained sediments or a fluid mud, it may be necessary to pump a

few times to obtain a full geotextile tube. This is because the water takes longer to escape

from the sediments.

2.5 Dewatering

Dewatering depends on the fabric of the geotextile tube and the material being

pumped inside the geotextile tube. With sand slurry, dewatering is not a problem and takes a

relatively short period of time. However, if the sediments are fines (silt or clay), this process

may require a few days. There is no standard method for hydraulically filling geotextile tube

since this is a relatively new concept. Installation techniques may vary with each contractor,

thus experience of the contractor is a key to a successful installation.

3. CASE HISTORY

3.1 COASTAL EROSION PREVENTION MEASURES AT A BEACH LOCATED AT

THE EAST COAST OF KOREA

3.1.1 Site Description

Shore erosion was causing severe damage to shoreline scenic views and to public

property among the east coast of Korea. Shore erosion is caused by the energy of wave

attack, periodic tides, and currents which are produced by seasonal winds. The process of

shoreline east coast of Korea is most severe when the significant wave heights are varied

upto 4.0m range in winter season (Shin and Oh, 2006). The severe erosion process continues

even after early spring season during 4 months, as the shoreline have become stiffer and

high energy wave from current and storm can still attack them. In order to reduce the erosion

damage to beaches and shoreline, shore protection measures had to be applied every year.

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Effective methods of shore protection were designed to slow or stop the erosion process and

erosion control by dissipating wave energy and/or preventing shoreline attack. Therefore,

the decision-makers of many cities along the east coast of Korea have applied various types

of shore protection methods over the years. Considerable attention has been given to the use

of concrete segment type breakwaters to attenuate wave energy.

The officials considered another alternative solution to find more inexpensive and

environmental sustainable technology and geotextile tube technology was implemented in

Young-Jin beach on the east coast of Korea. The site plan of the Young-Jin beach is shown

in the Fig 3.1.

Fig 3.1 Site plan of Young-Jin beach (Shin and Oh, 2007).

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3.1.2 2-D hydraulic stability analysis

2-D hydraulic stability analysis results are shown in figures 3.2, 3.3and 3.4. The

geometry of the geotextile tube, the characteristics of the filling material, and the base soil

properties are the same as the field conditions at Young-Jin beach (Shin and Oh, 2007). The

variable parameters of the stability analysis are the filling ratio and the significant wave

height. They were varied from 85% to 95% and from 1.0 to 5.0m respectively. From the

results of 2-D stability analysis, the safety factor is decreased on increasing the filling ratio

and significant wave height. However the safety factors of sliding and overturning vary

exponentially. Also, the double lined tube is found to be more stable than single installed

tube.

Fig 3.2 SF of sliding (Shin and Oh, 2007).

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Fig 3.3 SF of overturning (Shin and Oh, 2007).

Fig 3.4 SF of bearing capacity failure (Shin and Oh, 2007).

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3.1.3 Design and construction

It was determined that two lines geotextile tube could be used at the Young-Jin

beach. For shoreline protection the geotextile tube was installed 1m below the water surface

and as deep as possible, firstly to avoid spoiling the scenery and secondly to reduce the

navigational risks. Geotextile tubes were designed two lines as detached breakwaters and

had to be installed in about 3.0m of water, 90-100m distant from the shoreline. A single

detached breakwater element implemented as a geotextile tube had a circumference 9.5m,

50m long and the effective height was 1.8m. It covered 240m of near shore along the

shoreline of Young-Jin beach (Shin and Oh, 2006).

The apron mat was installed as a fabric blanket to protect against scouring. The edge

of the fabric was folded back 0.5m and sewn forming a small tube that could be filled with

sand. These small tubes help anchor the scour blanket. A cutter section dredging ship was

used to fill the geotextile tubes and the large barge ship was used in the whole construction

process. Also special hardwares were required to connect the dredge discharge pipe to the

tube.

3.1.4 Installation

A total of eight geotextile tubes were installed at the Young-Jin cove. The shoreline

variation and water depth of the offshore area were also monitored (Shin and Oh, 2007).

Four of the two lines geotextile tubes were installed from south to north, spaced at 20.0m

intervals. The installation procedure involved:

Surveying the installation point

Installing the apron mat

Placing the geotextile tube

Connecting the injection nozzle and port of the tube

Dredging and filling the tube with soil

Checking the effective height

Completing the dredging and filling operation

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Before and during the hydraulic filling, the pumping pressure, speed and mixing

ratio of slurry were varied to determine the optimum value.

3.1.5 Observation after construction

Observations of the filling process show that settling and drainage occurred very fast.

The construction of one geotextile tube requires less than 1 hour and the desired final height

was achieved after only four dredging and filling steps. After 1 year in use, seaweed had

inhabited the surface of the submerged tube (Fig 3.5). Hence it can be concluded that the

polymer material used in their manufacture is unlikely to have an adverse effect on marine

life (Shin and Oh, 2007). Moreover, it can be environmentally sustainable to the adjacent

ecology. The test sites have been exposed to a number of severe storms common to the east

coast of Korea. This makes it difficult to evaluate the structures performance as a form of

innovative shore protection.

