pipe stability

7/25/2019 Pipe Stability

1/60

STABILITY OF SUBMARINE

PIPELINES AGAINST

ENVIRONMENTAL LOADS

Dr.S.NEELAMANI

DEPARTMENT OF OCEAN ENGINEERING

IIT MADRAS


2/60

WHAT IS STABILIZATION OF SUBMARINE

PIPE LINES? WHY SUBMARINE PIPELINES

NEEDS TO BE STABILIZED?

1. TO PROTECT THE PIPES FROM WAVES AND

CURRENT LOADS, WHICH CAUSES

FLOATATION

SCOUR

SPANNING

RESONANCE VIBRATION

FATIGUE FAILURE

2. TO PREVENT FORCES DUE TO SOIL SLIDING

3. TO PREVENT DAMAGE DUE TO ANCHORS


3/60

WHAT IS THAT ONE SHOULD DO BEFORE

SELECTING SUITABLE STABILIZATION TECHNIC?

1. ENVIRONMENTAL CONDITIONS

WAVES AND CURRENTS

MUD SLIDES

TURBIDITY CURRENTS

LIQUEFACTION EFFECTS

EARTH QUAE EFFECTS

COMBINATION OF THESE FACTORS

2. IS BURIAL OF THE PIPELINE OR ITS E!POSURE IS

WARRANTED FOR THE OPERATION AND

MAINTENANCE?


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3. WHERE IS THE LOCATION OF THE PIPELINE? "

SURF ZONE OR AWAY?

#. IS THE PIPE LINE FOR TRANSPORTING

HAZARDOUS OR NON HAZARDOUS CARGO?


5/60

CLASSIFICATION

1. REFERENCE TO SEA BED

A. BURIED PIPELINESB. E!POSED PIPELINES

2. SEVERITY OF WAVE ACTION

A. PIPE LINES IN THE SURF ZONE

B. PIPELINES IN THE OFFSHORE ZONE


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3. TYPE OF CARGO TO BE TRANSPORTED

A. PIPELINES FOR HAZARDOUS CARGO

$E!% LPG, LNG, SULFURIC AND NITRIC ACIDS,

&METHANE, ETHYLENE, AMMONIA ETC.'

B. PIPELINES FOR NON HAZARDOUS CARGO

$E!% EDIBLE OIL, FRESH WATER, SEA WATER,

ETC.'


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MA(OR FORCES AFFECTING SUBMARINE PIPELINE

S.NO FORCE INTERACTION SYMBO

1 BUOYANCY FORCE WATER"PIPELINE FB2 ULTIMATE BEARING CAPACITYSOIL"PIPELINE FC3 DRAG FORCE WATER"PIPELINE F

D

# INERTIAL FORCE WATER"PIPELINE FI) LIFT FORCE WATER"PIPELINE FL* PULLOUT RESISTANCE SOIL"PIPELINE FO+ PASSIVE SOIL RESISTANCE SOIL"PIPELINE FP

SLIDING RESISTANCE SOIL"PIPELINE FS- ARTIFICIAL WEIGHT SOIL"PIPELINE FW1 IMPACT FORCE FOREIGN

OB(ECT "PIPELINE F!


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//

FD FI

FIFD

FL

FB

FC

FWFO

FP

FC

0 0

FC

FW FS

FL

FB

ELEVATED PIPE LINE


9/60

FL

FB

FL

FB

FL

FB

FC

FC

FWFW

FW

FDF

I

FD FI FDFI

FSB

B

FP

FSFP

FS0 0

0

SURFACE r PARTIALLY BURIED PIPELINE


10/60

FB

FB

FC

FC

N

N

FW

FW

0 0

BURIED PIPELINE


11/60

ENVIRONMENTAL FORCES

A. VERTICAL FORCES

B. HORIZONTAL FORCES

VERTICAL FORCES

1. BUOYANCY FORCE $FB'

2. HYDRODYNAMIC LIFT FORCE $FL'.

3. PIPELINE OR ARTIFICIAL WEIGHT $FW'#. SOIL BEARING CAPACITY $FC'

). PULLOUT FORCES $FO'.


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HORIZONTAL FORCES

1. DRAG FORCE $FD'

2. INERTIAL FORCE $FI'

3. SLIDING RESISTANCE $FS'

#. LATERAL SOIL RESISTANCE $FP'

). IMPACT FORCE $F!' $SOMETIMES VERTICAL

ALSO'


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BUOYANCY FORCES

POSSIBILITY FOR VE BUOYANCY FORCE $UPWARD'

1. FLUID DENSITY TO BE TRANSPORTED IS LESS

THAN THE SURROUNDING SEAWATER.

