Foundation/Piling Question

[AlvinofDiaspar]

Posting on behalf of victord66:

On most condo projects I’ve looked at in downtown Toronto they usually dig the foundation and put in Soldier Piles with timber lagging. Even before they start to poor the concrete though, the timber lagging seems to get covered with a concrete layer of sorts. What is this? Also on sites I’ve watched from scratch, they always start by drilling deep holes around the perimeter of the project and then immediately pouring concrete in the holes. There are no H piles on site at this point. How then, do these concrete piles relate to the soldier piles? Or would you call these secant pilings? Do they actually use a combination of secant piles and then add soldier piles with lagging?

I know this all sounds rather confused, but as stated I’m not an engineer.

Thanks for any help.

 

[TrickyRicky]

Are you referring to the rigs that drill angled holes into the earth wall? These are tie-backs. A hole is drilled into the earth at an angle. A steel cable is anchored into the hole and a cementitious slurry is injected into the hole. The steel cable is tightened and bears against the side of the excavation wall to help hold or "tie-back" the retaining wall. This is particularly important in excavations right up against an existing building where sideways displacement of the wall must be limited by law.

That is the basics but someone more familiar with the process can add to or correct what I said.

 

[ChesterCopperpot]

AoD - your answer might be in here

https://docs.google.com/viewer?a=v&...qa7Tlq&sig=AHIEtbSpa2yCmdjdBh9YdkAOW1WsYv9pFA

 

[victord66]

AoD - your answer might be in here

https://docs.google.com/viewer?a=v&...qa7Tlq&sig=AHIEtbSpa2yCmdjdBh9YdkAOW1WsYv9pFA

Thank you, this is just what I was looking for.

 

[victord66]

On another issue regarding piles. My apartment overlooks the sites for Chaz, CasaII and One Bloor. For the past few months CasaII has been planting piles around the perimeter of the site but more recently they have started putting them right in the middle of the site. And these are much more substantial, the kind where they construct a large diameter rebar mesh, lower it into the hole and then fill it in with concrete. My question is, if they are going to excavate the site, why put piles right in the centre of the excavation?

 

[ChesterCopperpot]

It's probably the elevator/stair core foundations

 

[victord66]

I don't think it could be elevator foundations. They put those in after they finish excavating. Don't forget, excavation hasn't even begun yet. As I understand it (and I've watched One Bloor from day 1), they plant piles around the perimeter of the site, then they excavate, then they start pouring the concrete foundation. Why would they plant piles right in the centre of this site before excavation has even started? Gotta be a reason.