Finite element analysis of effect of lining on damage in viscoplastic rocks

This paper presents the constitutive aspects and a finite element application for an energetic damage criterion within Cristescu’s viscoplastic constitutive law. The numerical model is implemented in finite element code LCPC-CESAR [1] by the author. The numerical solution is used to perform an analysis of the evolution of the damage zones around a circular lined cavity in a viscoplastic material subjected to a far field stress. Two important factors regarding the opening stability, namely the lining mounting time and the tunnel face influence, are analyzed. The initial stress of rock mass varies with the depth at which the tunnel is excavated and this fact determines a bigger displacement of the tunnel bottom than the tunnel ceiling. The time emphasizes this asymmetry. The results obtained are in completely accordance with the practical observations.