Download presentation

Presentation is loading. Please wait.

Published byDarrell Grace Modified about 1 year ago

1
The role of microstructure in the incremental behavior of granular materials V. Magnanimo, N. Kumar and S. Luding MSM - University of Twente (NL)

2
We observe the (often disastrous) MACROSCOPIC behavior and we want to model it …. ….how is this related with the MICROSCOPIC structure?

3
Evolution of microstructure [Behringer (Duke)] Evolution of the microstructure

4
Inhomogeneity & anisotropy, instabilities & structures, rotations [Luding (UT)] Evolution of microstructure

5

6
Material idealization

7
Experimental background

8

9
Yang, Li and Yang (2008) Geotechnique 58(4) Triaxial compression samples prepared with: dry deposition moist tamping

10
ISOTROPIC SYSTEM

11
Numerical protocol

12
Coordination number: HISTORY of the sample Magnanimo et al. (2008) EPL

13
Elastic moduli We apply ( = inf) an incremental strain ij and measure the variation in stress ij after relaxation Calvetti et al. (2003) Rivista Italiana di Geotecnica 3 Magnanimo et al. (2008) EPL Sibille et al. (2009) EJECE 13(2)

14
Amplitude of the increment

15
Elastic moduli dependence on microstructure G/B Magnanimo et al. (2008) EPL

16
Theoretical model with anisotropy

17

18

19

20

21
Luding and Perdahcioglu CIT (2011), Magnanimo and Luding, Granular Matter (2011) Simple constitutive model

22
ANISOTROPIC SYSTEM undrained biaxial test

23
O.I. Imole et al. KONA (2013), Kumar et al. Acta Mechanica (under review) Shear Stress Evolution of stress and fabric Deviatoric fabric dev =√3 J 2 F dev =√3 J 2 Fc definition of fabric

24
We apply purely deviatoric perturbations along the path Elastic moduli

25
Incremental elastic behavior

26
Small enough before any local rearrangement happens How small is small?

27
Bulk modulus

28
Anisotropy modulus

29
Shear modulus

30
Theoretical prediction undrained cyclic biaxial test

31
Incremental elastic behavior

32
F dev =√3 J 2 Fc

33
Luding and Perdahcioglu CIT (2011), Magnanimo and Luding, Granular Matter (2011) Simple constitutive model

34
Initial state: isotropic volume fraction Shear Stress Deviatoric Fabric Undrained biaxial test: calibration

35
Undrained CYCLIC biaxial test: prediction Initial state: isotropic volume fraction Shear Stress Deviatoric Fabric

36
Isobaric compression

37

38

39

40

41
Conclusions We analyzed the incremental behavior of isotropic granular samples and we linked is with the coordination number We analyzed the incremental behavior of anisotropic granular samples and we linked is with volumetric and deviatoric fabric When a simple constitutive model with evolution equation for fabric is introduced and calibrated with the moduli cyclic shear can be predicted

42
Thank you

Similar presentations

© 2016 SlidePlayer.com Inc.

All rights reserved.

Ads by Google