Installation of Underground

7/28/2019 Installation of Underground

1/74

Installation of UndergroundInstallation of Underground

Services using HDD:Services using HDD:Design ConsiderationsDesign Considerations

By Dr. Samuel T. Ariaratnam, Ph.D., P.Eng.

Arizona State University, USA


2/74

HDD Installation ProcessHDD Installation Process

Pilot Bore Phase

Pullback Phase

Typical Reamers


3/74

Bore Path PlanBore Path Plan should show:

the surface grade line

locations of important surface features

anticipated lateral utility connections and

intersection points

bore depth at each reference point and at critical

points


4/74

Bore Path SelectionBore Path Selection in agreement with:

geometric restrictions and/or requirements

topography

geology

site-specific issues


5/74

Designed Bore ProfileDesigned Bore Profile

recommended:at least one complete length of drill pipe beforestarting to level out the bore path


6/74

BoreplanningBoreplanning SoftwareSoftware


7/74

Entry and Exit AngleEntry and Exit Angle entry angle :

8-16 degrees

determines a set-backdistance of the

machine

exit angle:

5-10 degrees


8/74

Recommended Relationship betweenRecommended Relationship between

Product Diameter and Reamed DiameterProduct Diameter and Reamed Diameter

Diameter of product + 12> 24

Diameter of product x 1.58 24

Diameter of product + 4< 8

Reamed DiameterProduct

Diameter


9/74

Design AspectsDesign Aspects

Essential for successful installation

Allows suitable alignment selection

Can define installation procedures( buoyancy control)

Determines Suitable Equipment Selection

Minimizes Pipe Failure

During Installation

Long term operational (bending)


10/74

BackgroundBackground

Two Publications

Installation Loading and Stress Analysis

Involved with Pipelines Installed by

Horizontal Directional Drilling Form basis of American Gas Association

design guidelines for HDD

Polyethylene Pipe for HorizontalDirectional Drilling

Developed by the Plastic Pipe Institute for

design of HDPE for HDD


11/74

Pipe MaterialPipe Material

Steel Linear Elastic Material

High Tensile strength

High modulus of Elasticity

Large Diameters (>24) except for casings Corrosion and Abrasion Typically Required

High Density Polyethylene Viscoelastic material

Tensile stress & Modulus of Elasticity time,temperature, andduration dependent

Higher resistance to short term loading than long term loading

Duration of loads needs to be considered

Low Modulus of Elasticity & Tensile Stress

5% strain level to prevent long term structural damage


12/74

SOIL COMPARISONSSOIL COMPARISONS

FOR 8 HDPE DR17FOR 8 HDPE DR17

-0.20

0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

0 10 20 30 40 50 60

Bore Path Location (m)

Strain(%)

Clay 1

Clay 2

Sand


13/74

HDPEHDPE

Typical Apparent Modulus of Elasticity (E) Typical Safe Pull Stress

Duration HDPE MDPE Duration HDPE MDPE

Short-term 110,000 psi(800 Mpa)

87,000 psi(600 Mpa)

30 min 1,300 psi(9.0 Mpa)

1,000 psi(6.9 Mpa)

10 hours57,500 psi

(400 Mpa)

43,500 psi

(300 Mpa)60 min

1,200 psi

(8.3 Mpa)

900 psi

(6.2 Mpa)

100 hours51,200 psi

(350 Mpa)

36,200 psi

(250 Mpa)12 hours

1,150 psi

(7.9 Mpa)

850 psi

(5.9 Mpa)

50 years28,200 psi

(200 Mpa)

21,700 psi

(150 Mpa)

24 hours1,100 psi

(7.6 Mpa)

800 psi

(5.5 Mpa)

Apparent Modulus of Elasticity and safe Pull Tensile Stress @ 73oF

(Plastic Pipe Institute, August 1998)

