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Revision A November 2021
Appendix C: Encountering Rock
Assembling Foundation Tubes or Posts when Encountering Rock
Foundation Tubes
Complete the following steps to assemble foundation tubes when encountering rock:
1. Select Option A or Option B below when encountering rock, unless there is a more
restrictive state/specifying agency specification.
Option A -
If rock is encountered and 9” [225 mm] or less of the full length foundation
tube remains to be embedded.
A. Drill a 12” to 16” [300 to 400 mm] diameter hole into the rock.
B. Drill the hole 3” [75 mm] deeper than the required embedment depth.
C. Fill the hole with MSC.
D. Place the foundation tube and rebar ring per the “Sleeve in a Concrete Footing
(Poured Footing)” section.
Option B -
If rock is encountered and more than 9” [225 mm] of the full length foundation
tube remains to be embedded.
A. Drill a 12” to 16” [300 mm to 400 mm] diameter hole into the rock. The minimum depth
to the bottom of the hole from the ground line shall be 21” [525 mm]. The 21” [525
mm] includes 3” [75 mm] below the tube.
B. Cut off the bottom end of the foundation tube so the top of the tube will be flush with
finished ground.
C. Follow the steps in C and D in “Option A” above.
Foundation Tubes with Soil Plates
For Foundation with Tubes with Soil Plates, remove the soil plate from the sleeve and follow the
“Foundation Tube” steps above.
Driven Posts
For Driven Posts, it is recommended that the post be installed with a Foundation Tube. Follow
the Foundation Tube steps above.
Bottom CRP-Posts 1 to 3
Complete the following steps to place Bottom CRP when encountering rock:
Select Option A or Option B below when encountering rock, unless there is a
more restrictive state/specifying agency specification.
Option A -
If rock is encountered and 30” [750 mm] or less depth is required to
complete the assembly of the full post:
1.
Drill an 18” [450 mm] diameter hole into the rock.
2.
Place the rebar cage and Bottom CRP in the hole. Complete the steps in the “Bottom CRP
with Concrete Footings” section for the assembly of the rebar cage and the Bottom CRP.
Option B -
If rock is encountered and more than 30” [750 mm] is required to complete
the placement of the full rebar cage:
1.
Drill an 18” [450 mm] diameter hole 33” [825 mm] into the rock.
2.
Cut off the rebar cage so there will be 3” [75 mm] of concrete below the cage.
3.
Follow the steps in C and D in “Option A” above.
