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Introduction to Trenchless Methods

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

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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 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

  3. Types of Infrastructure • Gas –Pressure • Water –Pressure • Sewer –Gravity • Drainage –Gravity • Power –Non-gravity • Communications –Non-gravity

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

  5. Generic Size and Length • Method Size LengthMoling 2” - 12” 150’Ramming 8” - 72” 300’Auger Bore 8” - 60” 250’Pilot Tube 6” - 42” 300’Microtunneling 12” - 108” 1,500’Pipe Jacking >54” 3,000’HDD 2” - 48” 6,500’Tunneling >60” Any length

  6. What to Do? • Choose the right method • Use established “Standards” • Collect information/investigate • Plan ahead • Conduct risk assessments • Include mechanisms to handle conflicts

  7. Use the Right Method • Open cut • Horizontal Directional Drilling • Auger boring • Pipe ramming • Pipe jacking • Microtunneling • Tunneling Pilot Tube 1996

  8. Auger Boring • Road crossings • Cohesive soils • Short distances • Above water table • Need steel casing • Minor steering

  9. 60-inch Diameter SBU-A

  10. Pilot Tube Method • Medium distances • Straight alignments with good accuracy • Variety of soils • Smaller shafts • Moderate equipment costs

  11. Step 1

  12. Step 2

  13. Pilot Tube + “Plus” • Now used as a guide for other method • Auger boring • Pipe Ramming

  14. Pipe Ramming • Wide range of diameters • Soils only • Continuously supported • Typically < 300’ • Above and below water table • Need steel casing • No steering control

  15. Installation Method • Ramming in continuous length or segments

  16. Rammingin Progress

  17. Pilot tube

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

  19. 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

  20. Micro vs Utility Tunneling Remotely operated Precise guidance Pipes jacked from launch pit Continuous support to face Conventional Rib & Lagging Tunnel Microtunnel

  21. Tunnel Shield Construction Lining is built within shield. Lining does not move longitudinally after placement.

  22. Required Axial Thrust versus Length of Drive for Same Diameter

  23. Open Cut What happens happens Trenchless Understand and plan Opposite Approaches

  24. What to Do? • Understand the site history and potential obstructions • Look at old aerial photos • Conduct a geotechnical program • Locate all utilities

  25. Potential Obstructions • Cobbles or Boulders • Wood • Fill materials • Hard zones • Mixed faces

  26. 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

  27. Typical CMP Culverts

  28. 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

  29. Possible Solutions

  30. Consume the Culvert

  31. Use Liner Plate Tunnel

  32. 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

  33. 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)

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

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

  36. Pilot Bore and Tracking Pilot Bore

  37. Drill Bits

  38. Reaming/Hole Enlargement Reaming

  39. Reamers

  40. CLAY ANNULAR SPACE REGION

  41. SAND ANNULAR SPACE REGION

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

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