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Introduction to Trenchless Methods

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1 Introduction to Trenchless Methods
Presented by Glenn M. Boyce, PhD, PE Senior Associates Notes to Instructor: (Slide #1) This training module is the first one. The module is intended to provide a brief/general introduction of the different trenchless methods to be covered by this short course. It is important to define “trenchless” and the available methods. Need to mention that open cut/trenching is an acceptable method as well. The following slides will provide introductory material and provide a foundation for the course. Also discuss the agenda for the course and topics to be covered. April 21, 2009

2 Presentation Objectives
Provide a better understanding of trenchless methods used for new installations Learn the advantages and limitations of the methods Discuss contractor qualifications Notes to Instructor: (Slide #2) Discuss the course objectives. Walk through the course agenda. A key objective to emphasize is understanding the advantages and limitations of the various trenchless methods.

3 Types of Infrastructure
Gas – Pressure Water – Pressure Sewer – Gravity Drainage – Gravity Power – Non-gravity Communications – Non-gravity Notes to Instructor: (Slide #5) Explain that some lines are under pressure like drinking water and gas. These pipelines do not have specific grade requirements. Gravity systems – specifically sewers (wastewater and storm water) flow by gravity and have grade requirements. Wastewater for example involves moving solids and have minimum grade requirements to maintain flow velocities in the pipe. Most pipelines must remain within corridors or rights-of-way and therefore have alignment (line) requirements.

4 Trenchless Methods Impact moling Pipe ramming Auger boring Pilot tube
Pipe jacking / Microtunneling Conventional tunneling Horizontal directional drilling Pipe bursting Notes to Instructor: (Slide #6) Briefly discuss the various trenchless methods. The list is basically from smallest to largest with horizontal directional drilling (HDD) listed last as it is a “pulling method” versus a “pushing method.”

5 Generic Size and Length
Method Size Length Moling 2” - 12” ’ Ramming 8” - 72” ’ Auger Bore 8” - 60” ’ Pilot Tube 6” - 42” ’ Microtunneling 12” - 108” 1,500’ Pipe Jacking >54” 3,000’ HDD 2” - 48” 6,500’ Tunneling >60” Any length Notes to Instructor: (Slide #9) Provide this table to discuss the typical size ranges for the different methods. Also discuss the typical lengths of installations. Note that man-entry methods typically begin at 48 inches and larger. That you need some size to get into the pipe and room to work. Mention that the industry is continuing to develop and change. The size ranges are increasing. Drive lengths are increasing every 6 months or so. Also note that while the drive lengths are increasing – it does not mean you need to set world records every time the method is used. In fact, managing risk means not exceeding the typical drive lengths. The instructor may need to update this slide on occasion.

6 What to Do? Choose the right method Use established “Standards”
Collect information/investigate Plan ahead Conduct risk assessments Include mechanisms to handle conflicts Notes to Instructor: (Slide #11) Choosing the right method for the project will eliminate 90% of the problems that can go wrong on a project. The wrong method for a project will likely lead to schedule delays and extra cost. There are established “standards” / guidelines to help select the best method for the project. You need to collect information and do your homework. Plan ahead. Know what are the risks on the project before you start construction. Hire an experienced engineer with trenchless experience to review the design and help eliminate known problems. Maintain a dialog with the contractor.

7 Use the Right Method Open cut Horizontal Directional Drilling
Auger boring Pipe ramming Pipe jacking Microtunneling Tunneling Notes to Instructor: (Slide #12) There are a number of different methods available. Remember that open cut/trenching may be the right method. ASCE published a Manual of Practice #89 in It discusses many of the methods listed. One method not discussed is the pilot tube method. The reason is the pilot tube method has evolved since the book was published. Remember new methods continue to develop and evolve. It is important to remain current with the various methods available. Pilot Tube 1996

8 Auger Boring Road crossings Cohesive soils Short distances
Above water table Need steel casing Minor steering Notes to Instructor: (Slide #14) Auger boring is one of the older trenchless methods. With an auger and casing, the pipe can be installed by pushing the pipe/casing into the ground while removing the ground/earth with the auger. Auger boring, also known as “jack and bore”, was traditionally used for road crossings. First done in soils, mostly clayey material, the advancement of bigger engines with higher torque now allows auger boring to be used in rock. The method is typically used above the groundwater table. There are a lot of small-size contractors who have auger boring equipment. Until recently, auger boring has had only minor steering ability. Auger boring is now being combined with pilot tube to make the method steerable.

9 60-inch Diameter SBU-A Notes to Instructor: (Slide #50) 60 inch diameter SBU-A. Blue pads are steering jacks.

