Stage settlements

[engrfarhaniqbal]

Good morning everyone.

I am analyzing a mat foundation considering 3 loading stages i.e
1- construction of mat foundation
2- Placement of fill over it.
3- Applying superstructure load over the mat.

I am assuming that after each stage only 10% of the stage settlements would be carried over to ad in the next stage settlements.Please advice me that is my approach right for net settlement to be 10% of stage settlement? In other words you can comprehend it like how much rebound is expected. The strata is granular soils. And the structure to be analysed is 7 storey appartment.

A prompt advice would be much appreciated.
Thank you.

 

[BigH]

I am not sure what you mean by placement of fill over the mat foundation. Wouldn't your superstructure sit on the mat?

In the past I have broken my loads/pressures down to the various stages. As loads are applied, given your granular soils, the soil will "settle" fairly quickly. As it settles, there will be an increase in the deformation modulus for the soil (normally E increases with depth - so each load increase will add a "depth" to the foundation). You can use that "new modulus" for applying the second stage of loading, and so forth. of course, you could detemine the stresses and then the "modulus" value for 50% of the load application and use that new "modulus" value for the whole of the settlement computation.