A fabric approach for modelling anisotropic behaviour of geomaterials.

Both natural and manmade geomaterials typically have highly anisotropic internal structure associated with lamination plane orientation of rocks as well as particle and interparticle contact of soils etc (Fig. 1). Such fabric anisotropy renders the mechanical behaviour of geomaterials strongly loading direction dependent, which must be properly considered in geotechnical design (Fig. 2).

We have been working on developing a fabric-based approach for modelling the anisotropic behaviour of geomaterials (see my PhD thesis 'Constitutive modeling of anisotropic behavior in geomaterials: the role of fabric'). The heart of this research is the use of a physically based a second-order fabric tensor, an anisotropic parameter defined by the joint invariant with the stress tensor and/or the consideration of fabric evolution law. The fabric tensor employed characterize the physical arrangements of particles, interparticles contacts, the geometric property of the void space and/or orientation of lamination planes in rocks.

This approach has been applied to

  1. model strength anisotropy of geomaterials
  2. model structural effect on behaviour of artifically cemented sand
  3. model strength anisotropy of fibre-reinforced soils
  4. development of a plasticity model for sand accounting for fabric evolution which has been applied to investigate effect of fabric and fabric evolution on strain localization in sand.
  5. model fabric effect on cyclic sand behaviour
  6. model strength anisotropy of sand in direct shear tests
  7. model fabric effect on anisotropic elasticity of sand

sand clay rock

Fig. 1 Anisotropy in geomaterials: sand (left), clay (middle) and rock (righ)

Slope anisotropyfoundation anisotropy

Fig. 2 Variation of loading direction along potential failure planes