An energy-based damage model of geomaterials - I. Formulation and numerical results

In this paper, an anisotropic damage model is established in strain space to describe the behaviour of geomaterials under compression-dominated stress fields. The research work focuses on rate-independent and small-deformation behaviour during isothermal processes; It is emphasized that the damage variables should be defined microstructurally rather than phenomenologically for geomaterials, and a second-order "fabric tensor" is chosen as the damage variable. Starting from it, a one-parameter damage-dependent elasticity tensor is deduced based on tensorial algebra and thermodynamic requirements; a fourth-order damage characteristic tensor, which determines anisotropic damaging, is deduced within the-framework of Rice's (1971) "normality structure" in Part II of this paper. An equivalent state is developed to-exclude the macroscopic stress/strain explicitly from the relevant constitutive equations. Finally, some numerical results are worked out to illustrate the mechanical behaviour of this model. (C) 1998 Elsevier Science Ltd. All rights reserved.