Introduction to Trenchless Methods

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Introduction to Trenchless Methods
Presented by Glenn M. Boyce, PhD, PE Senior
Associates
April 21, 2009
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Presentation Objectives

• Provide a better understanding of trenchless
  methods used for new installations
• Learn the advantages and limitations of the
  methods
• Discuss contractor qualifications

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Types of Infrastructure

• Gas Pressure
• Water Pressure
• Sewer Gravity
• Drainage Gravity
• Power Non-gravity
• Communications Non-gravity

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Trenchless Methods

• Impact moling
• Pipe ramming
• Auger boring
• Pilot tube
• Pipe jacking / Microtunneling
• Conventional tunneling
• Horizontal directional drilling
• Pipe bursting

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Generic Size and Length

• Method Size LengthMoling 2 - 12
  150Ramming 8 - 72 300Auger Bore 8 -
  60 250Pilot Tube 6 - 42
  300Microtunneling 12 - 108 1,500Pipe
  Jacking gt54 3,000HDD 2 - 48
  6,500Tunneling gt60 Any length

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What to Do?

• Choose the right method
• Use established Standards
• Collect information/investigate
• Plan ahead
• Conduct risk assessments
• Include mechanisms to handle conflicts

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Use the Right Method

• Open cut
• Horizontal Directional Drilling
• Auger boring
• Pipe ramming
• Pipe jacking
• Microtunneling
• Tunneling

Pilot Tube
1996
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Auger Boring

• Road crossings
• Cohesive soils
• Short distances
• Above water table
• Need steel casing
• Minor steering

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60-inch Diameter SBU-A
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Pilot Tube Method

• Medium distances
• Straight alignments with good accuracy
• Variety of soils
• Smaller shafts
• Moderate equipment costs

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Step 1

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Step 2

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Pilot Tube Plus

• Now used as a guide for other method
• Auger boring
• Pipe Ramming

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Pipe Ramming

• Wide range of diameters
• Soils only
• Continuously supported
• Typically lt 300
• Above and below water table
• Need steel casing
• No steering control

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Installation Method

• Ramming in continuous length or segments

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Rammingin Progress
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Pilot tube
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Pipe Jacking

• Large diameters
• Soils and mixed ground
• Face supported
• Long distances
• Above the water table
• Steerable

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Microtunneling

• Range of diameters (gt 12)
• All ground types
• Continuous face support
• Long distances
• Above or below water table
• Range of pipe materials
• Steerable to line and grade

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Micro vs Utility Tunneling
Remotely operated Precise guidance Pipes jacked
from launch pit Continuous support to face
Conventional Rib Lagging Tunnel
Microtunnel
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Tunnel Shield Construction
Lining is built within shield. Lining does not
move longitudinally after placement.
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Required Axial Thrust versus Length of Drive for
Same Diameter
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Opposite Approaches

• Open Cut
• What happens happens

• Trenchless
• Understand and plan

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What to Do?

• Understand the site history and potential
  obstructions
• Look at old aerial photos
• Conduct a geotechnical program
• Locate all utilities

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Potential Obstructions

• Cobbles or Boulders
• Wood
• Fill materials
• Hard zones
• Mixed faces

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Typical Machine Sizes

• Piercing 2 to 3 inches
• Pilot Tube 6 to 36 inches
• HDD 6 to 54 inches
• Auger Boring 10 to 60 inches
• Pipe Jacking/MT 12 to 96 inches
• Pipe Ramming 12 to 144 inches
• Shield 60 to 144 inches

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Typical CMP Culverts
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Replacement Issues

• Need to increase size for aquatic passage
• Must keep existing culvert active during
  construction
• Minimize costs
• Develop the best cross section
• Use the right materials

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Possible Solutions
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Consume the Culvert
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Use Liner Plate Tunnel
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Design Solutions

• Built a parallel pipe barrel
• Increases capacity
• Allow the existing to remain in service
• Get to use the materials you want
• Slipline the existing after new
• Built a new entry and exit apron

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Closing Thoughts

• Methods still evolving
• Many hybrid methods emerging
• Better alignment control emerging in auger
  boring applications
• Must identify potential obstructions (or get
  X-ray vision)

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HORIZONTAL DIRECTIONAL DRILLING (HDD)
Samuel T. Ariaratnam, PhD, PE Arizona State
University
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Background

• Lengths up to 8,400 feet
• Diameters of 2 54
• Applications
• Utility conduits
• Pipelines
• Gravity sewers
• Force mains
• Horizontal remediation wells
• Geotechnical investigations

