Introduction to
Trenchless Methods
Presented by
Glenn M. Boyce, PhD, PE
Senior Associates
April 21, 2009
Presentation Objectives
• Provide a better understanding
of trenchless methods used for
new installations
• Learn the advantages and
limitations of the methods
• Discuss contractor
qualifications
Types of Infrastructure
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Gas – Pressure
Water – Pressure
Sewer – Gravity
Drainage – Gravity
Power – Non-gravity
Communications – Non-gravity
Trenchless Methods
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Impact moling
Pipe ramming
Auger boring
Pilot tube
Pipe jacking / Microtunneling
Conventional tunneling
Horizontal directional drilling
Pipe bursting
Generic Size and Length
• Method
Moling
Ramming
Auger Bore
Pilot Tube
Microtunneling
Pipe Jacking
HDD
Tunneling
Size
Length
2” - 12”
150’
8” - 72”
300’
8” - 60”
250’
6” - 42”
300’
12” - 108” 1,500’
>54”
3,000’
2” - 48”
6,500’
>60”
Any length
What to Do?
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Choose the right method
Use established “Standards”
Collect information/investigate
Plan ahead
Conduct risk assessments
Include mechanisms to handle
conflicts
Use the Right Method
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Open cut
Horizontal Directional Drilling
Auger boring
Pipe ramming
Pipe jacking
1996
Microtunneling
Tunneling
Auger Boring
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Road crossings
Cohesive soils
Short distances
Above water table
Need steel casing
Minor steering
60-inch Diameter SBU-A
Pilot Tube Method
• Medium distances
• Straight alignments with good
accuracy
• Variety of soils
• Smaller shafts
• Moderate
equipment costs
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
Pipe Ramming
• Wide range of
diameters
• Soils only
• Continuously
supported
• Typically < 300’
• Above and below
water table
• Need steel casing
• No steering control
Installation Method
• Ramming in continuous length or segments
Ramming
in
Progress
Pilot tube
Pipe Jacking
• Large diameters
• Soils and mixed
ground
• Face supported
• Long distances
• Above the water
table
• Steerable
Microtunneling
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Range of diameters (> 12”)
All ground types
Continuous face support
Long distances
Above or below water table
Range of pipe materials
Steerable to line and grade
Micro vs Utility Tunneling
Remotely operated
Precise guidance
Pipes jacked from launch pit
Continuous support to face
Conventional
Rib & Lagging Tunnel
Microtunnel
Tunnel Shield Construction
Lining is built within shield. Lining does not
move longitudinally after placement.
Required Axial Thrust versus Length
of Drive for Same Diameter
Opposite Approaches
• Open Cut
• Trenchless
• What happens
• Understand
happens
and plan
What to Do?
• Understand the site history and
potential obstructions
• Look at old aerial photos
• Conduct a
geotechnical
program
• Locate all
utilities
Potential Obstructions
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Cobbles or Boulders
Wood
Fill materials
Hard zones
Mixed faces
Typical Machine Sizes
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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
Typical CMP Culverts
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
Possible Solutions
Consume the Culvert
Use Liner Plate Tunnel
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
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)
HORIZONTAL DIRECTIONAL
DRILLING (HDD)
Samuel T. Ariaratnam, PhD, PE
Arizona State University
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
Drill Bits
Reaming/Hole Enlargement
Reaming
Reamers
CLAY
ANNULAR SPACE REGION
SAND
ANNULAR SPACE REGION
Pipe Material Distribution
Underground Construction Magazine
9th Annual Survey, June 2007
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
PIPE BURSTING
Samuel T. Ariaratnam, Ph.D., P.E.
Arizona State University
Pipe Bursting
• Lengths typically 300-600 ft
• Diameters up to 42”
Static Head
Pneumatic Head
• Applications:
– replacement of force mains
– replacement of gravity
sewers
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).
Introduction
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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.”
Applications
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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
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
Static Method (Continuous)
Static Method (Sectional)
Pneumatic Method
Almost all types of pipe can
be burst …
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Cast iron
Steel
Ductile iron
High Density Polyethylene
Polyvinylchloride
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Concrete
Reinforced concrete
Asbestos cement
Clay
STEEL
Various
Host
Materials
VITRIFIED CLAY
CAST IRON
650mm
(26”)
750mm
(30”)
350mm
(14”)
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!
CONTRACTOR QUALIFICATIONS &
PRE-QUALIFICATION
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
Specifications
• Manufacturers
Recommended
Specifications
• Industry/Association
Specification Guidelines
• Project Specific
Testing & Inspection
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Quality Assurance & Controls in Specifications
Trained Inspectors
Testing by Owner Laboratory
Final CCTV Inspection of the Installed Pipe
Protection of Existing Utilities
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Call in Locates
Obtain As-Built Maps (Shared Responsibility)
Mark Utilities (Utility Owners)
Confirm Utilities (Pothole) (Excavator)
Protect (Excavator)
Protection of Existing Utilities –
Locate Marks
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
Logbook/Field Notes
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 Contractor’s
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
Damage Avoidance
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)
Caltrans Inspector Training
Classroom
Field Exercises
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