Settlement in sand given CPT 1

[Civil_TX]

How do you determine the settlement of a spread footing in sandy soil when a CPT is provided with only the Cone resistance and Sleeve friction. Given also is depth, load, and time for creep (yr).

 

[oldestguy]

If you have a relation between Cone resistance and split spoon blow counts, this chart has been found to be valid for sands above the water table. For sands below the water table it is too conservative. Comes from the text by B.K. Hough, "Basic Soil Engineering". The term Bearing Capacity Index is equal to 1+e/Cc

I should have said, this table assumes settlement at 1".

I'll dig around in my stuff. I think I also haveHough's method for calculating settlement in sands from N values.

 

[oldestguy]

In Hough's first edition text "Basis Soils Engineering", in Chapter 12, he presents a chart relating void ratio to compressive stress, showing several examples of in place void ratio varying with log of compressive stress as straight lines. So what this requires is knowing the void ratio to start. He also has a chart showing N value vs Relative Density and then how to get to void ratio.
I believe his text is for sale on the Internet. Original copyright 1957. Again relate that N value to the cone results.

 

[oldestguy]

try a search for the N versus cone.
Here is one link that has some scoop.

https://www.researchgate.net/post/What_is_the_relationship_between_SPT-N_value_and_DCPT-N_value

 

[Civil_TX]

Thank you for the information oldestguy, I was not provided the number of blows (N) is this required to determine settlement? I've found Schmertmann method to be helpful to an extent.

 

[geomane]

There are many correlations available to find the Elastic Modulus from the CPT. Once you find the Elastic Modulus of the different soil layers in your soil profile, distribute the applied stress from the spread footing with depth and calculate the settlement of each layer. Just Google it and do a little research and you will find what you are looking for.