The friction angle and critical state void ratio of sands

Author(s): 
Alejo Sfriso
Date: 
Friday, October 9, 2009
First presented: 
17th International Conference on Soil Mechanics and Geotechnical Engineering, Egypt.
Type: 
Published paper
Category: 
Geotechnical

The friction angle of sands is computed by Bolton as the sum of the critical state friction angle and a dilatancy term which is a function of mean effective pressure and void ratio. Critical state is reached when dilatancy vanishes, either due to volume change – in drained shear – or effective pressure change – in undrained shear. Therefore, equating Bolton’s dilatancy term to zero yields, at least theoretically, an implicit relationship between mean pressure and the critical state void ratio of sands. It is found that this relationship yields unrealistic results, mainly because Bolton’s expression if of phenomenological nature and was not intended to be used for this purpose. In this paper, a minor modification to Bolton’s dilatancy term is proposed. It is proved that the modified expression has the capacity to predict both the peak friction angle and the critical state void ratio for any void ratio and effective pressure within the range of engineering interest.

Feature Author

Alejo Oscar Sfriso

Alejo O. Sfriso is a Principal Engineer with 25 years of experience in geotechnical engineering for infrastructure and mining works. He is an expert in the application of numerical methods for geotechnical design and analysis. In addition to his activity at SRK, he is the Director of AOSA - Geotechnical Laboratory, Professor of Soil Mechanics and Geology of the University of Buenos Aires, Vice President for South America of the International Society of Soil Mechanics and Geotechnical Engineering for the period 2017 - 2021, former Professor of Geotechnics at the National University of La Plata and former President of the Argentinean Society of Geotechnical Engineering.

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