Preconsolidation pressure and bearing capacity 2

[killswitchengage]

Hi
I was wondering, isn't it viable to just limit the bearing capacity to a fraction of the preconsolidation pressure?

 

[GeoEnvGuy]

The deformation will follow the over consolidated slope, is that acceptable or still to much deformation.

 

[Milliontown]

If you are trying to avoid the virgin consolidation curve, I that should work. In this case setting the allowable bearing capacity is not controlled by failure from bearing (i.e. shear failure), but is controlled by serviceability/settlement.

From the USACE Bearing capacity Engineering Manual (pg 8) :
"When practical, vertical pressures applied to supporting foundation soils which are preconsolidated should be kept less than the maximum past pressure (preconsolidation load) applied to the soil. This avoids the higher rate of settlement per unit pressure that occurs on the virgin consolidation settlement portion of the e-log p curve past the preconsolidation pressure. The e-log p curve and preconsolidation pressure are determined by performing laboratory consolidation tests, EM 1110-2-1906"

 

[killswitchengage]

Thank you both
So basically unless your structure is highly sensitive to settlement even in the overconsolidated part then limiting the vertical pressure to a fraction of preconsolidation pressure is enough and no bearing capacity calculations are necessary?

 

[BigH]

killswitchengage - you might want to check out Malcolm Bolton and the use of small strain stiffness for design of foundations and mobilized strength parameter. Here are some links I've found:

https://publications.lib.chalmers.se/records/fulltext/239737/239737.pdf

https://eurocode7.com/todayandtomor...lity - simple calculation models (Bolton).pdf

http://www-civ.eng.cam.ac.uk/geotec...3_soils_and_foundations_vol35_no4_109_114.PDF

https://docplayer.net/184425906-Shallow-foundations-on-clay-malcolm-bolton.html

 

[geotechguy1]

How to determine preconsolidation pressure? A 1D consol test?

The stress conditions in a 1-D consol may actually not be particularly similar to stress conditions under a footing