Abstract：The rock around tunnel is usually loosed by blasting excavation behaviors. The nonlinear plastic properties in the loose area influence greatly the measurements of tunnel deformation. A new back analysis method is proposed based on the simulation of construction sequence step by step. The measured displacement is divided into elastic and plastic parts according to the different tunneling states. A back analysis method for the elastoplastic displacements of broken rock zone around tunnel is proposed based on the measured plastic deformations. An example shows that the proposed back analysis method is reliable and useful for tunnel engineering.
