A Method Of Elastoplastic Back Analysis By Emulating Construction Of Tunnel

In this paper, a method for elastoplastic back analysis simulating tunneling construction sequences is proposed. The parameters cohesion and friction angle of surrounding rock can be determined thought the proposed back analysis method. A new assessment approach for tunnel stability is also derived.Systemic numerical tests are made first, to study the parameter sensitivity of cohesion and friction angle and other elastic parameters to the convergence in tunnel. Some comprehensive parameter sensitivity laws have been draw thought these numerical tests.The method of emulating back analysis is illustrated secondly, in detail by tracing the excavation and supporting conditions by the special numerical modeling rested in FINAL program.Based on the idea of the measured displacement can be divided into elastic and plastic parts, Elastic parameters can back analyzed by the elastic displacement, which is the measured instant after blasting excavation. The strength parameter can be got by plastic deformation, which is the measured during the period of construction loop without blasting excavation.Lastly, depending on Fenner formula, a new and valid evaluating criterion for tunnel stability is presented and the effect of deformation modulus, cohesion, internal friction angle and overburden can be considered.