Embedded retaining wall on sloping ground 2

[killswitchengage]

Hi
We have a task to design an embedded retaining solution for 3 underground floors in an urbain environment . The ground is however sloped at 19 degree angle. As shown in the figure attached, the excavated upper part will be about 40 ft and the length of the excavation is about 118 ft.
Geotechnical investigations are under way but it's fairly certain there is no groundwater table in the region and the soil is mostly hard Marly sands, in this situation of sloping ground what are the possible solution baring in mind at the entrance level only 3-4 ft will be excavated?

 

[PEinc]

What does the structural engineer say about this? Can the SE design the building for this great unbalanced lateral earth load? If not, you will need some type of permanent, anchored wall - either a tiedback wall or a soil nailed wall. If an anchored wall, you may need a permanent underground easement. An easement will be difficult to get if the anchors cross over a property line or extend beneath a utility easement. If the SE can design the building to take the lateral load through use of floor slabs, shear walls or a really high conventional, possibly counterfort, retaining wall; you will still need serious temporary excavation support and probably temporary tieback or soil nail easements.

http://www.PeirceEngineering.com

 

[EireChch]

PEinc has nailed it

 

[killswitchengage]

when you mentioned the idea about counter forts against the outer walls I was like: Picasso, I like this.

It's a brilliant idea even if it will take up some space inside the floors.
That being said, because of the sloped terrain, I don't think it will be possible to transfer the loads through the floor slabs unless, they too transfer the loads to piles, meaning you will probably get thick column sections connected to piles.

One can also design the shear walls at the perimeter of the building to transfer loads to pile foundations.
I want to know if it's possible under pseudo finite element method to modify the stress state distribution in the initial state before excavation takes place (sloped ground)

 

[PEinc]

I don't see too many any 40 feet high, conventional, concrete, gravity walls built into a hillside. I suggest that you talk to a specialty geo-structural contractor for ideas and guidance.

The attached PDF is an oldie but it is still applicable for buildings subject to unbalanced earth loading.

http://www.PeirceEngineering.com

 

[Celt83]

PEinc doesn't look like your PDF made it into your last post, would be interested to see the content of that one if you are able to post it.

 

[killswitchengage]

could you please re-upload your file?
Also I wanna know if there is a need for a coupled soil structure analysis in this project

 

[PEinc]

Third try uploading the PDF. Success!

Killswitchengage, sorry but I have no idea what you are asking about the analysis (a coupled soil structure analysis?).

www.PeirceEngineering.com

 

[Celt83]

Thank you PEinc, some good information in there.

 

[PEinc]

Similar information is in some of the FHWA design manuals for anchored walls.

http://www.PeirceEngineering.com

 

[killswitchengage]

I meant soil structure interaction analysis meaning modeling the entire structure and its foundations with the soil, or transferring the structure stiffness matrix to a FE soil software

 

[PEinc]

In my area we have relatively good ground conditions. I have successfully done jobs like this and never used FE analysis. Using FE analysis would be a good idea if you suspect problem ground conditions like poor soils or global instability. However, I recommend using getting and using reasonably accurate soil properties and strata elevations otherwise you may model a problem that doesn't really exist. GIGO!

http://www.PeirceEngineering.com

 

[killswitchengage]

PEinc hank you my man, your PDF was quiet interesting