Abstract:Integrative action from folding,faulting and squeezing of weaken rocks constitutes great challenge to normal function of tunneling boring machine (TBM). As a case study,the Shanggongshan tunnel for water transfer with a diameter over 3 m,located at the eastern blank of the Puduhe fold,southwestern China,was encountered squeezing,TBM jamming and plastic deforming of shields. Between chainages 4 km+340 m–439 m at a depth of about 200 m,where the sandy and argillaceous slates play dominant roles,together with a gentle dipping of reversed fault,a TBM is seriously jammed several times. Extra-excavation in both sides made the back shield seriously plastically deformed. This paper presents the analysis of its complicated geological background from mineral contents to mechanical properties,together with compression state of the shield from binary to uniaxial as progressive trial excavating for release of the shield. The squeezing of rocks and shield failure occurred more severely in the upper and right part of the tunnel cross-section. Actual measures as manual excavation outside of the shield,steel frame supporting and advanced adit for prediction were adopted. Adjustment of the tunnel alignment was carried out after this section encountered of more faults ahead of the working face. Previous unsuccessful case examples have made us carefully consider the suitability of TBM in complicated geological conditions.