Over the short period of four observations, the variation of shoreline with the elapsed

time was extended into the sea during 3 months, because of the short term effectiveness of

wave absorption and decrement of sea bed soil migration. After 3 months however the

shoreline was re-eroded by tidal waves and geometrical reason. However the magnitude of

the re-erosion was relatively small compared to the extension of the shoreline. The water

depth in the near shore area decreased with elapsed time, and the sand gradually

accumulated around areas covered by the geotextile tube (Fig 3.6).

Fig 3.5 Tubes covered by seaweed (Shin and Oh, 2007).

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Fig 3.6 Sand accumulation by geotextile tube (Shin and Oh, 2007).

3.2 COASTAL EROSION PREVENTION MEASURES AT A BEACH IN MEXICO

A particularity of this beach system is that there are not many natural sediment

sources such as river discharges, so littoral balance may be easily broken by infrastructure

such as small harbors, piers and groins. The first attempts to control beach erosion were

individual actions undertaken to retain sediment for beach stabilization without considering

the consequences along the coast. By the end of 2002, the situation was critical, since many

beaches were almost fully eroded and risk of destruction due to extreme waves induced by

any hurricane with a path through the Gulf of Mexico was permanent.

The combination of wave climate, currents, tides and storm surges is the main cause

of beach erosion. Based on local experience in the past 20 years, any beach restoration

action has to be environmentally friendly and also it needs to consider possible negative

impact on adjacent beaches (Alvarez et al. 2007). Among the various alternatives for

submerged structures, geotextile tubes were chosen for their viability to cause wave

dissipation. The low costs for initial installation and maintenance, were also considered.

Geotextiles were installed upto a length of 4km in Yucatan. The geotextile tube cross-

section provided was as shown in Fig 3.7.

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Fig 3.7 Geotextile tube cross-section (Alvarez et al. 2007).

Fig 3.8 Geotextile tube inducing wave breaking for energy attenuation (Alvarez et al.

2007).

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Fig 3.9 Wave breaking process in (b) middle–high tide and (c) low-tide conditions

(Alvarez et al. 2007).

The geotextile tubes were installed along the shoreline and after 18 months of

monitoring they have been performing satisfactorily as parallel submerged breakwaters (Fig

3.8 and 3.9). The energy dissipation was generated by wave breaking due to the presence of

tubes. Efficiency of design depends highly on how precise is the evaluation of wave

transmission at the geotextile tubes. The tensile strength for geosynthetics is conditioned

mainly by slurry-pumping pressure. Most of the tubes were filled with pumping equipment

from island and offshore sediments banks, with no overstressed geotextiles detected.

4. SUMMARY AND CONCLUSIONS

Geotextiles are being used for a variety of Civil Engineering applications. One such

application being the use of geotextiles for coastal erosion prevention. Shore erosion is

currently causing millions of dollars worth of damage to our shorelines. Because of the

shortage of natural rock, the materials used in hydraulic and coastal structures are changing

from traditional rubble and concrete systems to cheaper materials and systems. One of the

methods for coastal erosion prevention is to employ geotextile tube technology in the

construction of shore protection structures. Recently, geotextile tube technology has

advanced to become the most effective solution of choice.

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The design considerations, hydraulic stability analysis and the installation of

geotextile tubes have been explained in this report. Further two case studies dealing with

coastal erosion prevention by geotextile tube technology have been discussed. The following

are the major conclusions reported:

1. Geotextile tubes performing as shore parallel low-crested structures have shown that

they are an effective and environmentally friendly alternative for shore stabilization.

2. 2-D hydraulic stability analysis conducted with reference to the field conditions at

Young-Jin beach indicated that:

The safety factor is decreased on increasing the filling ratio and significant wave

height.

The safety factor of bearing capacity varies linearly with filling ratio and significant

wave height. However, the safety factors of sliding and overturning vary

exponentially.

Also it was found that double-lined tube is more stable than single installed tube.

REFERENCES

1. Shin, E.C. and Oh, Y.I., (2006), “Using submerged geotextile tubes in the protection of

E. Korean shore”, Coastal engineering, Vol. 53, pp. 879-895.

2. Alvarez, I.E. and Rubio, R., Ricalde, H., (2007), “Beach restoration with geotextile tubes

as submerged breakwaters in Yucatan, Mexico”, Geotextiles and Geomembranes, Vol.

22, pp. 233-241.

3. Shin, E.C. and Oh, Y.I., (2007), “Coastal erosion prevention by geotextile tube

technology”, Geotextiles and Geomembranes, Vol. 25, pp. 264-277.

4. Koffler, A., Choura, M., Bendriss, A. and Zengerink, E., (2008), “Geosynthetics against

protection against erosion for river and coastal banks and marine and hydraulic

construction”, Journal of coastal conservation, Vol. 12, pp. 11-17.

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Coastal Erosion Prevention by Geotextile Tube Technology

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