Consolidation settlement

[nagatalluri]

Hi all:

Can anybody suggest me how we consider the influence of a foundation load on soil profile. I mean if we have a footing depth at 8ft. and we have varying lean clays upto a depth of 100 ft, consolidation settlement up to which depth is significant for our calculations ?

Is it the depth where load intensity is 10% of the actual ??

Please suggest.

Thanks
NT

 

[oldestguy]

NT as I referenced in your other post, once you start playing with this method of Hough's using a spread sheet, you calculate the settlement for each foot thick layer as deep as you wish. Then looking at the computed settlements you can judge if 10 % is a reasonable depth to stop computations, etc. As I do it, I make a simple load spread calculation at various depths, rather than any fancy derailed method such as Bousssinesq. After all starting with N values you already are into a rough area as to precision.

The nice thing about using the spreadsheet you can try various situations such as unload an area, as with a basement excavation to see it's effect on how the footing behaves. Also you can pre-load as with a surcharge and see how little footing pressures affect sub soils as a result. A tricky one is for the situation with a footing at the edge of a basement area. That may take a more elaborate way to find existing as well as added pressures down there. Sometimes we need to "estimate' between two extremes.