secant/diaphragm wall

[Egnorant]

I wonder if somebody could guide me to initial sizing of secant pile/wall and diaphragm wall required for a lets say 3-storey basement each with clear height of 4m. Assuming c=o and phi= 35. How can I calculate the reinforcement. Could somebody quote any text book/reference. Most of the books on foundation design talk about soil pressure (simialr to pressures on retaining wall) but I have not found any guidance on structural design. for example I would like to know when is it best to use reinforcement and not the steel section in hard pile. Thanks

 

[dcarr82775]

As to using rolled shapes v reinf piers, it depends on what you need the wall to do and more often contractor's preference. I prefer reinf piers for permanent walls, but some contractors like steel shapes always. Pier spacings are often in the range of 75-85% of the diameter, but the pier size is driven by many different factors: strength, ground conditions, available tooling, site restrictions, etc..

I would find someone who has already designed one to guide you through the process. If you don't know what you are doing you will get eaten alive by the specialty contractor's who do these walls. But if you want to go ahead on your own, design the temporary (construction) conditions using an apparent pressure (braced/tied back). Many text books (I am partial to Peck) give you direction on apparent pressures. Don't forget the water of course.

 

[KootK]

I asked a related question a while back that may be of interest to you: Link.

From the EOR side, I've had to estimate the thickness of these systems in order plan out property line encroachment etc. I've found 750 mm to be a reasonable number. This allows for a 16" steel section, 100 mm of concrete on all sides, and some room for tolerances. You'll want to pay some attention to out of plumb tolerances etc.

In some instances, I've seen the steel piles get removed when all is said and done. In these cases, the local building department has allowed us to encroach upon property lines so long as the concrete left behind is low strength material. Local experience is a good thing to have for this.

The greatest trick that bond stress ever pulled was convincing the world it didn't exist.

 

[Egnorant]

Thanks for the reply. I have found BD42/00 from UK Highways Agency Link, which answers my questions, though I still need to find out a quick way on deciding the initial size (thickness or dia) of these walls. Check this link, I think you will find it useful.

 

[KootK]

That is a good score. Thanks for sharing Egnorant.

The greatest trick that bond stress ever pulled was convincing the world it didn't exist.