Jetting Sheet Piles for a Temporary Retaining Structure

[jrl802]

Does anybody have experience in successfully utilizing “jetted” sheet piles as an installation method for sheet piles that were going to be used as part of a temporary retaining structure (TRS)? I have never encountered a need to use jetting for installation and have always been skeptical of using it for earth retention applications.

More background:
The firm I work for did some designs a few years ago for some Temporary Retaining Structures (TRS) consisting of internally braced sheet piles with walers and struts. I worked with a structural engineer colleague of mine on the design. The TRS will be used to maintain an open excavation for construction of an open flume u shaped concrete channel. The owner, a local utility/sewer district has retained our services during construction and the construction contractor is requesting a variance to use jetting to install the sheets even though the specifications clearly prohibit the use. My main concern is that the jetting will erode/disturb the soil such that the soil-structure interaction will be much different than what was assumed for the design thus rendering the TRS potentially unsafe. Am I off-base here?

 

[SlideRuleEra]

I have not come across jetting of sheet piling, and sure would not do it for a cofferdam. Arcelor Mittal has the publication Jetting-Assisted Sheet Pile Driving, but with the procedures described (pipes welded to sheeting, buffer tank in the water supply, vibratory or other hammer in addition to jetting, etc.) can't see much reason for a Contractor to use it or an Engineer to waive a contract requirement on a project like you describe.

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[MTNClimber]

I don't think you're off base. I'm interested as to why they want to jet instead of standard driving techniques. Seems like it would be more of a hassle for the contractor.

 

[cvg]

it may allow deeper installation in stiff clays without refusal in some cases. this would seem to be the only reason to use this technique. so you may run a risk of pile refusal which could also compromise your design, possibly a worse condition than localized soil disturbance caused by the jetting

 

[PEinc]

I'm with SRE, MTN, and cvg on this one. I've rarely seen and done jetting of SSP only to penetrate a very dense layer of granular soils. If not done carefully, or if done excessively, there could be problems. I've seen jetting in stiff clay do nothing more than make small diameter "drill holes" in the clay.

http://www.PeirceEngineering.com

 

[jrl802]

Update:
The contractor is proposing the jetting due to slow production while attempting to drive the sheets through a very dense sand layer that is inter bedded between two softer clay layers. My concern still remains especially since the original design assumed some substantial bending moments at depth.

The contractor is proposing to do a "test section"....more to come....

 

[SlideRuleEra]

...slow production while attempting to drive the sheets through a very dense sand layer...

Is the Contractor using a hammer, in good operating condition, that is sized correctly (energy output) for the job?

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