Steel? Modulus of Elasticity = 2.9 X 10

7 psi

? Safe Minimum Yield Strength 30,000 to 50,000 psi


14/74

Pipe Capacity ComparisonPipe Capacity Comparison

SteelSteel

O.D. = 14O.D. = 14

w.t. = 0.25w.t. = 0.25I.D. = 14 - 2(0.25 ) = 13.5I.D. = 14 - 2(0.25 ) = 13.5

O.D. = 14 DR 17O.D. = 14 DR 17

w.t. = 0.82w.t. = 0.82I.D. = 14 - 2(0.82 ) = 12.36I.D. = 14 - 2(0.82 ) = 12.36

HDPEHDPE

Allowable Pull LoadAllowable Pull Load Allowable Pull LoadAllowable Pull Load

= 40,700 lbs= 40,700 lbs

= ( 14= ( 1422 - 12.36- 12.3622 ) 1200psi) 1200psi??44

= 324,000 lbs= 324,000 lbs

= ( 14= ( 1422 - 13.5- 13.522 ) 30,000psi) 30,000psi??44


15/74

Installation Loads andInstallation Loads and

StressesStresses Two Phases

1) Installation

2) Operation

Installation usually governs except inhigh operation pressure conditions

Deep Installation can limit HDPEinstallations


16/74

Installation LoadsInstallation Loads Tension

Frictional Drag

Fluidic Drag Unbalanced Gravity Effects

Bending

External Hoop

Pipe Support Spanning

Pipe Overbend at Entry


17/74

KEY STRESS AREASKEY STRESS AREAS

DURING PULLBACKDURING PULLBACK


18/74


19/74

OperationalOperational Conduit Pressure/Vacuum

Ground Water/ Soil Pressure Key Assumption Stable/Unstable borehole

Live Loads -H2O, Coopers, E80,

nearby structures

Generally small at depths greater than 5 - 10


20/74

Stable boreholes, no side support

Unstable borehole Pipe Arching

GROUNDWATER GROUNDWATER

STABLE BOREHOLE

BOREHOLE

DEFORMATION

SLURRY SLURRY

Borehole DeformationBorehole Deformation(Plastic Pipe Institute, Aug. 1991)(Plastic Pipe Institute, Aug. 1991)


21/74

1 DAY 1 WEEK

2 WEEKS 4 WEEKS

8 HDPE Pipe8 HDPE Pipe


22/74

1 DAY 1 WEEK

2 WEEKS 4 WEEKS

8 HDPE Pipe8 HDPE Pipe


23/74

Summary of 1 Year Digups 8 PipeSummary of 1 Year Digups 8 Pipe

Clay

Sand


24/74

Load CalculationsLoad Calculations

Crossing broken down into straight

line and curved sections.

Loads Determined for:

Net External Loads

Pipe Deflection Unconstrained Buckling

Pullback forces, (Friction, Fluidic,

bending, unbalanced gravity)


25/74

FFTOTALTOTAL = T= TAA + T+ TBB + T+ TCC + T+ TDD + T+ TEE + T+ TFF

Horizontal Directional Drill ProfileHorizontal Directional Drill Profile(Huey et al, 1996)(Huey et al, 1996)


26/74

Net External LoadsNet External Loads Stable Borehole

PNET = PMUD - PI

Unstable BoreholePNET = PE + PGW + PLIVE - PI

P = H


27/74

Pipe DeflectionPipe Deflection

Buoyancy

Earth Load

For HDPE pipe, care needs to be utilized onselecting an appropriate E. Conservative islong term values.

Deflection generally minor on steel pipe

4

=EI

0.1169

2

D

D

3

=E

0.0125 PE

D

12 (DR-1)


28/74

Unconstrained BucklingUnconstrained Buckling

Uniform external pressure results incompressive hoop stress

For HDPE

For Steel

fo = ovality factor (0.4 for 7.5% deflection)

fr = tensile reduction factor

if pipe is constrained by soil or grout fr is replaced by

fs (grout enhancement factor) which is approximately 5 for grout

? = Poissons ratio

D

tPALLOW = 0.88 E

2

2t

Pnet Dfn =

DR-1

1PALLOW =(1 - u2 )

2Efo fr

3


29/74

Buckling for HDPEBuckling for HDPE

During PullbackDuring Pullback

14 HDPE DR 17

= 9.8 psi

17-1

1PALLOW =

( 1 - 0.352 )

2 ( 55,000psi )(0.4) (0.8)

