1 Geosynthetics&Geosystems Pilarczyk Pres Final

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Developments in Design and Application of Geosynthetics and Geosystems

in Hydraulic and Coastal Engineering

Krystian W. PilarczykFormer: Rijkswaterstaat, Road and Hydraulic Engineering Institute,

Delft, the Netherlands

HYDROpil Consultancy, Zoetermeer, the Netherlands

[email protected]

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Developments in Design and Application of Geosynthetics and

Geosystems in Hydraulic and Coastal Engineering

General IntroductionPart I: Geosynthetics in RevetmentsPart II: Geosystems (geotextile systems)

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Why geosynthetics/geosystems?Critical review of geosystems in hydraulic/coastal

engineering

• Geosynthetics applications are associated mainly with ground engineering (soil mechanic engineers)

• Geosynthetics have already transformed geotechnical engineering to the point that it is no longer possible to do geotechnical engineering without geosynthetics (Giroud, 1987)

• Why not (or less) in hydraulic and coastal engineering ?!

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Why geosynthetics/geosystems? Why not in hydraulic and coastal engineering?

• The design of geosystems was in the past based more on rather vague experience than on generally valid (accepted) calculation methods.

• Contrary to research on traditional materials and systems there was little systematic research on the design, stability and performance of geosystems

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Why geosynthetics/geosystems?

• the modern design approach is characterized by making a choice from a number of suitable alternatives

• the shortage of natural resources• sometimes necessity (filters under

water)• (often) cheaper and/or easier execution• available in a wide range of properties

Design process

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Why geosynthetics/geosystems? Why not in hydraulic and coastal engineering?

• Past and recent research in the Netherlands, USA, Germany, Japan on a number of geosystems has provided results which can be of use in for preparation of design guidelines and design

• We should convince the design engineer that geotextile systems can be a good and usually cheaper alternative to the more traditional materials and systems

• Therefore: “Geosynthetics and Geosystems in Hydraulic and Coastal Engineering”

www.Balkema.nl; published in 2000

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Overview of geosynthetics/

geosystems

• Revetments• Fill-containing geosystems• Geocontainers• Geotextile forms for sand• Screens and curtains• Inflatable dams• In dams and dikes• Erosion control

(design methodology)

(geosynthetics: properties&specifications)

reality

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Why design methodology?

• integrated design: geotextiles and geosystems are only a part (or a component) of the total structure/project and they should be treated and integrated in the total perspective of a given project

• basic knowledge of total design (aspects and principles) and basic knowledge of geosynthetics properties/specifications

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Systems & Materialsexamples

First: solve the problem( functional design)

Then: systems & materials

(structural design)

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s / tan= L

H

gT

H2 = s 2

and

Breaker index

L=gT2/2π=1.56T2

Llocal =T (gh)^0.5

h= local depth in front of structure

Wave attack and Interactions with

structures

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Geosynthetics: types and properties

Terrafix non-woven composite

Wovens vs. Non-wovens

Specifications

Example of woven materials

Remarks on specifications: woven vs. non-woven

Wovens: high strength available, small elongation, bad performance at puncturing

Non-wovens:lower strength, high elongation, good performance at puncturing,

Good soil protection (if thick, i.e., needle-punched)

Elongation at break

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Bed and bank protection

/mattresses/

high pulling forces - high tensile strength needed (wovens)

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Composite products for special applicationsWoven for strength

Non-woven for filtering or surface protection(The type of interconnection is very important for performance)

Also non-woven composites

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Specifications and Certifications

• CEN (European Normalization)

• ASTM

(American Society for Testing and Materials)

Each manufacturer has to provide specifications according to international standards and certifications

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Part I

Geosynthetics in Revetments

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Alternative revetment systemsconventional ???

• Block mattresses

• Concrete geomattresses

• Sand mattresses

• Sand bags

• Wave load:– Cover layer stability– Geotechnical stability of subsoil

• Load by high flow currents

Geotextiles in revetment structuresHow to avoid failure ?

