Ground Screws et alia

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Ground Screws et alia

• Anchors Away
• Craig Griffin
• Bob McLeod

MBOA April 12, 2005
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History

• Original Ground Screws Early 1910s
• A.B.Chance Screw piles developed for relatively
  large structures
• Others companies since
• Manitoba appears to be the home of the lighter
  duty screw pile
• Aspects unique to Manitoba

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The light duty screw pile

• Basic Features
• Typically 8 feet in length
• 4,6,10 as well
• Extensions possible
• Possibly more than one helical plate
• Square or round tube or rod
• Stabilizer near the top
• Increase lateral stability
• Increases load bearing capacity

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Benefits

• Clean. No excavation or excavation removal
• Ideal for areas with limited access
• Limited disruption
• They can function as permanent installations or
  serve as temporary foundations.

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Applications

• Decks
• Sunrooms
• 3 season rooms
• Hot tub support
• Landings, Mud rooms
• Cottages
• Steps
• Fence post (Gate)

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Applications Continued

• Trailer and airplane tie downs
• Similar load capacity (not tested thoroughly)
• Boat docks (experimental)
• Farm applications (storage bins)
• Temporary applications
• Tie backs, retaining wall
• Renovations/Repair
• Large scale examples www.abchance.com

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Decks/Enclosures

• Typical Installation

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Alternative View
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Installation

• Locate point of installation. Slide
  theinstallation wrench over the shaft. Slide
  handle into wrench socket. Turn until tip of the
  shaft is in the ground.
• Two man operation

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Installation continued

• Add a second handle. With oneperson on either
  side, turn the shaft until the top of the shaft
  is at ground level.
• Mechanical options
• Still two man operation
• Torque Important

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Installation continued

• Place stabilizer over the thread andcarefully
  hammer it into the ground.
• This is a very important step.
• Stabilizer Function
• Lateral stability
• Resists torque under load
• Even if Cut and Capped

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Installation continued

• Tighten adjustable nut to topof shaft. Slide
  head over threaded rod. Fasten beam to head.
• Drink Beer

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Anchor w/Wrench

• Clean with little disturbance to yard

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Anchor w/Power Auger

• Courtesy A.B.Chance

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Floating Stabilizer

• There are two significant features of the
  floating stabilizer.
• The stabilizer, in addition to keeping the anchor
  from turning and moving vertically, has a
  floating feature which restricts the shear
  stresses of frost heaves or soil swelling from
  acting on the anchor.
• Thus preventing the anchor from being pulled
  upward from the ground by the forces on the
  stabilizer itself.

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Floating Stabilizer

• The stabilizer is less crucial as the pitch on
  the helical plate is decreased.
• A decreased pitch is also more difficult to
  install if done manually.

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Testing 8 foot one plate

• Test Derived from ASTM
• Locations
• Headingley
• St. Vital
• St. Claude
• Calgary
• Edmonton

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Testing 10 foot two plates

• Test Derived from ASTM D-1143
• Locations
• Headingley

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Soils 3 Bears

• Medium dense sandy gravel very stiff to hard
  silts and clays Too Hard
• Medium dense coarse sand and sandy gravels stiff
  to very stiff silts and clays
• Loose to medium dense fine to coarse sand firm
  to stiff clays and silts Just Right
• Loose fine sand Alluvium loess soft-firm
  clays varied clays fill Too Soft
• Peat, organic silts inundated silts, fly ash

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Loads

• 8 foot anchor 2400 lbs wlt0.035 inch displacement
• (My preference is 2K, 120 lbs/ft2)
• 10 foot anchor 2600 lbs wlt0.01 inch displacement
• Important Note The load is directly related to
  the torque required to screw them in.
• Going in like a hot knife through butter Bad

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Attachments

• Variety of heads

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Difficult Installation

• Example of a mud room on an existing structure,
  enclosed by a deck.
• Removed several deck boards.
• Installed anchor on about a 10 degree angle
• Ground a slot in the anchor just below grade
• Bent the anchor with the wrench, closing the gap.
• No movement to date, no welding deemed necessary.

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Et alia

• More or less it for the anchors or ground screws.
• Next section discusses related products that
  might be found useful.
• Et alia And other things

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Related products

• Deck and Cottage Jacks

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Leveling Existing Structures
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Testing

• Unable to load to failure
• Difficult to adjust under load
• Comparable to telepost
• Beyond 8,000 lbs telepost or cottage jack would
  require an engineered footing. (Check local
  building code)

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Top adjust unit

• More convenient
• Adjusted through deck

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Concrete pad

• Threaded rod is in a hole in the footing.

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Summary

• Overview of ground screws
• Focus on light duty ground screws
• Some cautions
• Importance of stabilizer
• Importance of requisite torque during
  installation
• Related products
• FMI www.anchors-away.ca

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Test

• Typical light load anchor length?
• A) 8 feet
• B) 80 feet
• Purpose of stabilizer?
• A) Resist the anchor screwing itself in
• B) Lateral stability
• C) Both A and B

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Test Continued

• Ideal Soil for light duty anchors
• A) Muck
• B) Manitoba Gumbo
• C) Hardpan
• Anchor goes in like butter
• A) Good
• B) Bad

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Test Continued

• Typical Load Standard 8 foot anchor
• A) 22 lbs
• B) 2200 lbs
• C) 22 million lbs
• When in doubt
• A) Build and check with city later
• B) Check with city then build
• C) Never check with city