Analysis of certain factors affecting the unstable behaviour of saturated loose sand
✍ Scribed by A. Gajo; L. Piffer; F. De Polo
- Publisher
- John Wiley and Sons
- Year
- 2000
- Tongue
- English
- Weight
- 223 KB
- Volume
- 5
- Category
- Article
- ISSN
- 1082-5010
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✦ Synopsis
The factors a!ecting the onset of unstable behaviour in saturated loose sand loaded under drained stress-controlled conditions are not as well known as those involved in its undrained behaviour, which has been analysed in detail.
This paper is intended as a "rst step towards a better understanding of the onset of instability in drained stress-controlled tests and reports on the analysis of certain factors a!ecting the unstable behaviour of saturated loose sand samples subjected to drained stress-controlled triaxial compression tests. The samples are loaded continuously at a constant loading rate and the results are compared with those obtained by other authors who discontinuously applied a load using "nite increments.
A special experimental apparatus was designed so that the axial load could be applied in various proportions by a dead weight and by a pneumatic cylinder in a triaxial cell with no friction on the loading ram.
The paper focuses "rst on the in#uence of the load application method (i.e. by dead weights and by a pneumatic cylinder), which proves important, since the sample always collapses at a more or less constantly low mobilized friction angle when loaded with dead loads, whereas it may have unstable strain jumps starting from a high value of the mobilised friction angle, but may even be stable up to the steady state of deformation, when the axial load is applied by a pneumatic cylinder.
Then the in#uence of the loading rate and loading path is examined and found to be negligible, at least in a "rst approximation. On the other hand, the e!ects of preshear and initial density are shown to have a major role in the onset of collapse: both the preshear and the increase in density lead to an increase in the resistance of the loose sand to collapse under drained stress-controlled conditions.