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Active and Passive Earth Pressure Coefficients

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Active and Passive Earth Pressure Coefficients

Dipanjan Basu
Should we use peak friction angle or critical state friction angle for Ka and Kp? What is the theoretical basis? What are the practical implications?
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Re: Active and Passive Earth Pressure Coefficients

rsalgado
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This post was updated on .
The reference listed below addresses this point for gravity walls:

D. Loukidis, R. Salgado
"Active pressure on gravity walls supporting purely frictional soils"
Canadian Geotechnical Journal, 2012, Vol. 49, No. 1 : pp. 78-97(doi: 10.1139/t11-087)

To summarize the conclusions of that paper:

1) the active earth pressure coefficient is a function of the wall displacement;
2) the acceptable wall displacement is related to the limit state being considered;
3) at wall crest displacements usually associated with limit states of interest, extensive zones in the soil mass will have reached a critical state.

If one were to take a simple approach, EA should be calculated using the plane-strain friction angle (equal to approximately the triaxial-compression friction angle plus 4 degrees). This recommendation is consistent with discussion in The Engineering of Foundations. A better approach might be to carefully define limit states to be considered and use the figures and equations provided in the above publication for gravity walls, which provide values based on soil state (density and stress level).

This remains a topic requiring research.
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