Ratio of internal to external deformation of surrounding rocks and a new kind of classification for tunnel surrounding rocks

Based on a great deal of in-situ measured deformation data in tunnel surrounding rocks and the results of numerical simulation, the authors have studied some laws of surrounding rock deformation for two kinds fo soft rock tunnels,then advanced a new concept-ratio of internal to external deformation of surrounding rock which indicates intrinsically the state of deformation of surrounding rock.with the deformation magnitude of the tunnel surface and the value of ratio of surrounding rock, the authors have put forwrd a new kind of classification for tunnel surrounding rocks which is believed to be better that existing classification used for selecting bolting support.