Different Aspects of Modelling Elasticity and Strength of Anisotropic Rocks

Due to the evermore confined building land on the ground and the accompanied need of relocating congested infrastructure facilities to the subsurface, future underground works in urban areas will more frequently have to be carried out in geologies with increased complexity of the materials, including geomaterials with a pronounced anisotropic behaviour.

This statement can also be applied to the plans of developing an intra-european high speed railway system, which will increase train transport in speed and volume considerably. Most of the deep European base-tunnel projects in competent grounds have already been finished, however, to accomplish the plans, it is still required to establish the missing links, in terms of building flat-lying base tunnels in difficult geology.

With increasing ground complexity including anisotropy, also the demands put on constitutive models for the numerical simulation of underground excavation works will grow. A comprehensive constitutive model must account for the complex behavioural mechanisms of these materials to predict realistic values for stresses and displacements. As part of a large current field of research, anisotropy in geomaterials is progressively being investigated and ever more advanced constitutive models are being developed.

This paper provides information on the different sources of anisotropy in intact rocks, as well as in rock masses, and the terms inherent and induced anisotropy are explained. After examining the influence of stress-induced anisotropy on the mechanical behaviour of rocks, an alternative approach within the framework of hyperelasticity for modelling of the elastic range is presented. Finally, contributions with respect to the strength characteristics of anisotropic rocks are made.