The West Route of the South to North Water Transfer Project is taken as the engineering background and the excavation disturbed zone in surrounding rock of tunnel by tunnel boring machine (TBM) driving are studied. Considering the rock post-yield damage

a new constitutive model based on the cohesion weakening and frictional strengthening (CWFS) brittle model is proposed and is implanted to FLAC3D program by debugging dll in VC++. Based on the results of triaxial compression tests

this constitutive model is verified through parameter back analyzing by optimization algorithm such as neural network and genetic algorithm. The results show that the model can reflect the elastic characteristic

post-yield characteristic

brittle failure and post-failure residual strength characteristic of slate. Based on this model

the surrounding rock deformation characteristics

stress evolution law and damage characteristic of TBM driving of the South to North Water Transfer Project are studied and also compared with the results by Mohr-Coulomb constitutive model. Finally

the conclusion is drawn that the constitutive model proposed can better reflect the damage rule of the surrounding rock daring TBM driving

i.e. the damage develops along the weak zone.