Does the subgrade modulus reaction Ks value differentiate between Raft and Raft-on-piles??? 1

[MikeGeoUSA]

Hi Guys,
I got a soil report where the geotechnical engineer stated that Ks under raft is the same under raft with piles.
Please advise if this possible?

 

[HTURKAK]

I assume,

- If raft foundation without piles is chosen, the analysis (winkler model) can be performed with subgrade modulus Ks.

- If raft foundation with piles is chosen , the same Ks can be used which i disagree for displacement type piles.That is, in case of driven piles ( precast, steel pipe with end cap etc .) the foundation soil will be compacted with lateral pressure exerted by driven piles. In case of bored piles , yes.. Ks would not change substantially.

 

[EireChch]

I dont agree that Ks would be the same under a raft and under a piled raft.

Ks is a function of settlement. A piled raft should have less settlement so therefore Ks will be higher.

 

[ATSE]

Mike - you need a new geotechnical engineer. Of course Ks changes with piles (vs without piles).
Keep in mind that your ks will change across your mat foundation both for piled raft and mat-slab.

 

[dik]

I'm not sure, but I would treat them as two different types of foundations.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[Settingsun]

Perhaps the intention is to add the pile stiffness to the stiffness of the slab?

 

[fattdad]

there is no subgrade modulus for a pile supported slab.

f-d

ípapß gordo ainÆt no madre flaca!

 

[dik]

thanks f-d... didn't know that.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[EireChch]

If its a piled raft, which takes some contribution from the soil, then there is both ks and pile spring stiffness.

Essentially they are just springs...

 

[HTURKAK]

The foundation could be partially supported by soil and piles together. In this case, modelling the raft with FEM and the piles with hard springs and the soil with soft springs is the practice in our region..

Just for sharing the knowledge, i added the section of ( forum building complex Frankfurt ) Notice that, the raft is designed as single structure..

 

[dik]

Take a gander at Millenium Tower in San Francisco...

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik