secant pile wall - shear capacity in concrete "lagging" 1

[mikeCTE]

I am tasked with trying to make a secant pile wall work for a contractor.

The contractor wishes to use 36" diameter piles. The primary piles will be concrete mix with f'c = 1000. The secondary piles will have f'c = 4000 psi with a large W section embedded. Like all contractors, he wants to pinch pennies, so he's trying to push the center to center spacing as large as possible. Due to driving tolerances, this could result in very little overlap between primary and secondary piles.

Everything I have read and researches talks about the primary pile acting as lagging, which I can see. But, I have yet to come across information that specifies how to design it or check its capacity. ACI 318 (2002) has some language in section R22.5.4 talking about shear flow in plain concrete which I think could apply to this situation. However, there seems to be a lot of room for interpretation.

So, I wanted to check with the forum to see if anyone had experience with this and how best to handle it.

Thanks.

 

[slickdeals]

MikeCTE,
Would you mind sharing your calculations for reference?

 

[mikeCTE]

page 1

 

[mikeCTE]

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[mikeCTE]

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[slickdeals]

Thanks for sharing this. Just a nitpick comment, your primary and secondary piles are wrongly labeled.

 

[mikeCTE]

i don't think so.

the primary pile is the one installed first and is typically the one without reinforcing/steel piles. the secondary pile is installed second.

it makes sense when you picture a rebar cage being placed in the shaft. if the rebar cage was installed first, you wouldn't be able to cut the overlapping pile through the cage.

 

[hokie66]

mike,
I agree with slickdeals as to the terminology.

The order of installation is not what makes a pile primary or secondary. Rather, it is their function which determines this, and the reinforced ones are primary.

The piles installed first, using low strength concrete, are generally called 'soft' or 'female' piles.

The piles which are reinforced, either by structural steel or reinforcement bars, are called 'hard' or 'male' piles.

 

[mikeCTE]

http://www.fhwa.dot.gov/engineering/geotech/pubs/gec8/03.cfm

scroll down to figure 3.14.

 

[CELinOttawa]

*cough* I may be able to help here...

In Southern Hemisphere (roughly; Nobody go and get roudy on me!) Hokkie is entirely correct... Primary and Secondary carry their names by FUNCTION.

In the USA and SOME parts of Canada (I do not know Continental & East European practice well enough to comment) the naming is by ORDER of INSTALLATION.

You're both correct. You're also both fine persons, even if one is a man or honour and the other must be satisfied merely with his honor.

 

[mikeCTE]

for the record, i completely agree that the primary pile should be the one with the strength component. in any case...

 

[CELinOttawa]

Ah, and by the way, a quick google search reveals that the USA has both espoused by different groups/engineers/orgs...

I'd certainly vote for naming by function. Just makes more sense.

 

[Ingenuity]

Terminology differences like 2"x4" wood/lumber in the USA compared with 4"x2" timber in Australia.

...then Australia got smart and adopted the metric system so no more 4x2's