10 Pilot Tube Method Medium distances
Straight alignments with good accuracy Variety of soils Smaller shafts Moderate equipment costs Notes to Instructor: (Slide #15) The pilot tube method was first developed to install sewer laterals from manholes. A small diameter “pilot” tube is pushed into the ground. The orientation/direction of the tube’s head is monitored with a camera looking down the center of the tube. The tube is installed at a precise line and grade. Once the pilot tube reaches the receiving shaft, the pilot phase of the installation is complete. With sewer laterals, the same size or slightly larger pipe is then pushed in behind the pilot tube – using the pilot tube as a guide. Contractors realizing the method could be used on the main line sewer installation as well, began using the pilot tube method to install 6-inch, 8-inch, 10-inch, and 12-inch sewer lines. With experience and success on projects, contractors began using the pilot tube method to install longer drives – from 100 feet to 250 feet, 350 feet, and now up to 500 feet. And the diameters have increased as well. With two and three passes / phases, diameters of 18-inch, 24-inch, 36-inch, up to 42-inch are now installed. The amount of equipment is minimal. Shafts are typically smaller than required for other trenchless methods.

11 Step 1 Notes to Instructor: (Slide #16) Installation of the Pilot Tube to line and grade. The drill is steered by rotating the drill tip to achieve directional control.

12 Notes to Instructor: (Slide #17) This is a head on picture looking down the drill steel to the pilot tube jacking frame.

13 Notes to Instructor: (Slide #18) This is a picture of the steering lights in the battery casing. This assembly is installed immediately behind the drill tip.

14 Notes to Instructor: (Slide #19) The control LED’s as seen on the monitor. Operating information is on the right.

15 Step 2 Notes to Instructor: (Slide #20) Enlarge the hole, excavate, while retrieving the pilot drill steel at the receiving shaft. The hole is continuously supported.

16 Pilot Tube + “Plus” Now used as a guide for other method Auger boring
Pipe Ramming Notes to Instructor: (Slide #21) It was only time until the contractors realized that if you combined the accuracy of the pilot tube to set line and grade with the bigger engines to turn the augers, that auger boring could now be used to install pipes at precise line and grade. As shown in the picture, the pilot tube equipment is used to install a pilot tube as a guide for the auger boring equipment. The pilot tube is now also used as a guide for pipe ramming. The two methods combined utilize the advantages of each construction method.

17 Pipe Ramming Wide range of diameters Soils only Continuously supported
Typically < 300’ Above and below water table Need steel casing No steering control Notes to Instructor: (Slide #22) Pipe ramming has evolved from conventional pile driving (turned horizontal), impact moles, and piercing tools. Small air hammers were attached to open pipe. The pipe is driven into the ground, displacing only the pipe’s wall thickness. The method provides continuous face support because no material is excavated. Once the pipe is installed, the center of the pipe is cleaned out and the pipe installation is complete. The same process is used today, but the air hammers are larger and provide a greater amount of energy to the pipe. The pipe is placed on guide rails to launch with the intended slope. Pilot tubes are now used to provide greater line and grade control. The construction method provides continuous support and can be low cost.

18 Installation Method Ramming in continuous length or segments
Notes to Instructor: (Slide #9) The hammer drives the casing into the ground, casing pipe segments are added until the casing exits, and the spoils are removed from inside the casing. The hammer may require support to prevent tipping the casing.

19 Ramming in Progress Notes to Instructor: (Slide #44) When ramming, the contractor should be recording advance rate, say at 5 minute increments, including operating parameters like psi, cfm, and blows per minute for understanding the current project and for future project planning.

20 Pilot tube Notes to Instructor: (Slide #23) The set up with the pilot tube (red arrow) installed to line and grade. Note dewatering wells and sloughing behind steel plate lagging.

21 Pipe Jacking Large diameters Soils and mixed ground Face supported
Long distances Above the water table Steerable Notes to Instructor: (Slide #24) Talk about pipe jacking. The system involves personnel entry. A shield is used to create a supported work space. Face support is needed depending on the ground conditions. The type of face support will vary. The ground is excavated in front of the shield. The shield is advanced through the ground with the pipe that is jacked into place. The advance rate is relative to the speed of excavation and jacking. The size is large enough that long distances can be completed between shafts.

22 Microtunneling 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 Notes to Instructor: (Slide #25) Microtunneling is like pipe jacking except the cutting face can provide continuous support during excavation by using slurry. The use of slurry is useful when advancing pipe below the groundwater table. Microtunneling is also remotely control, so the size of the pipe is not limited. Smaller diameter microtunneling machines still exist, but new projects requiring small diameters could end up using the pilot tube method. Microtunneling with slurry machines are typically used for the larger diameters in the 48-, 54-, 60-, 66-, 72-, 84-, and 96-inch range.

23 Micro vs Utility Tunneling
Remotely operated Precise guidance Pipes jacked from launch pit Continuous support to face Notes to Instructor: (Slide #26) Pipe jacking and microtunneling are similar to conventional tunneling. Instead of jacking pipe as the tunnel lining, a lining system can be installed as the shield is advanced, eliminating shafts and increasing drive lengths. Conventional tunneling should be considered when pipe jacking and microtunneling are possible construction methods. Conventional Rib & Lagging Tunnel Microtunnel

24 Tunnel Shield Construction
Notes to Instructor: (Slide #27) Discuss the difference between tunneling and pipe jacking. Use this figure to discuss the differences. In tunneling, the machine/shield pushes off the tunnel lining directly. There is less jacking force needed. In pipe jacking and microtunneling, the jacks are made from behind the shield to the (jacking) shaft. By pushing the pipe, the machine/shield is advanced. The jacking forces will be higher because we are pushing the shield and the pipe string. Tunneling can go longer distances between shafts. Lining is built within shield. Lining does not move longitudinally after placement.

