Time-dependent rock—Shotcrete interaction a numerical shortcut

Abstract Shotcrete is an essential support element for tunnels driven according to the principles of the New Austrian Tunnelling Method (NATM). Therefore the state of stresses and strains prevailing in the shotcrete lining is a major factor for assessing the stability of the opening. The rock-shotcrete interaction near the tunnel face is governed by the non-linear time-dependent material behaviour of shotcrete and the time-dependent excavation process. For a realistic assessment of this problem, large-scale calculations based on the Finite Element Method (FEM) are carried out. The calculation models are 3-dimensional and the time dependence is taken account of by a time stepping procedure. This approach implies extensive CPU time even on large-scale computer systems. The present paper is an attempt to analyze the influence of the essential parameters on the rock-shotcrete interaction at an early age of the shotcrete and to derive a hypothetical modulus of elasticity of the shotcrete lining, which allows an approximative but realistic assessment of the real 3-dimensional rock-shotcrete interaction by means of a 2-dimensional FE-Model without an extensive time-stepping procedure.