Stiffness of Sands

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• Dr Sadik Oztoprak
• Friday 14 March 2008, 16:30-17:30
• Engineering Department - LR6.

If you have a question about this talk, please contact Zelda Stuck.

Deformations of sandy soils around geotechnical structures shows that strain level is generally changing from small to medium under static loading. In this strain range the soil exhibits non-linear stress-strain behaviour which should be incorporated in the deformation analysis. To understand and discuss the non-linear elastic sand behaviour, a database was constructed including shear modulus degradation curves of 457 tests in order to produce best-fit functional relationships for shear stiffness of sandy soils. Obtaining a unique S-shaped curve of shear modulus degradation, a modified hyperbolic relationship was fitted. The new curve fitting parameters, elastic threshold strain and characteristic reference strain, were defined for soil type and stress level. With these properties, the proposed hyperbolic relation seems very useful to model the non-linear elasticity of the sands and promising to incorporate into analytical or numerical methods. By this means, the proposed hyperbolic relation incorporated into FLAC3D software to model the pressuremeter tests in sand. Causing less disturbance in the soil and providing initial stress conditions, pressuremeter test is a powerful tool for deformation-based modelling. It is thought that if the observed behaviour in a pressuremeter test can be matched by a finite element program incorporated the proposed non-linear model, then it should be possible to use the same model to predict the behaviour in any full-scale foundations. This presentation will give the promising results of modelling a pressuremeter test which will lead to model some geotechnical foundations in the future.

This talk is part of the Engineering Department Geotechnical Research Seminars series.

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