That’s the kind of projected hypothesis I was looking for the last time we had this topic open. Contingency planners may be working overtime this Christmas/New Years…
I think they may have found the reason for why the thing is leaning in the first place. The existing pilings could be in soft sand and moving. They could add all the pilings they want and it’s still not only gonna move/tilt but it’ll sink as well and may already doing that.
Well the new pilings are planned to go all the way down to bedrock, so the soil in between the surface and bedrock shouldn’t affect them. They don’t depend on friction with the various soils to support the weight of the building. But another problem is that all of the new pilings are around the perimeter of the building rather than underneath it. And the foundation of the building is designed to be supported on a large number of pilings beneath the building rather than just at it’s edge. It’s kind of like a cardboard box full of books that has the bottom just folded over rather than taped. You have to pick it up from the bottom, not just the sides. I’m not convinced that exactly how well the existing piles will support the “bottom of the box” is knowable, so it’s going to be difficult to determine how much stress that the buildings structure was not designed for will exist when the external piles are tied into it. So even if the pilings successfully stop the building from tilting further, it will be important to inspect the foundation regularly for cracks that might indicate the the center of the building was still sinking even if the edge wasn’t. And that will have to continue for the life of the building.
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weren’t there also some people saying the act of driving the new pilings was causing the soil to shift, which might be some reason for the recent increases in lean?
( really cool details in your explanations btw! )
Yes. Think about what happens when you dig a hole in the sand at the beach. Near the surface, you have to worry about sand collapsing into the hole from the sides. But when you get down to where the sand is saturated, it just flows into the hole almost like water. You end up with a watery pool at the bottom of yur hole that is a bigger diameter than the hole above it. From the description, THAT is something like what people think happened when they were drilling the holes for the new piles. Instead of just removing the soil from where they want to put the new pile, the suspicion that in some layers, the soil was flowing into the hole FROM BENEATH THE BUILDING and being removed.
My point is that even if they DO manage to successfully install the new piles down to bedrock, that might not ultimately be enough to render the building safe. And of course this is in an earthquake zone. How much of the safety factor designed in to survive earthquakes has already been used up supporting a building that is tilting? And if they do, in the end, support a proportion of the weight of the building in a way it was not designed for? Add to that the fact that much of the building is supported on soil that is prone to “liquefaction” and is likely to be less solid than usual in an earthquake. Even if they “fix” this, I would not be sufficiently confident that this building could survive an earthquake.
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