$E! % SANITARY WASTE WATER WITH SG OF.-- TO NATURAL GAS WITH A SG OF .+'.

2. DISCHARGE OF AIR OR OTHER GAS INTO A

PIPELINE CARRYING A LIQUID.

$E! % AIR ENTRAINMENT INTO A SEWAGE

EFFLUENT RESULTING FROM TURBULENT

MI!ING IN A CHLORINE CONTACT CHAMBER'


14/60

3.CERTAIN CONSTRUCTION METHODS CALL FOR THE

PRESSURIZATION OF THE PIPELINES WITH AIR AND

THEN THE CONTROLLED RELEASE OF AIR TO AID IN

LAYING THE PIPE ON THE BOTTOM.

$E! % THE BOTTOM PULL AND STRING FLOAT METHOD'

#.MATERIAL DENSITIES LESS THAN THE SURROUNDING

SEAWATER.

$E! % HIGH DENSITY POLYETHYLENE PIPE WITH ASPECIFIC GRAVITY OF .-))'.


15/60

LIFT FORCE

1. HORIZONTAL CURRENTS2. WAVE"INDUCED WATER PARTICLE MOTIONS

MAGNITUDE OF LIFT FORCE

1. OUTER DIAMETER OF THE PIPE, DO2. FLUID VELOCITY, U

3. RELATIVE CLEARANCE OF THE PIPE FROM

THE OCEAN BOTTOM.

$MA!IMUM FORCE CONDITIONS ARE

GENERATED WHEN THERE IS NO GAP

BETWEEN THE PIPE AND BOTTOM.'


16/60

THE LIFT FORCE, FL4 .) CLDOU2

WHERE

CL % LIFT COEFFICIENT

% MASS DENSITY OF THE SEAWATER

SELECTION OF PROPER LIFT COEFFICIENT IS VERY

IMPORTANT.

STEADY FLOW CONDITION

CL % 1., PIPE RESTING ON THE SEAFLOOR

.#, PIPE ONE"HALF DIAMETER ABOVE

THE BOUNDARY.


17/60

ARTIFICIAL WEIGHT

IF THE BUOYANCY AND LIFT FORCES ARE

GREATER THAN THE WEIGHT OF THE PIPE,ARTIFICIAL WEIGHT WILL BE REQUIRED.

WEIGHT OF THE CONCRETE COATING

FW4 .2)

C$ DC2

" DO2

'WHERE

C % THE SUBMERGED UNIT WEIGHT OF

COATING MATERIAL

DC

% OUTSIDE DIAMETER OF THE PIPE WITH

COATING

THE CRITERIA FOR WEIGHT OF THE CONCRETE

COATING%

FW 5 FB FL.


18/60

SPECIAL COLLARS

CAN BE FITTED TO THE PIPELINE AT REGULAR INTERVALS TO

OFFSET THE UPWARD FORCES

FW4 CBCHCLC6 LP

WHERE

BC % WIDTH OF THE WEIGHTED COLLAR

HC % E!POSED HEIGHT OF WEIGHTED

COLLAR

LC % LENGTH OF WEIGHTED COLLAR

LP % LENGTH OF THE PIPELINE

FOR VERTICAL STABILITY, THE E!CESS WEIGHT OF THE

PIPELINE $FW " FB " FL5 ' MUST NOT E!CEED THE ULTIMATE

BEARING CAPACITY OF THE SUBMARINE SOIL.


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ULTIMATE BEARING CAPACITY, FC

S % SUBMERGED UNIT WEIGHT OF SOIL

Z % EFFECTIVE BURIAL DEPTH OF PIPELINE

B % PRO(ECTED WIDTH OF THE PIPE IN

THE HORIZONTAL PLANE

$DIAMETER OF THE PIPE IF IT IS CIRCULAR'C % COHESIVE SHEAR STRENGTH

FC 4 $NQ SZ .) NSB' B FOR COHESIONLESS SOIL

4 $NC C SZ' B FOR COHESIVE SOIL

NC , NQ 7 N % BEARING CAPACITY FACTORS


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PULLOUT RESISTANCE

IF, FV 4 FW " FB " FL 8 , THIS UPWARD FORCE CAN BE

COUNTER BALANCED BY THE PULLOUT RESISTANCE

THROUGH PILES OR ANCHORS.

PULLOUT RESISTANCE OF PILES

FO 4 $.) PPZP2S TAN ' 6 LP$COHESIONLESS'

4 $C PPZP 6 ST' 6 LP$COHESIVE SOIL'

WHERE

% THE COEFFICIENT OF LATERAL EARTH

PRESSURE


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ST % THE SENSITIVITY OF THE COHESIVE SOIL

ZP % THE EMBEDMENT LENGTH OF PILE

PP % THE PERIMETER LENGTH OF PIPE

LP % THE LENGTH OF PIPE

% THE INTERFACE FRICTION ANGLE

PULLOUT RESISTANCE OF ANCHORS

FO4 WA SZ AA

WHERE

WA % THE SUBMERGED WEIGHT OF THE

ANCHOR.

AA % THE HORIZONTAL SURFACE AREA OF A

SOIL ANCHOR.


22/60

DRAG FORCE

FD4 .) CD

DOU2

CD % DRAG COEFFICIENT.

DESIGN VALUE OF CD

4 1. FOR STEADY FLOW CASE

INERTIA FORCE

FI4 .2) CIDO2DU6DT

DU6DT % THE HORIZONTAL ACCELERATION


23/60

CI % THE INERTIA COEFFICIENT.

$FUNCTION OF RELATIVE CLEARANCE OF THE PIPEFROM THE SEA FLOOR.'

4 3.3 FOR THE PIPE AGAINST THE SEA FLOOR

4 2. FOR THE PIPE GREATER THAN ONE"HALF

PIPE DIA ABOVE THE SEA BED BOUNDARY.

THE DRAG AND INERTIA FORCES

1. PERIODICALLY VARYING FORCES

2. NOT IN PHASE WITH EACH OTHER.


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SLIDING RESISTANCE

INTERFACIAL FRICTION BETWEEN THE SOIL AND PARTIALLY BURIED

PIPELINE

FS 4 FVTAN .) SZ2

TAN2$#)

62' FOR COHESIONLESS SOI

4 C B $.)SZ

2C' Z FOR COHESIVE SOIL OR MORE SIMPLY BY

FS4 FFV

.* 8 F 8 1.2 FOR COHESIONLESS SOIL

.1 8 F 8 .# FOR COHESIVE SOIL.

IF SUFFICIENT SLIDING RESISTANCE DOES NOT E!ISTS $FS8 FD FI',

THEN OTHER METHODS MUST BE INCORPORATED FOR LATERAL

STABILITY.


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PASSIVE SOIL RESISTANCE

FOR A PARTIALLY OR COMPLETELY BURIED

PIPELINE, HORIZONTAL FORCES ON THE PIPELINEARE RESISTED BY THE LATERAL PASSIVE FORCE OF

THE SOIL. THIS IS ESSENTIALLY THE MASS OF THE

SOIL RESISTING LATERAL DEFORMATION.

FP 4 NQSZ DO FOR COHESIONLESS SOIL

4 NCC DOFOR COHESIVE SOIL

FOR PARTIALLY BURIED PIPELINE, ONLY THE

EFFECTIVE BURIED PORTION OF THE DIAMETER IS

USED AND NOT THE FULL DIAMETER.


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IMPACT FORCE

1. SHIP9S ANCHORS

2. FISHING TRAWLS

3. SUBMERGED DEBRIS

SHIPS9 ANCHORS HAVE BEEN NOWN TO IMPACT

PIPELINES BURIED IN E!CESS OF 3. M BELOW THESEAFLOOR.

IF THE PIPELINE CAN NOT BE BURIED AND THE

POTENTIAL FOR FOREIGN BODY IMPACT IS HIGH, THEUSUAL PROCEDURE IS TO INCREASE THE PIPEWALL

THICNESS OR SURROUND THE PIPE WITH PROTECTIVE

ROC.


27/60

FORCE DIAGRAM

1. ELEVATED PIPELINE2. SURFACE OR PARTIALLY BURIED PIPELINE

3. BURIED PIPELINE

RECOMMENDED VALUES OF HYDRODYNAMIC

COEFFICIENTS $DNV 1-1'

HYDRODYNAMIC COEFFICIENTS DEPENDS ON1. REYNOLD9S NUMBER $RE4 U D 6 '

2. EULEGAN " CARPENTER NUMBER $C4 UMT 6 D'

3. PIPE ROUGHNESS $6D'

#. DISTANCE BETWEEN THE PIPE AND THE FI!ED

BOUNDARY $E6D'


