Open AccessPrincipal stress rotation as cause of cyclic mobility
Author(s) -
JefferiesMichael,
ShuttleDawn,
BeenKen
Publication year - 2015
Publication title -
geotechnical research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.652
H-Index - 10
ISSN - 2052-6156
DOI - 10.1680/jgere.15.00002
Subject(s) - yield surface , geotechnical engineering , stress path , constitutive equation , rotation (mathematics) , triaxial shear test , shear stress , simple shear , principal (computer security) , geology , shear (geology) , mathematics , structural engineering , engineering , geometry , mechanics , computer science , physics , finite element method , petrology , operating system
Principal stress rotation (PSR) has been known to act as ‘loading’ on soils since the seminal work of Arthur et al. some 30 years ago, using the directional shear cell. However, the key insight – reflected in the titles of the original papers – that soils yield under constant stress invariants if the principal stresses rotate, has been consistently neglected in virtually all constitutive models of soil as well as in all procedures/methods of geotechnical engineering practice. This neglect is a pity, as a rather simple softening (annealing) of yield surface size, proportional to the rotation of principal stress, captures much of soil behaviour that is measured in the cyclic simple shear test – an idealisation demonstrated in this paper using a minimal extension of the generalised critical state model NorSand (although the idealised effect of PSR could be implemented in any comparable model as the ideas are general). The extended model captures much of the behaviour encountered in the large body of test data on Fraser River sand. Equally, the implementation of PSR annealing makes clear that there is a further loading process for soil: it is suggested that the rotation of the strain increment direction is the missing additional factor. The model is provided as a downloadable, open-source code Excel/VBA program as a supplement to this paper.