How to analyse a raft foundation

[As-Lag]

Hello

I want to check the strength and serviceability of a concrete raft foundation. The raft is bascically a reinforced concrete ring-beam supporting a reinforced concrete slab.

Given the ground supporting the raft may move due to tree-roots, how should I apply my loading onto the ground? For example; if I assume the ground beneath one corner of the raft sinks or rises, I assume I would check the edge beam for cantilever action. Similarly, the ground beneath the centre of the long beam shrinks so I check the beam for sagging. Are there any rules, standards or examples to guide me?

Any help appreciated.

 

[oengineer]

If you are concerned about tree roots, I am assuming that this is an existing foundation that you are trying to analyze? I say this because I would think vegetation would be stripped for a new proposed foundation.

Here is some info on slab-on-grade foundations:

https://files.engineering.com/getfi...file=Design_of_Slab-on-Ground_Foundations.pdf

Here is another document that might be helpful:

https://files.engineering.com/getfi...._Foundation_Analysis_and_Design_Examples.pdf

I would like at the soil report and determine the allowable soil bearing pressure for the foundation and verify that the foundation works for that. Also, be sure to determine the proper site perpetration for the project/foundation (i.e. type of select fill).

Also, here are some links to a similar posts to what you are asking:

https://www.eng-tips.com/viewthread.cfm?qid=421204

&

https://www.eng-tips.com/viewthread.cfm?qid=426084

 

[As-Lag]

Thank you for your time and effort.

The raft is existing.