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WHERE

D % PIPE DIAMETER E % CLEARANCE BETWEEN THE PIPE AND A

FI!ED BOUNDARY

T % WAVE PERIOD

% ROUGHNESS HEIGHT

U % FLOW VELOCITY

UM % MA!IMUM ORBITAL PARTICLE VELOCITY

% INEMATIC VISCOSITY OF THE WATER

PIPELINE BURIAL FOR STABILITY


29/60

PIPELINE BURIAL FOR STABILITY

BURIED PIPELINES IN SHALLOW WATERS

ACTUAL DEPTH OF BURIAL DEPENDS ON%

1. STORM FREQUENCY

2. IMPORTANCE OF THE PRO(ECT

3. ENVIRONMENTAL CONSEQUENCES OFPIPELINE FAILURE.

PRESENT PRACTICE

1. BURY ALL PIPELINES LOCATED IN WATER DEPTHS

UPTO *) M.

2. *) M IS A PRACTICAL ECONOMICAL LIMIT FOR

THE CONVENTIONAL (ETTING PROCEDURES.


30/60


31/60

BURIED PIPELINES IN DEEP WATERS

1. THE MAGNITUDE OF WAVE " INDUCED LIFT AND

DRAG FORCES IS NEGLIGIBLE.

2. LOO FOR%

DAMAGE FROM SUBAQUOUS SLIDES

TURBIDITY CURRENTS

EROSION

TRAWLING ACTIVITYANCHOR USAGE


32/60

GEOTECHNICAL DATA CAN BE EMPLOYED TO ASSESS THE

BURIAL DEPTH OR TRENCH STABILITY DURING

PIPELAYING OPERATIONS.

VERY IMPORTANT

CRITICAL ASSESSMENT OF THE MARINE ENVIRONMENT

AND SOIL CONDITIONS.

STABILITY CRITERIA WHEN THE SEABED IS PRONE TO


33/60

STABILITY CRITERIA WHEN THE SEABED IS PRONE TO

LIQUEFACTION

1. FULLY AND PARTLY E!POSED PIPELINE

WTOT.P 8 FB FL

PIPELINE IS VERTICALLY INSTABLE

WTOT.P5 FB FLPIPELINE IS STABLE, PROVIDED QSH 8 QRES.SH.ULT

2. BURIED PIPELINE

WTOT.P5 FBPIPELINE IS STABLE, PROVIDED QSH 8 QRES.SH.ULT

WTOT.P8 FB8 WTOT.P WSOIL

PIPELINE IS STABLE, PROVIDED NO LIQUEFACTION


34/60

WTOT.P WSOIL 8 FB

PIPELINE IS STABLE, PROVIDED Q9SH 8 Q9RES.SH.ULT

WHERE

WSOIL % WEIGHT OF OVERBURDENING

SOIL

WTOT.P % WEIGHT OF THE PIPELINE AND

CONTENTS

QSH

OR Q9SH

% SHEAR FORCE IMPARTED TO

SOIL

QRES.SHOR

Q9RES.SH % SHEAR RESISTANCE OF SOIL

DUE TO APPLIED SHEAR FORCE


35/60

EQUILIBRIUM OF PIPELINES IN THE MARINE

ENVIRONMENT

FV 4 FW" FB" FL

FH 4 FD FI" FP" FS" F!

:;< FV 8 FC

=> 6r

FV 8 FO


36/60

FACTOR OF SAFETY

WHY REQUIRED?

1. TO COMPENSATE FOR LOADING CONDITIONS

UNNOWN TO THE DESIGNER

2. UNCERTAINTY IN THE MAGNITUDE OF THE

HYDRODYNAMIC COEFFICIENTS

3. UNFORESEEN EVENTS

THE MINIMUM RECOMMENDED FACTOR OF SAFETY

FOR SUBMARINE PIPELINE IS 1.).


37/60

STABILIZATION METHODS

1. BARE PIPE RESTING ON THE SEA FLOOR

2. BALLASTED PIPE

3. PILE SUPPORTED PIPE

#. PIPE SADDLE

). PIPE ANCHOR *. (ETTED "IN PIPE

+. BURIED PIPE " NATURAL BACFILL

. BURIED PIPE " ARMOR ROC COVER

-. BURIED PIPE " CONCRETE COVER


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Sea bed

Ar@r rBeam

Pile

S/= :/

C>r/ 0


39/60

S/= :/

Tr/> =

(/


40/60

BARE PIPE RESTING ON THE SEA FLOOR

ENVIRONMENTAL CONDITIONS%

1. LESS WAVE AND CURRENT ACTIVITIES

2. SOIL CONDITION PRECLUDE TRENCHING

CONDITIONS TO BE SATISFIED%

1. THE NET DOWNLOAD OF THE PIPE 5 THE

BUOYANCY FORCE

2. THE SOIL STRENGTH MUST BE SUFFICIENT TOPREVENT PIPE FROM SINING INTO OCEAN

FLOOR.

3. THE PIPE WEIGHT ALSO MUST BE SUFFICIENT TO

RESIST BUOYANCY AND SLIDING FORCES.


41/60

MERITS

1. ECONOMICAL

2. EASY TO INSTALL

DEMERITS

1. WILL BE SUB(ECTED TO SCOUR AND

ACCRETION OF SEA FLOOR SEDIMENTS.

2. LIABLE FOR MOVEMENTS DUE TO

MUDFLOW.


42/60

BALLASTED PIPE

ENVIRONMENTAL CONDITIONS

1. MODERATE TO STRONG EFFECT OF WAVES AND

CURRENTS

CONDITIONS AND DESIGN CRITERIA

1. THE ARMOUR ROC MAY BE PARTIAL OR FULLY

COVERED OVER THE PIPELINE, DEPENDS ON

THE INTENSITY OF THE ENVIRONMENTAL

LOADS.

2. IF THE ENVIRONMENTAL LOAD IS LESS, THEN

PARTIAL COVERING IS SUFFICIENT.


43/60

3. IN THIS CASE, THE BUOYANCY AND LIFT FORCE

DUE TO WAVES AND CURRENTS MUST BE

COUNTERACTED BY THE VERTICAL DOWNLOAD

#. THE POSSIBLE HORIZONTAL SLIDING OF THE

PIPE MUST BE TAEN CARE OF BY THE PASSIVE

RESISTANCE OF THE ROC COVER.

). THE THICNESS OF THE CONCRETE COVER

SHOULD BE INCREASED ACCORDING TO THE

ENVIRONMENTAL LOADS $FIG.3B'.

*. THE ARMOUR ROCS MUST BE SIZED TO BE

STABLE AT MA!IMUM WATER PARTICLE

VELOCITIES AND ACCELERATIONS


44/60

MERITS

1. ROCS PROVIDES SOME PROTECTION FROM

FOREIGN BODY IMPACTS

2. SCOUR POTENTIAL IS REDUCED BY THE

PRESENCE OF THE ROC

DEMERIT

1. SPECIAL CARE MUST BE TAEN DURING ROCPLACEMENT TO PREVENT DAMAGE TO THE PIPE.

PILE SUPPORTED PIPE


45/60


1. OCEAN FLOOR HAS INSUFFICIENT BEARINGCAPACITY TO SUPPORT THE PIPE

2. SIGNIFICANT DYNAMIC CHANGES IN THE SEA

FLOOR PROFILE.


1. BUOYANCY AND LIFT FORCE IS COUNTERACTED

BY THE DOWN LOAD OF THE PIPE AND PILE.

2. THE DEPTH OF PENETRATION OF THE PILE AND

ITS SPACING ALONG THE LENGTH OF THE PIPE

SHOULD BE OBTAINED BASED ON THE DESIGN

UPLIFT FORCES


46/60

3. THE HORIZONTAL DRAG AND INERTIA FORCES

WILL BE TRANSFERED THROUGH THE PILES

TO THE SEA BED $FIG.3C'.

DEMERITS

1. VERY E!PENSIVE

2. LARGE QUANTITIES OF DIVER TIME DUE TO

NUMEROUS UNDERWATER CONNECTIONS

3. THE PIPELINE SUSPENDED ABOVE THE OCEAN

FLOOR BETWEEN PIPE BENDS IS SUB(ECTED

VIBRATION FORCES DUE TO VORTE!SHEDDING

#. THE PIPELINE IS E!POSED TO FOREIGN BODY

IMPACT.


47/60

PIPE SADDLE


1. USED IN AREAS WHERE WAVE AND CURRENT

ACTIVITIES ARE MODERATE.


1. THE SADDLES MUST BE DESIGNED TO RESIST THE

OVERTURNING MOMENT CAUSED BY DRAG

FORCES.

2. THE SPACING BETWEEN THE SADDLES ALONG THE

LENGTH IS DETERMINED FOR THE DESIGN

FORCES


48/60

DEMERITS

1. THE PIPELINES SUSPENDED ABOVE OCEAN

FLOOR BETWEEN PIPE SADDLES IS SUB(ECTED TO

VIBRATION FORCES DUE TO VORTE! SHEDDING.

