Caisson Wall

[AAAprince]

I am reviewing a caisson wall that is typical for shoring purpose (king caisson alternate with filler caisson).

Does anyone know the theory of how the filler caisson inter-lock with the king caisson? or how the caissons can act as a wall?

It would be great if anyone could provide me some references.

Thanks!

 

[Zambo]

Is this a secant pile wall?

http://www.deepexcavation.com/secant_pile_walls.htm

 

[AAAprince]

Yes it's a secant pile wall.

I wonder if there is any guideline to determine the overlaps between piles. Any calculations involved?

Also, is there any other consideration when designing this wall?

 

[csd72]

For future reference, be careful about the use of caisson - it means very different things in different regions.

I dont think there is any hard and fast rules on this, it just needs to have sufficient interlock. the intermediate piles work mostly by arching action.

 

[BigH]

http://cedb.asce.org/cgi/

http://WWWdisplay.cgi?169146

(if you can get a copy)
look at:

http://www.secantpile.com

 

[Zambo]

I've worked on bored piles and diaphragm walls but never a secant pile wall. But an interesting subject.

My understanding is that there are primary bored piles constructed first and then the intermediate (secondary) piles are constructed.

The primary piles are spaced at less than the pile diameter so that secondary piles are bored through the concrete cover of the primary piles. So in the case of 4' cover the overlap could be say 3'.

Of course the pile wall will then need horizontal support as excavation commences. This support can be similar to a diaphragm wall and could be steel struts, soil anchors or "top down" construction using the permanent floor slabs as work progresses downwards.

Joints in diaphragm walls can be a problem even though these are proprietry joints lowered into the excavation before casting. For a secant pile wall I can imagine joints could be an even bigger problem as they just rely on the integrity of the concrete at the intersection of the piles.

 

[AAAprince]

Thanks for the input!

Is there any guidelines or code available for the secant pile wall design? Especially a guideline on how to determine the interlock width between piles. I have to show that the wall is workable.

 

[dcarr82775]

I have designed a few secant walls, but never found a suitable design guide. My designs typically use unreinforced drilled shafts for the initial piers, and reinforced structural shafts for the 2nd set of piers. 36" piers at 30" o.c. for example.

I design the structural piers assuming the unreinforced piers support no load. The soil will arch between the structural piers so there isn't a great deal of load on the unreinforced piers. you need to look at the specifications for vertical tolerances to make sure you will always have an overlap given the length of the piers. If the driller needs to use casing you get more overlap than you counted on because the piers end up being larger diameter than specified.