Determination of the strength gain of soft soils due to consolidation.

[GeotechPE]

I am evaluating roadway embankments over soft soils C=200 to 700 psf. The maximum embankment height is 86 feet. Using a 2.5:1 slope, the factor of safety is 1.15 < 1.3 = FS required. I do not want to go to a 3:1 slope due to right-of-way issues.

I was going to look at staged construction. The embankment is stable (FS > 1.3) up to a height of about 40 ft. Following consolidation of the foundation soils due to the 30 ft of embankment, the strength of the foundation soils will be higher.

Any methods/references on how to determine the gain in shear strength?

Thanks for your help.

 

[BigH]

Can't believe that you are leaving 5 ft of clayey material in place under a 50 to 85 ft high embankment. Removal of it - in total - and a large toe key seems to be more reasonable; but . . . it is your baby, not ours.