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q’ y

bq

b(q+ q)

y

D

cracked matress

b

filter

liftbreaking wave

WAVE ATTACKUplift of block

mat or mattresses

• Λ leakage length, characterises the structure

• At certain wave load:

– small leakage length => low uplift pressure

– (high k’ gives pressure relief)

– large leakage length =>high uplift pressure

or blocks

D

MATTRES

PERM :

FILTER

k

k‘

b

'/

Dk

bkD

0.67-op

0.33scr

k

k

b

D f =

DH

bkD

k '

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Prototype or large-scale verification

uplift

internal erosion

Evidence of failure

Stability criteria revetments: wave attackFor first estimation/conceptual design)

bop

s

cr

cosF =

DH

L / H

tan =

opsop

Breaker indexF=2.25 riprap

F= 3-3.5 basalt

F=4-6 blocks

b = 0.5 for rip rapb = ½ to 2/3 for blocksBlock revetments

op

0.67

scr Df =

DH 0.67-

op

0.33scr

k

k

b

D f =

DH

Usually in diagram form:

3/2op

s

cr

F =

DH

with maximum 8.0 = DHs

cr

www.tawinfo.nl

Example of stability diagram

More examples can be found in:

Dikes and Revetments, 1998, ed.K.W. Pilarczyk

http://books.google.nl/books?ct=title&q=Coastal+Protection+,+Pilarczyk&lr=&sa=N&start=40

Example of composition and construction (Basalton)

Geotextile filter

Cushion layer

Clay or sand

Basalton

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Block mats

Cabled system

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Cabled mat

Blocks connected to geotextile by pins

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bkD

k '

Importance of proper composition/ leakage length

'/

Dk

bkD

example

or

L / H

tan =

opsop

0.67-op

0.33scr

k

k

b

D f =

DH

Combined resistance/permeability

influence of geotextile

Geosynthetic is only one of the components involved

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slip circle

Compressible pore water + Pressure fluctuations

Reduced grain contact in sand

Local sliding

Local geotechnical (in-)stability

slip circle

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Design diagram of geotechnical stability• Load: Waves (& gravity

component along slope)

• Strength: Weight (cover layer + filter layer)

1 : 2

0.2 0.4 0.6 0.8D+b (m)

1 : 3

1.0

H(m)

s

0.5

1.5

slope1 : 5

D

MATTRES

PERM :

FILTER

k

k‘

b

Geotextiles; comparison with granular filters

Possible effectiveness of geotextile in filter: sieve curves and situation

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Filter concepts

Hydraulic gradients due to waves

NL: geometrically sandtight: O90 < D90

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Design

diagram

for

geotextile

filters

Delft Hydraulics

calculation programs

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Geotextile on clay

Following geometrically closed rules provides very closed geotextile susceptible to clogging. Clay (due to cohesion) has 3 times or more resistance to erosive forces. Proposed: calculate the opening of geotextile (al least) just as for sand. No official rules on that point are known (except NL).

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Geomats and GeomattressesPROFIX-sand-sausages mat

Concrete-filled geomattresses

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Sand mat (a measure for unstable soils)

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Erosion Control

Geoweb

3dim Composite mat

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foto van betonmatras

Stability of Concrete mattresses under wave attack

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before and after the storm

Lack of design criteria

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local settlementof subsoil

filterpoint:relief upliftpressure

geotextile

upliftpressure

waveimpact

sa n d o r fi l t e r

Damage hazards

Theory of block revetments can be applied to concrete geomattresses

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Combined permeability of a system

bkD

k '

Influence of leakage length

0.67-op

0.33scr

k

k

b

D f =

DH

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Stability of Synthetic Gabions in WavesTUDelft: Master of Science Thesis on the Application of Synthetic Grids in Mattress

Gabion Constructions and the Stability in Waves,June 2008

Mattress construction

Pilarczyk’s stability relation improved

friction

long

shortshort

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Puncturing

Falling stones

References online

http://books.google.nl/books?ct=title&q=Coastal+Protection+,+Pilarczyk&lr=&sa=N&start=0

http://www.library.tudelft.nl/ws/search/publications/theses/index.htm?to=2008&de=Hydraulic+Engineering&n=10&fr=2008&s=1&p=2

http://www.kennisbank-waterbouw.nl/

www.tawinfo.nl (select English, downloads)

http://www.wldelft.nl/rnd/publ/search.html(insert for Author: Breteler, Gent, or other name)

http://www.vandermeerconsulting.nl/

http://www.delftcluster.nl/

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Conclusion• Design methods are derived on basis of theory,

giving reasonable results, for various alternative revetments (including geotextiles):– Block mattresses (and interlocking blocks)– Concrete mattresses– Sand mattresses– Geosystems (sand bags, sand containers etc)– Gabions (and Reno-mattresses)

Covering Wave load and Flow load

• Necessary future research:– experimental verification (new products)– refining of theory

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Discussion

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Part II

Geosystems Geotextile Systems

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Innovation

in

Geosystems

Project approach and Design process

wide view

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floaters

Geosystems in coastal engineering:

Principe of inclined curtain as a coastal protection measure

anchores

Double row of curtains

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Kliffende HouseSylt Island

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Geobags

Repair

Application Geobags

Usually as temporary structures/measures

Filled with sand or concrete

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Geobags; execution aspects

B-B

Description: Date: Feb 2003

Scale: n.t.s.

