A unified method to predict diffuse and localized instabilities in sands

Abstract

A simplified method to analyse diffuse and localized bifurcations of sand under drained and undrained conditions is presented in this paper. This method utilizes results from bifurcation analysis and critical state plasticity theory to detect the onset of pure and dilatant shear band formation, static liquefaction and drained shear failures systematically. To capture the soil collapse observed in experiments, the instability state line concept originated by Chu, Lo and Lee in 1993 is adopted. Emphasis is given to examine how the presence of pore-fluid may facilitate or delay instability after yielding occurs. The predictions of instabilities are compared with experimental data from triaxial compression tests on Toyoura and Changi sands.

Keywords:

• bifurcations
• static liquefaction
• diffuse instability
• shear band
• instability state line

Acknowledgements

The author thanks Dr Dariusz Wanatowski of the University of Nottingham for providing experimental data relating to drained triaxial compression tests on Changi sand. Financial support through a graduate fellowship from Northwestern University is gratefully acknowledged. The expert review from the anonymous reviewer is also gratefully acknowledged.

 Sandia National Laboratories is a multi-program laboratory managed and operated by the Sandia Corporation, a wholly owned subsidiary of the Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.