Ground Screws et alia

1. Ground Screws et alia Anchors Away Craig Griffin Bob McLeod MBOA April 12, 2005

2. 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

3. 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

4. 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.

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

6. 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

7. Decks/Enclosures • Typical Installation

8. Alternative View

9. 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

10. 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

11. 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

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

13. Anchor w/Wrench • Clean with little disturbance to yard

14. Anchor w/Power Auger Courtesy A.B.Chance

15. 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.

16. 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.

17. Testing: 8 foot one plate • Test Derived from ASTM • Locations: • Headingley • St. Vital • St. Claude • Calgary • Edmonton

18. Testing: 10 foot two plates • Test Derived from ASTM D-1143 • Locations: • Headingley

19. 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

20. Loads • 8 foot anchor: 2400 lbs w<0.035 inch displacement • (My preference is 2K, 120 lbs/ft2) • 10 foot anchor: 2600 lbs w<0.01 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

21. Attachments • Variety of heads

22. 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.

23. 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”

24. Related products • Deck and Cottage Jacks

25. Leveling Existing Structures

26. 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)

27. Top adjust unit • More convenient • Adjusted through deck

28. Concrete pad • Threaded rod is in a hole in the footing.

29. 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

30. 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

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

32. 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