Abstract: The existing conditions and engineering safety should be considered in the widening of Jinjishan tunnel, due to the complex environment and the numerous control factors. The analysis on the control factors of the widening of Jinjishan tunnel shows that: 1) option 3, in which tube D will be installed and tube A will be widened, may be adopted; 2) tube B and tube C should be reinforced and protected before tube D is constructed; 3) microvibration controlledblast technology should be applied in blasting, and vibration monitoring, traffic control and trolley protection should be implemented for the existing tubes; 4) the loose rocks behind the lining should be cleared as far as possible before balsting is made to dismantle tube A, and prereinforcement and manual primary support chiseling may be executed. 

Key words: Jinjishan tunnel, widening, safety control