2.5m Soft Rock Dimensions

Full Container

Section A-A Section B-B

2.5m Soft Rock Sea Wall Proposal

This document is not to be considered a full design and is provided without obligation. Complete engineering design must be performed by a suitably qualified engineer

3

650

2 4001 800

650

2 400

1 800

A A

B

B

3

B-B

B-B

B-B

B-B

B-B

B-B

B-B

B-B

B-B

5223R (2.5m )Soft Rock Containers

terrafix 600R 0.0 AHD

-1.0 AHD

Toe Detail

terrafix 600R

5223R (2.5m )Soft Rock Containers

Encapsulated self healing toe

Wall X-Section

Toe Detail

2152R (0.75m )Soft Rock Containers

3

3

3

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Construction of groin or breakwater with geobags

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Application of large geobags for underwater dam at Sylt

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Filling procedure

of Mexican system

Mexican (large) geobags filled with lean concrete

Large bags

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Geotubesimprovement of design

techniques and execution

stability

innovation

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Geotubes

• popular structure for shore protection

• shape and strength acc. to Leshchinsky method

• main problems: - durability (if exposed) - execution /positioning - stacking geotubes - filling with silty materials (consolidation) - seam strength

•

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Application Geotubes

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Design aspects of geotubes

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Design Geotubes Calculation shape and strength

Similar results using Leshchynski’s GeoCops

Palmerton method

Remarks on specifications: woven vs. non-woven

Seams and safety factors:

Seams 50 to 70% of strength

Safety factor ~2

Execution damage ~1.3

Chemical degradation ~ 1.5

Creep ~ 1.5

Usually total safety factor in calculation of required strength:

FS ~ 4 to 5

Elongation at break

For geotubes, if exposed, high strength needed

50 to 80

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Similar results using Leshchynski’s GeoCops

Calculation shape and strength

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Distribution of pressure along geotube perimeter

a) Circumferential tension distribution around a filled geotextile tube

b) Approximation of circumferential tension distribution in terms of [ ]Tmax c

10%-15%[ ]Tmax c100%[ ]Tmax c

50%-70%[ ]Tmax c

Circumferential tension distributionaround filled geotextile tube

Location of maximum circumferential tension

Filled geotextile tube

[ ]Tmax c

Filled geotextile tube

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Influence of fill-grade

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Influence of submergence

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Example of project:

AmWaj Island, Bahrein

at low water

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Functional design: wave transmission

Delft Hydraulics, 2000

Geotubes core+riprap

90Thailand

Execution

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Example of localized humps

Proper anchoring and pumping technique

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Typical section of geotextile tube applicationSurface protection: additional sheet ??? (usually does not work properly)

Durability (still a problem)

Usually, surface protection needed

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Holes repaired with HDPE covers

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Geocontainers - a new invention

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Geocontainers; filling procedure

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Application Geocontainers

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Terrafix Soft Rock (geocontainers)

Test geocontainer

non-woven

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Installation and dumping geocontainer

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Submerged reef, Gold Coast

a view

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Dumping loss material and Geocontainer

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Dumping trajectory of geocontainer

0.03

0.16

0.28

0.28

0.36

0.44

0.16

0.52

0.36

0.60

0.44

0.68

0.52

0.76

0.84

1.08

1.08

0.68 0.76

0.84

1.40

1.24 1.241.40

0.920.92

t = 2.12 s

0 10 20 30 40 50 x(cm)

splitbarge

leg ofsplitbarge

numbers = time(s)

Accuracy of placement still a problem (especially for depth larger than 10m)

high accuracy needed

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Large-scale geocontainer tests Delta Flume

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Large-scale tests Geotubes Delta Flume

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Stability geotubes&geocontainers - first approximation