25 Required Axial Thrust versus Length of Drive for Same Diameter
Notes to Instructor: (Slide #28) This figure shows the jacking forces (axial thrust) of pipe jacking and tunneling. The forces are divided into two components. Face pressure, which remains constant, needs to be countered with tunneling or pipe jacking. Pipe friction increases with drive length. Since tunneling is not pushing pipe into the ground, the loads are lower and constant (face pressure only). Tunnels can be advanced for long distances without stopping, unlike pipe jacking.

26 Opposite Approaches Open Cut What happens happens Trenchless
Understand and plan Notes to Instructor: (Slide #30) Start the discussion by explaining that trenchless methods are different than open cut. Most (all) owners and engineers are familiar with using open cut methods to install utilities. It is done all the time. When using open cut methods, the owner can let the contractor dig the trench. The subsurface conditions are what they are. The contractor will expose and see the subsurface ground conditions and utilities. They will adopt their excavation methods to the ground encountered. They will work around the utilities. No geotechnical investigations are typically needed. Many times, if borings are drilled in advance of construction, the borings are not shared with the contractor. Using trenchless methods on the other hand requires more planning and understanding of the subsurface conditions. The ground conditions will not be exposed. Much of the ground will not be seen. The only information available will be from the geotechnical investigations and the collection of information from past projects. Design of a trenchless project means collecting information, understanding the potential impacts to the proposed work, and sharing that information with the contractor. These opposite approaches should be discussed. Emphasize the need to “understand the subsurface conditions.”

27 What to Do? Understand the site history and potential obstructions
Look at old aerial photos Conduct a geotechnical program Locate all utilities Notes to Instructor: (Slide #32) Discuss the steps to follow to collect the needed information. Emphasize the need to understand the site history? What was here before? How did the material at the site get there? By floods – looks for boulders and cobbles. Was fill imported to build the road embankment? Where did the fill come from? What is in the fill? Mention that old aerial photos provide many clues as to a site history? Tax records/property maps exist for most area starting in the 1900’s or sooner. Early aerial photos were taken in the 1930s. Develop a geotechnical investigation program based on the information collected above. Do a utility search and survey? Contact the local utility companies for information. Walk the site and look for cover plates and other telltales.

28 Potential Obstructions
Cobbles or Boulders Wood Fill materials Hard zones Mixed faces Notes to Instructor: (Slide #33) Understanding what potential obstructions can be in front of the advancing face could mean success or stoppage. Some methods are better equipped to deal with specific types of obstructions. Cobbles and boulders are typically harder than the surrounding soils. Being able to advance through soil may not be equal to advancing through rock pieces. Wood is fibrous and becomes stringy as shown in the photograph. Hard zones can stop the advancing face of the machine / shield. Mixed zones between soil and rock can also create problems, and should be understood and addressed during design.

29 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 Notes to Instructor: (Slide #39) This slide outlines the typical size ranges of the various trenchless methods used in the industry. Walk through the list and compare the size ranges. Mention that size ranges do increase over time. Mention pilot tube is now been used to install 42-inch diameter pipe. The instructor may need to update this slide on occasion.

30 Typical CMP Culverts Notes to Instructor: (Slide #40)

31 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 Notes to Instructor: (Slide #41) Walk through each bullet on this slide. This slide is the end of Training Module 1.

32 Possible Solutions Notes to Instructor: (Slide #42)

33 Consume the Culvert Notes to Instructor: (Slide #43)

34 Use Liner Plate Tunnel Notes to Instructor: (Slide #44)

35 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 Notes to Instructor: (Slide #45)

36 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) Notes to Instructor: (Slide #46) Walk through each bullet on this slide. This slide is the end of Training Module 1.

Samuel T. Ariaratnam, PhD, PE Arizona State University

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

39 Pilot Bore and Tracking


41 Drill Bits


43 Reaming/Hole Enlargement

44 Reamers



47 Pipe Material Distribution
Underground Construction Magazine 9th Annual Survey, June 2007












59 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

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

61 Pipe Bursting Lengths typically 300-600 ft Diameters up to 42”
Applications: replacement of force mains replacement of gravity sewers Static Head Pneumatic Head

62 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).

63 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.”

64 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

65 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

66 Static Method (Continuous)

67 Static Method (Sectional)

68 Pneumatic Method

69 Almost all types of pipe can be burst …
Cast iron Steel Ductile iron High Density Polyethylene Polyvinylchloride Concrete Reinforced concrete Asbestos cement Clay

70 Various Host Materials

71 650mm (26”) 750mm (30”) 350mm (14”)

72 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!


74 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

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

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

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

78 Protection of Existing Utilities – Locate Marks

79 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

80 Logbook/Field Notes

81 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

82 Damage Avoidance

83 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 (

84 Caltrans Inspector Training
Classroom Field Exercises

85 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

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