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Pilot Bore and Tracking
Pilot Bore
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Drill Bits
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Reaming/Hole Enlargement
Reaming
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Reamers
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CLAY
ANNULAR SPACE REGION
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SAND
ANNULAR SPACE REGION
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Pipe Material Distribution
Underground Construction Magazine 9th Annual
Survey, June 2007
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Conclusions

• HDD is a minimally-intrusive trenchless
  construction method suited for highly congested
  urban areas and high traffic zones
• Horizontal Directional Drilling equipment is
  capable of installing a wide range of utilities
• HDD will never replace traditional open-cut
  methods however, they complement each other

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PIPE BURSTING
Samuel T. Ariaratnam, Ph.D., P.E. Arizona State
University
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Pipe Bursting

• Lengths typically 300-600 ft
• Diameters up to 42
• Applications
• replacement of force mains
• replacement of gravity sewers

Static Head
Pneumatic Head
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Common Types of Bursting Systems
Pneumatic Systems - Usually include a pneumatic
tool and winch and bursts the pipe using the
kinetic energy of the tool. The pipe is usually
attached to either the burst head or tool.
Static Systems Usually include a hydraulic
power source and a rod shuttling system and use
high tonnage to pull new line into place.
Small Portable Systems - Either pneumatic or
static for doing small diameter and short runs
(e.g. laterals).
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Introduction

• Emerging field of pipe replacement
• Replacement of the host pipe by fragmenting the
  existing conduit and installing a completely new
  pipe of equal diameter or larger in its place.

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Applications

• Total pipe replacement
• Typical upsize as much as 20 30
• Industrial Municipal - Main Line Laterals
• Various host and product pipe materials
• Continuous or Sectional pipe installation

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Pipe Bursting Feasibility

• May achieve lower costs compared to open trench
• Less construction time
• Minimal excavation
• Social cost savings
• Reduces ground settlement
• Low environmental impact

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Static Method (Continuous)
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Static Method (Sectional)
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Pneumatic Method
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Almost all types of pipe can be burst

• Cast iron
• Steel
• Ductile iron
• High Density Polyethylene
• Polyvinylchloride

• Concrete
• Reinforced concrete
• Asbestos cement
• Clay

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Various Host Materials
VITRIFIED CLAY
STEEL
CAST IRON
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650mm (26)
750mm (30)
350mm (14)
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Conclusions

• Pipe bursting is the only trenchless method
  capable of installing a new pipe of equal or
  larger diameter as a replacement option
• Almost any type of existing pipe can be burst and
  replaced with most pipe materials
• Proper planning is critical to project success!

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CONTRACTOR QUALIFICATIONS PRE-QUALIFICATION
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Introduction

• The majority of trenchless contractors are
  reliable and follow good installation practices
• However, agencies must be aware of those few
  cowboy contractors
• Qualifying contractors is a recommended practice
  for trenchless projects to ensure use of
  competent contractors

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Specifications

• Manufacturers Recommended Specifications
• Industry/Association Specification Guidelines
• Project Specific

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Testing Inspection

• Quality Assurance Controls in Specifications
• Trained Inspectors
• Testing by Owner Laboratory
• Final CCTV Inspection of the Installed Pipe

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Protection of Existing Utilities

• Call in Locates
• Obtain As-Built Maps (Shared Responsibility)
• Mark Utilities (Utility Owners)
• Confirm Utilities (Pothole) (Excavator)
• Protect (Excavator)

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Protection of Existing Utilities Locate Marks
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As-Builts, Operator Logs, Notes

• Contractor is responsible for marking the plans
  to indicate any and all vertical and horizontal
  deviations between the design and actual
  installation
• Operator logs/notes should be maintained and
  updated daily by the Contractor and should
  include
• Pipe number, depth, pitch, steering commands, and
  notes

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Logbook/Field Notes
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Contractor Submittals

• Proof of success on prior similar projects
• Pipe material, diameter, length
• Make/model of equipment, guidance equipment,
  fluid mixture
• Slurry disposal plan
• Contingency plan
• Safe plan and protocols
• Certification by the manufacturer that the
  Contractors personnel are trained in the use of
  the equipment
• Training certification for pipe installation
• Fusion training certification for HDPE
• Construction Plan Installation Schedule
• Traffic Control Plan

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Damage Avoidance
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Trenchless Training Courses

• Horizontal Directional Drilling Good Practices
• Pipe Bursting Good Practices
• New Installation Methods Good Practices
• Cured-in-Place Pipe (CIPP) Good Practices
• Sewer Laterals Rehabilitation Replacement

(www.nastt.org)
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Caltrans Inspector Training
Classroom
Field Exercises
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Conclusions

• Well-written specifications are important to
  minimize claims
• Hiring a competent contractor can be achieved
  through pre-qualification
• There are numerous available trenchless
  technology options