3


30/74

P = h

= 17.5ft of drilling fluid head

if water utilized to counteract external pressure

h =P

=9.8psi ( 144 )in2

80 lbs ft3

ft2

h =9.8psi ( 144 )in2

80 - 62.4

ft2= 80ft


31/74

Pull Back ForcePull Back Force

Main component is pullback forces

Determined in straight line and

curved sections

Consists of:Friction

FluidicUnbalanced Gravity

Bending


32/74

Straight Section ModelStraight Section Model(Huey et al, 1996)(Huey et al, 1996)

T1

T2

N2DRAG

L

frict

0

WsL


33/74

Pull Back ComponentsPull Back Components

Buoyancy has significant effect on Ws

0.25 - 0.40usoil

FTOTAL = Ffrict + Fdrag + Ws L Sin 0

Unbalanced Weight EffectsFweight = Ws Sin 0 L* *

?

Fluidic Drag

Fdrag = 12 D L umud* * * *

* * Friction

Ffrict = Ws L Cos ? usoil*


34/74

Buoyancy EffectsBuoyancy Effects

No buoyancyNo buoyancy

Pipe WeightPipe Weight = 14.9 lbs / ft= 14.9 lbs / ft

NET ( Ws )NET ( Ws ) = 70.6 lbs / ft= 70.6 lbs / ft

14 DR 17 HDPE14 DR 17 HDPE

Weight = 14.9 lbs / ftWeight = 14.9 lbs / ft Mud Weight =Mud Weight = mudmud = 80 lbs / ft= 80 lbs / ft

33

== 85.585.5 lbslbs/ ft/ ftBuoyancyBuoyancy == mudmud = ( )2 80 lbslbs / ft/ ft 23

??

44

12121414DD2

?

44


35/74

Buoyancy - Water Utilized in PipeBuoyancy - Water Utilized in Pipe

For 400 ft BoreFor 400 ft Bore

85.5 - 14.9 - 52.085.5 - 14.9 - 52.0 = 18.6 lbs / ft= 18.6 lbs / ftNET ( Ws ) =NET ( Ws ) =

14 DR 17 HDPE I.D. = 12.3614 DR 17 HDPE I.D. = 12.36

(( ))22 62.462.4 lbslbs / ft/ ft33??

441212

12.3612.36 = 52.0 lbs / ft= 52.0 lbs / ftWeight of Water =Weight of Water =

F no buoyancy =F no buoyancy = ( 70.6 lbs / ft )( 400 ft )( 0.3 )( 70.6 lbs / ft )( 400 ft )( 0.3 ) = 8,470 lbs= 8,470 lbs

F buoyancy =F buoyancy = ( 18.6 lbs / ft )( 400 ft )( 0.3 )( 18.6 lbs / ft )( 400 ft )( 0.3 ) = 2,230 lbs= 2,230 lbs


36/74

T1

N

N2

N1

WsL

frict

frict2

frict1DRAG

01

02

a

R

Curved Section ModelCurved Section Model(Huey et al, 1996)(Huey et al, 1996)


37/74

BendingBending Steel

Modelled as 3 point bending and is complex

and iterative

HDPE

Not an issue as safe bending stress (?40D) is

much less than typical drill curve radii of 300

ft or more (i.e. drill rod limiting)

Forces calculated using cable laying formula

Fcurve = e?? (? soilWBL)


38/74

Stress AnalysisStress Analysis Once all loads are calculated, stress

analysis is undertaken to ensure allowable

stresses are not exceeded.

Highest stress will typically occur wherebending, tension and external/internalpressure act together.

Loads to be looked at individually and incombination.


39/74

Effect of CollapsedEffect of Collapsed

Borehole on Pipe FrictionBorehole on Pipe Frictionand Loadand Load

GROUNDWATER GROUNDWATER

STABLE BOREHOLEBOREHOLE

DEFORMATION

SLURRY SLURRY


40/74

Stable BoreholeStable Borehole

F frict = Ws L Cos ?? soil

= (70.6 lbs)(400 ft)(0.3) =8,470 lbs

F drag = 12? D L ? mud

= 12? (14 )(400 ft)(0.05) =10,555 lbs

F total = 8,470 + 10,555= 19,000 lbs

Ffrict

Fdrag


41/74

Unstable BoreholeUnstable Borehole

Assume 30% of length collapse

Frict = (70.6 lbs)(280 ft)(0.3) =5,930 lbs

F drag,collapse = 12? (14 )(120 ft )(0.3) =19,000 lbs

F drag = 12? (14 )(280 ft)(0.05) =7,390 lbs

F total = 32,320 lbs

Frict


42/74

Always Have A Plan!Always Have A Plan!

