Ko At Rest Factor

[SteynvW]

Good Day

Something interesting came across my desk today, the geotechnical report of an existing building has a Ko factor (long term) of 1,2 for at-rest lateral soil pressure.
Is this not supposed to be a maximum of 1?

The site is underlain by clay, can the Ko factor be larger than 1 due to the swell of the clay?

 

[HTURKAK]

Ko factor can be larger than 1.0 in case of overconsolidated clay.

The following para. copy and paste from Foundation Analysis and Design ( by Joseph E.Bowles)

(The upper limit of KoOCR appears to be the passive earth pressure coefficient Kp , and a number of values reported in the literature range from 1.5 to 1.7. It would appear that the upper limit of any normally consolidated soil would be KOjnc < 1.0 since a fluid such as water has K0 = 1.0 and no normally consolidated soil would have a value this large.

The suggested formula
KoOCR = Ko,nc X OCR^n

Ko could be in the range of 0.7 for normal consolidated clay but KoOCR could be larger than 1.0 depending upon the term OCR (overconsolidation ratio) and ..










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