Strain-dependent shear deformation characteristics of grouted rocks and applications to numerical analysis of underground excavations

Abstract

Construction of tunnels in jointed rocks entails rigorous pregrouting works to ensure safe excavation conditions. Grout-filled discontinuities govern the shear deformation characteristics of the pregrouted site. However, the strain-dependent properties of grouted rock still remains elusive and are rarely reflected in the tunnel design or numerical analysis. The aim of this study is to investigate the effects of grouting on the strain-dependent shear stiffness of jointed rock mass. Experimental studies are conducted on intact grout, planar-jointed rock and grouted rock columns using two resonant column apparatus. The effects of grouting are examined for different stress and strain levels. The experimental results are applied to the numerical analysis of tunnel excavations in grouted rock mass for different shear stress and strain levels using FLAC 2D. Emphasis is placed on the importance of small-strain nonlinearity and stress reduction induced by excavation.