Contractors

Contingency Plan

Engineers Plans

and Specs


43/74

Bore Tracking and EquipmentBore Tracking and Equipment


44/74

IntroductionIntroduction Two categories of tracking methods

Walkover systems

Non-walkover systems

Operate best in interference-free environment

(active vs. passive interference)

Drill locator is responsible for ensuring that thebore follows the design profile


45/74

InterferenceInterference A log book containing drill pipe number,

pitch, depth, steering commands, apparent

underground obstructions, and groundconditions is recommended

Brief inconsistencies in depth may be

effectively overcome through the use of pitchreadings and calculations


46/74

Interference Cont.Interference Cont. Drill locator is responsible for recognizing the

limitations of the equipment and

inconsistencies in readings If problems arise, the bore should be stoppeduntil identified and corrected

Should walk the bore path with the receiver onprior to boring operators to assess potentialinterferences


47/74

Active InterferenceActive Interference

Can cause the following:

Erratic signal strength and depth readings

Loss of pitch and roll data

Inaccurate receiver calibration, leading to depth

errors

May be caused by anything that emits a signal or

generate its own magnetic field


48/74

Examples of ActiveExamples of Active

InterferenceInterference Buried power lines

Traffic light power loops

Microwave towers

Invisible dog fences

Airport landing systems

Security systems

Fiber line traces


49/74

Passive InterferencePassive Interference

Can cause the following:

Depth may appear greater than they actually are

All information may be blocked Drill head position may be incorrect

May be caused by anything that blocks, absorbs,

or distorts a magnetic field


50/74

Examples of PassiveExamples of Passive

InterferenceInterference Metals fences

Re-bar in concrete

Electronic ignitions from cars

Buried metal

Salt water

Military operations


51/74

Walkover Tracking SystemsWalkover Tracking SystemsConsists of three main components:

Transmitter (beacon or sonde)

Hand held receiver

Optional remote monitor


52/74

TransmitterTransmitter

Emits a continuous magnetic signal at a

predetermined frequency

Ability to overcome interference is

related to its frequency and signal

strength

Available for depths up to 140 ft.


53/74

ReceiverReceiver

Displays signals sent by

the transmitter in numeric

or graphic form Depth (ft. or m)

Roll or clock position of the

steering face or bent sub

Pitch (% of slope ordegrees)

Accuracy ranges of2%

to 5% of depth


54/74

Remote MonitorRemote Monitor

Not essential to the drillingoperation

However, reduces drilling

time by providing the drilloperator with informationrequired to position andinterpret the reaction of thedrill head to the steering and

drilling conditions Some provide a graphical

representation of theprogression of the bore


55/74

Bore Mapping SystemsBore Mapping Systems

Built into the remote display of walkoverlocating systems and stores:

Entry and exit locations and angles

Depth and pitch Bend radius

Alignment

Topographical (surface) elevations

Known surface and subsurface obstacles Transmitter temperature and battery status

Time between data entries

Drill pipe number

Drill head location


56/74

As-As-BuiltsBuilts/Operator Logs/Operator Logs

HDD Contractor is responsible formarking the plans to indicate any and allvertical and horizontal deviations between

the design and actual bore Operator logbook should be maintained

and updated daily by the Drill Locator orSuperintendent and should include

Pipe number, depth, pitch, steeringcommands, and notes


57/74

Home to Target SystemsHome to Target Systems

Enables the drill locator to program the

receiver to direct the transmitter to aspecified location at a given pitch

Beneficial in situations where the drill locator

is unable to physically track the progress of

the bore from the drill head


58/74

DESIGN OF DRILLINGDESIGN OF DRILLINGFLUIDSFLUIDSDr. Samuel T. Ariaratnam, Ph.D.,

P.Eng


59/74


60/74


61/74


62/74


63/74


64/74


65/74


66/74


67/74


68/74


69/74


70/74


71/74


72/74


73/74


74/74

Documents

Installation of Underground