STUDY ON EXCAVATION DISTURBED ZONE IN SURROUNDING ROCK OF TUNNEL WITH VARIOUS TBM DRIVING RATES

On the basis of results of the loading and unloading triaxial tests with various unloading rates,Hoek-Brown empirical strength criteria is used to fit slate mechanical parameters including cohesion and friction angle.The numerical simulation method of the TBM driving process is put forward by studying driving characteristics of TBM.The FLAC3D program,which contains loading and unloading criteria,is adopted to analyze the excavation disturbed zone and stability in surrounding rock of tunnel with various TBM driving rates.The results show that when driving rate is greater,the excavation disturbed zone in surrounding rock is smaller,and the surrounding rock is more stable;the deformations of surrounding rock are uniformly distributed after excavation;in the radial direction of tunnel,three zones are obviously shown with displacement and stress variation including strongly varied zone,weakly varied zone and stable zone;along the tunnel radial direction,the maximum principal stress gradually changes from uniaxial to biaxial and triaxial,and the second deviatoric stress invariant forms a closed stress concentration zone which is called "stress dike",which is helpful to rock breaking;the excavation disturbed zone of tunnel varies with TBM driving rates.When the speed increases 100%,the excavation disturbed zone decreases 64%,from 1.1 m to 0.4 m.