Missing Pile for the Pile Cap
Missing Pile for the Pile Cap
(OP)
Good Afternoon!
The Fly Ash silo is reinforced concrete. It is supported by pile cap and driven piles. However, during the driving of the piles, one was not driven. Basing from actual site conditions, they cannot drive the missing pile. Can anyone suggest a remedial measure for this?
Thank you
The Fly Ash silo is reinforced concrete. It is supported by pile cap and driven piles. However, during the driving of the piles, one was not driven. Basing from actual site conditions, they cannot drive the missing pile. Can anyone suggest a remedial measure for this?
Thank you






RE: Missing Pile for the Pile Cap
RE: Missing Pile for the Pile Cap
The only other option would be to ask the geotech if the overloaded piles are acceptable in their current state. If the overload is small the geotech may find this acceptable.
RE: Missing Pile for the Pile Cap
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RE: Missing Pile for the Pile Cap
I have checked the capacity of the piles, and those piles near the missing pile fails. If I will only check for axial capacity then I would not have any problem with this.
I have tried tying up the three piles near the missing pile. I linked the piles by means of a tie beam within the pile cap to create a frame action and thus, reducing the moment transferred to piles. But still, the piles cannot sustain the load.
RE: Missing Pile for the Pile Cap
First thing, take a look at the fly ash load assumptions. Are they so conservative that the true loading may actually be lower than assumed. For example, does the fly ash unit weight assume fluidizing air is operating in the silo or is the fly ash tightly packed? Is the silo assumed to be 100% filled, or does the maximum fly ash level allow empty space for fly ash volume expansion when fluidizing air is operating?
I'll think about this problem overnight and get back with you tomorrow.
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RE: Missing Pile for the Pile Cap
Fill a path wide enough, around and over the existing piles, to get a crane and leads into position to drive the missing pile. Compact the fill as best you can and put mats on the fill to run the crane on. Then excavate the fill when you are done driving the pile. Since you can make the gravity load work without that pile, leave a void in the pile cap/mat for that pile. Pour the pile cap, with the void. Then bring the crane in on the pile cap, drive that pile, and with some attention to the void detail and rebar fill the void with conc. to pick up the lateral loads. Maybe adjust the thickness and shape of the pile cap/mat in this region also.
RE: Missing Pile for the Pile Cap
Alt: Increase the floor strength (from wall to wall) to allow the load to be "bridged" across the missing pile?
RE: Missing Pile for the Pile Cap
RE: Missing Pile for the Pile Cap
RE: Missing Pile for the Pile Cap
Pile caps for this type heavily loaded structure are designed for minimal deflection (made thick, to increase the cap's moment of inertia). The benefit is that the pile cap strength (section modulus) is much more than theoretically needed. Minimal deflection is important. The loads are so heavy and concentrated that an adequate number of piling will not "fit" directly under the load. The piling have to be properly spaced to perform as intended. Many piling will be some distance from the load. By controlling deflection, the piling that are away from the applied load still contribute almost all of their load carrying capacity and the piling directly under the applied load are not overloaded.
This pile cap (as designed, without modification) should easily bridge the missed pile location and distribute the excess load more or less equally on nearby pile.
You did not mention the fly ash load assumptions, but a fly ash silo in never intended to operate completely filled. If it is totally full (been there, done that) removing the fly ash is an out-of-the-ordinary task. Chances are this silo will never see the maximum load it was likely designed for.
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RE: Missing Pile for the Pile Cap
RE: Missing Pile for the Pile Cap
PMR06 - yes, it is open. Thinking of the cost implication of your proposal and its corresponding adjustment to the project schedule, i it also out of the question. But if its only the solution, then we will let the project manager explore this.
SlideRuleEra - I will try to fill up and reinforce the center and as PMR06 said, maybe it can help redistribute load from the missing pile to the other piles.
Anyway, for the load assumptions, the packing density is 12 kN/m3. The calculated top of stored materials is 13.7m.
RE: Missing Pile for the Pile Cap
RE: Missing Pile for the Pile Cap
I have modeled the pile cap in SAFE. From the pile cap, i put in 101 fixed supports as the pile head. The reactions from the result will be then transferred to the pile. Based the SAFE report, is the moment transferred directly to the pile or the pile cap first?
RE: Missing Pile for the Pile Cap
If you proceed with foundation structural additions to compensate for the missing pile, but do not drive additional piling, won't you be adding dead load to the remaining piling?
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