Transcript Slide 1
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 • • • • • • Gas – Pressure Water – Pressure Sewer – Gravity Drainage – Gravity Power – Non-gravity Communications – Non-gravity Trenchless Methods • • • • • • • • 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? • • • • • • Choose the right method Use established “Standards” Collect information/investigate Plan ahead Conduct risk assessments Include mechanisms to handle conflicts Use the Right Method • • • • • • • Open cut Horizontal Directional Drilling Auger boring Pipe ramming Pipe jacking 1996 Microtunneling Tunneling Auger Boring • • • • • • 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 • • • Step 2 • 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 • • • • • • • 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 • • • • • Cobbles or Boulders Wood Fill materials Hard zones Mixed faces 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 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 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 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 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 … • • • • • Cast iron Steel Ductile iron High Density Polyethylene Polyvinylchloride • • • • 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 Quality Assurance & Controls in Specifications Trained Inspectors Testing by Owner Laboratory Final CCTV Inspection of the Installed Pipe Protection of Existing Utilities • • • • • 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