Soil Plug in Steel Pipe Pile

Question

Soil Plug in Steel Pipe Pile

Sheamus (Structural)

(OP)

22 Apr 22 15:31

A soil plug has developed in a 3 foot diameter pipe while driving into 6 inch minus rock fill. Top of plug is approximately 20 feet from grade; so it could potentially be possible to fill with reinforcement and concrete infill and be well below the the depth of fixity. As long as the PDA results indicate that the axial capacity of the pile is acceptable, then the soil plug will likely remain and concrete in-fill will be placed above. However, if need be, would it be practical/possible to excavate and remove the rockfill inside the steel pipe pile?

JedClampett (Structural) · Answer 1 · 2022-04-22 15:34:52

A little dude (or gal) who's not claustrophobic with a shovel and a bucket.

EireChch (Geotechnical) · Answer 2 · 2022-04-22 16:01:16

Yes you can drill out the plug, depending on the plumbness of the pile. You would get it all out but the majority of it.

Sheamus (Structural) · Answer 3 · 2022-04-22 16:31:39

Use a rock bit slightly less diameter than the ID of the pipe?

PEinc (Geotechnical) · Answer 4 · 2022-04-22 17:33:36

Quote (Sheamus)
However, if need be, would it be practical/possible to excavate and remove the rockfill inside the steel pipe pile?

It all depends on what the design of the pipe pile included. Does the pile design (capacity, deflection) count on the pile being fully concreted, hollow, or soil filled? Does the end bearing capacity depend on just the pile tip steel area or on the area of the pipe steel plus the plugged area inside the pipe pile?

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Sheamus (Structural) · Answer 5 · 2022-04-22 18:08:33

Structural capacity of the steel pipe without any infill (hollow) is adequate. Concrete infill is only required to increase stiffness for deflection. The top of plug is well below the depth of fixity, so the stresses in pipe and deflection is not an issue at this buried location. Pile was designed to be open ended bearing pile on bedrock. However, now that the tip is within overburden rockfill and is now considered a closed ended pile (with a soil plug) the geotechnical axial resistance is likely adequate (pending PDA results). If PDA result is too low, the removal of plug to advance the pile further will have to be considered.

Looking for an economical method and drill bit type to remove plug, if required based on PDA results. Would the contractor have to remove the plug with a rock bit set-up, switch back to the driving hammer to advance the pipe further and possibly switch back to the rock bit if another plug forms? Seems like it could be time consuming and costly. Hopeful that the PDA results are positive, just looking for an alternate solution.

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Soil Plug in Steel Pipe Pile