2. THE PIPELINE IS ALSO E!POSED TO FOREIGN

BODY IMPACT


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2. THE IN SITU PULLOUT TESTS OF ANCHORS ARE

TYPICALLY REQUIRED TO VERIFY THE HOLDING

CAPACITY.

DEMERIT

1. E!POSED TO THE FOREIGN BODY IMPACT.

(ETTING IN PIPE


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(ETTING"IN PIPE


1. SANDY SOIL $OR WHEN THE SURFACE

SEDIMENTS ARE EASILY LIQUEFIED BY HIGH

PRESSURE WATER (ETS' $FIG.3F'.

MERIT

1. FORMATION OF TRENCH IS NOT REQUIRED.

DEMERIT

1. CARE MUST BE TAEN DURING (ETTING AND

BURYING OPERATION, SINCE (ETTING SLED CAN

DAMAGE PIPE COATING.


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BURIAL PIPE " NATURAL BACFILL


1. FAST SEDIMENT MOVEMENTS

2. OCEAN SEDIMENT IS ACCEPTABLE AS BACFILL

MATERIAL.

MERIT

1. ECONOMICAL


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DEMERITS

1. POSSIBILITY FOR (ACING UP OF THE PIPE.

2. NATURAL FILL IS WEA IN STRENGTH AND IS

HENCE SUSCEPTIBLE FOR EROSION DURING

SEVERE WAVE ACTIONS.3. POSSIBLE E!POSURE OF THE PIPE AND DIRECT

WAVE ATTAC.

BURIAL PIPE " ARMOUR ROC COVER


54/60

ENVIRONMENTAL CONDITION

1. WAVE CLIMATE IS HOSTILE, LIE SURF ZONES.


1. GOOD QUALITY BEDDING IS PREPARED FIRST ANDPIPE IS LAID ON IT.

2. PIPE IS COVERED WITH QUALITY BACFILL

MATERIALS AND COVERED WITH ARMOURROCS.

3. THE ARMOUR ROC AND THE UNDERLYING

FILTER LAYER MUST BE SIZED TO PREVENT

EROSION OF PIPE BACFILL AND BEDDING

MATERIAL BY WAVE IMPACT.


55/60

MERIT

1. PREVENTS LIQUEFACTION OF THE SOIL,

2. PREVENTS DIRECT WAVE ATTAC ON THE PIPE

$FIG.3H'.

DEMERITS

1. E!PENSIVE.

BURIAL PIPE " CONCRETE COVER


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ENVIRONMENTAL CONDITION

1. E!TREME WAVE FORCES AND FREQUENT

CYCLONE ACTIONS.


1. IT IS IMPORTANT TO PREVENT WASHOUT OF

CEMENT DURING CURING STAGES.

MERITS

1. THE CONCRETE SLAB RECEIVES THE

ENVIRONMENTAL LOADS DUE TO WAVES AND

HENCE THE UNDERLYING PIPELINE IS

PROTECTED $FIG.3I'.


57/60

DEMERITS

1 PLACING UNDERWATER CONCRETE IS A

DIFFICULT PROCESS.

2. THE FUTURE ACCESS TO PIPELINE FOR REPAIR

PURPOSES IS RESTRICTED BY THE CONCRETEBARRIER.

3. THE HARDENING OF THE CONCRETE TOP MAY

INDUCE EROSION OF SEDIMENTS AD(ACENT TOCONCRETE.


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CONCLUSIONS

1. THROUGH UNDERSTANDING OF GEOTECHNICALAND HYDRODYNAMIC CHARACTERS

2. ACCURATE ESTIMATION OF THE DESIGN

ENVIRONMENTAL LOADS

3. LOCATION OF THE PIPE LINE $SURF ZONE OR

OFFSHORE DEEP WATERS'

#. TYPE OF CARGO TO BE TRANSPORTED

$HAZARDOUS OR NON HAZARDOUS'

). FREQUENCY OF CYCLONE EFFECTS


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*. LIFE OF THE PRO(ECT

+. CONSTRUCTION TECHNIQUE

. CAPITAL AND MAINTENANCE COSTS

-. UNDERSTANDING THE MERITS AND DEMERITS OFDIFFERENT STABILIZATION METHODS. A

METHOD SUITABLE FOR ONE SITE MAY NOT BE SUITABLE

FOR OTHER SITES.

1. (UDGMENT BASED ON DETAILED SCIENTIFIC

STUDIES


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pipe stability

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