Damage mechanics of jointed rock in tunnelling

Abstract

Abstract. In this chapter, an anisotropic damage model is established in strain space to describe the behavior of jointed rock masses under compression-dominated stress fields. The research work focuses on rate-independent and small-deformation behavior during isothermal processes. It is emphasized that the damage variables should be defined microstructurally rather than phenomenologically for jointed rock masses, 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; 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 behavior of this model. In order to eliminate the complexity and arbitrariness in. the formulation of phenomenological anisotropic model, systematic micromechanical analysis has been done on damage elasticity, damage evolution laws and micromechanics of different types of microdefects.

Damage Micromechanics for Constitutive Relations and Failure of Microcracked Quasi-Brittle Materials

“…Two examples of well-established and extensively applied damage models for ductile solids are the phenomenological Lemaitre and Chaboche's (1988) model and the micromechanics-based Gurson's (1977) model. For microcracked brittle or quasi-brittle materials such as concrete and rocks, some of the much simplified phenomenological models have also been adopted in the analysis of such important engineering structures as dams (Linsbauer et al, 1989;Yang et al, 2003).…”