Lowering a leaning mat foundation
Lowering a leaning mat foundation
(OP)
I've got a client who has a mat foundation supporting a 1,000 kip (fully loaded) silo that is leaning 10". The mat has rotated to produce the leaning silo. The client cannot raise the low end up and wants to investigate lowering the high side.
I don't think this is a safe route to take, but I thought I'd throw the scenario on this forum to see if anyone has any thoughts or suggestions. I've only seen pictures of the area and wanted to get some other opinions before I make a site visit.
I don't think this is a safe route to take, but I thought I'd throw the scenario on this forum to see if anyone has any thoughts or suggestions. I've only seen pictures of the area and wanted to get some other opinions before I make a site visit.





RE: Lowering a leaning mat foundation
RE: Lowering a leaning mat foundation
At best I would say this seems easy but would be highly technical to accomplish without causing the silo to tilt the other way. To be safe it would likely be a lengthy process of drilling some holes, letting them collapse, then start again. The big technical questions are how many, how deep, what angle, and what diameter of hole should be used. Also, with the potential liability, who will do the work?
This is a rather peculiar request, I would start with a local geotech and also talk to a reputable professor in geotechnical engineering.
Would it not be possible to empty the silo then raise and support using a deep foundation system?
RE: Lowering a leaning mat foundation
RE: Lowering a leaning mat foundation
My concern exactly about causing the silo to tilt the other way.
The client actually has a contractor that suggested using high pressure water jetting to slowly remove layers of soil and allow the high side to settle. My concern with this was the water used would saturate the soil and cause too much settlement and the movement of the foundation would be uncontrollable.
I had forgot about the stabilization of the leaning tower of pisa. I'll have to research that a little.
Due to other ancillary equipment and structures on this foundation, the client cannot raise the low side.
RE: Lowering a leaning mat foundation
You have information on the soils? You would need that to determine whether it's differential settlement or the beginning of a bearing failure.
Jetting sounds pretty risky. I would be more inclined to try augers, plus disclaimers writ large.
RE: Lowering a leaning mat foundation
RE: Lowering a leaning mat foundation
First stabilize existing foundation. Piles or compaction grouting.
Underpin and support on adjustable piles or jacks then lower to desired level and leave on temp supports.
Grout underneath.
Jetting alone will give you a base that is saturated and no guarantee against settlement to the correct position or future movement due to bad existing foundation material.
Intrusion Prepakt /marineconcrete.com
RE: Lowering a leaning mat foundation
RE: Lowering a leaning mat foundation
I'd bet some trench or other looseness nearby was at fault.
Jetting is for fools, Never do it.
RE: Lowering a leaning mat foundation
RE: Lowering a leaning mat foundation
They saved the first elevator by jacking it back in place, so you may be able to gleen some good info. from that failure report.