Installation Issues of Braced Excavation with Sheet Piles
Installation Issues of Braced Excavation with Sheet Piles
(OP)
I've been informed that the contractor is hitting 6-7" diameter rocks during the installation of the sheet piles for a braced excavation I've designed. They would like to essentially not drive the piles to the required depth.
The braced excavation is roughly 7 feet deep and the piles should be driven to at least 9.5 feet per my design. They want to stop driving piles that encounter these rocks at generally 1.5'-2' short of the designed depth. There are two levels of walers and struts that are to be installed as the excavation progresses.
My question is what is typically done in a scenario such as this? Do I just tell them that it needs to be installed to the required depth and that it's a means-and-methods item? Can they just locally excavate and remove the rocks as they are encountered? I've been told that it isn't just a pile here and there but could be 3-4 piles in a row with this condition.
Thanks for any comments! I don't have much experience with the installation and resulting field issues of these sorts of walls.
The braced excavation is roughly 7 feet deep and the piles should be driven to at least 9.5 feet per my design. They want to stop driving piles that encounter these rocks at generally 1.5'-2' short of the designed depth. There are two levels of walers and struts that are to be installed as the excavation progresses.
My question is what is typically done in a scenario such as this? Do I just tell them that it needs to be installed to the required depth and that it's a means-and-methods item? Can they just locally excavate and remove the rocks as they are encountered? I've been told that it isn't just a pile here and there but could be 3-4 piles in a row with this condition.
Thanks for any comments! I don't have much experience with the installation and resulting field issues of these sorts of walls.





RE: Installation Issues of Braced Excavation with Sheet Piles
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RE: Installation Issues of Braced Excavation with Sheet Piles
RE: Installation Issues of Braced Excavation with Sheet Piles
I'm not sure if moving the bottom level of support with the progressing excavation will be an option with some other complications within the pit (utilities).
Local excavation may be an option. Do you know if it is possible to install the top waler system, continue excavation, then locally excavate to remove obstructions, then continue to drive those piles that were obstructed? I'm concerned with 1) Damage to the waler system while continuing to drive the pile and 2) Buckling of the pile as it is no longer fully supported on both sides by soil while being driven.
RE: Installation Issues of Braced Excavation with Sheet Piles
IMHO, not a wise move. After excavation, the sheeting will be unstable since it has no embedment to keep it from moving inward. The bottom of the sheeting could "kick in" suddenly, without warning - very dangerous. That's why the lower ring is dropped as the excavation proceeds, as PEinc recommended.
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RE: Installation Issues of Braced Excavation with Sheet Piles
www.PeirceEngineering.com