.)(max0.25.1 D

Hs

cr

to

1 D

H5.0 s

cr

For geotubes parallel to wave attack

For geotubes perpendicular to wave attack;

For L/D > 4

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On crest

On slope

Stability large geobags on slopes (Oumeraci, 2002)

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Geocontainers Juan Recio 2007

PhD-study

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Juan Recio Formulae & comparisonUse thickness D= lc/4 ; min.D = lc/5

Current attack

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Numerical simulations by Recio

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Geocontainers: conclusions

• growing number of projects• design and execution (usually) based

on past experience• (still) limited documented experience• new design criteria are in

development• need for verification• need for well-documented experience

(a.o. accuracy of placing, performance)

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A.A. Balkema, Rotterdam

Remaining questions and closing remarks:

- durability

- execution

- damage

- quality control

www.balkema.nl

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Durability/long-term performance ??? to be or not to be

50 years

100 years

200 years

We have to answer that !

international cooperation/joined forces ( IGS !)

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Remember

In general it can be said that geosystems as well as all engineering systems and materials have (some) advantages and disadvantages which should be recognized before a choice is made. There is not one ideal system or material. Each material and system has a certain application at certain loading conditions and specific functional requirements for the specific problem and/or structural solution.

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Remember• When applying geosystems the major design

considerations/problems are related to the integrity of the units during release and impact (impact resistance, seam strength, burst, abrasion, durability etc.), the accuracy of placement on the bottom (especially at large depths), and the stability.

• When applying this technology the manufacturer's specifications should be followed. The installation needs an experienced contractor or an experienced supervision.

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Rememberalternatives

integrated approach

• Geosynthetic is only one of the components involved , and

• Geosystem is only a part of the total structure

• Design criteria needed, but

• Experience and engineering judgement play an important role in design and construction

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Monitoring of projects

Systematic (international) monitoring of realized projects (including failure cases) and evaluation

of the prototype data may provide useful information for verification purposes and further

improvement of prediction methods.

It is also the role of the national and international organizations to identify this lack of information and to launch a multiclient studies for extended

monitoring and testing programmes.

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Closing remarks• A number of concepts still need further

elaboration to achieve the level of design quality comparable with more conventional solutions and systems.

• A number of uncertainties can be solved in the scope of graduation works and doctoral dissertations. However, for a number of systems more practical experience is also still needed under various hydraulic conditions.

• The realization of this need is only possible if manufacturers, clients and researchers cooperate closely.

critical review of geosystems in hydraulic and coastal engineering

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Thank you

Geosynthetics are benefit for our Society

References online

http://books.google.nl/books?ct=title&q=Coastal+Protection+,+Pilarczyk

http://www.library.tudelft.nl/ws/search/publications/theses/index.htm?to=2008&de=Hydraulic+Engineering&n=10&fr=2008&s=1&p=2

http://www.kennisbank-waterbouw.nl/

www.tawinfo.nl (select English, downloads)

http://www.wldelft.nl/rnd/publ/search.html(insert for Author: Breteler, Gent, or other name)

http://www.vandermeerconsulting.nl/

http://www.delftcluster.nl/

www.balkema.nl (author: Pilarczyk)

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The end

And

Discussion

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Discussion

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Remarks on non-woven geotubes

We can calculate stresses for slurry in a non-woven geotextile; it should not make much a difference.  If the geotextile will deform significantly, we can do the calculations in parts.  Apply a little pressure, calculate the stress, use the geotextile modulus to find the elongation, add the elongation to the previous circumference L, use the modified L and run now for an increase pressure.  Repeat the process until reaching the desired pressure (or height of force T). 

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However, deformations are not part of the calculations.  If you wish to include its effects, you can do the following:

1. Use a certain specified height (or specified strength or specified pressure).  Any specified value should be smaller than the final value.

2. Run the program and get the reinforcement force.  Calculate by hand the change in circumference for geotextile (dL=T/k where k is the

stiffness of the geotextile). The new L is Ln=Lo+dL.3. Input Ln as the circumference, increase the pressure (or strength of

height) by another increment, and repeat the process. 4. When you get to the final increment of strength (or height of pressure) you have the final length of the circumference and final geometry.  The final length Lf minus the initial value Lo (un-deformed value) tells the

amount of deformation that is likely to occur under certain working conditions for any deformable membrane.  From experience, the amount of deformation (even is 5%) will have little effects on the final shape or

stress.  You can verify it by doing the process incrementally.

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