Abstract: As one of the first mines which step into deep mining in China, Dongguashan copper mine uses open stope back-filling mining method with “one partition one” recovery order, therefore mining preparatory tunnel in pillar stope often under high stress. To solve the engineering problem of cracks existing in the reinforced concrete supporting structure of mining preparatory tunnel of Dongguashan pillar stope, combined with practical situation of site tunnel, a structural mechanics analysis model was created. Internal force was analyzed with support structure, and formation reason of crack was found. In the end, some reasonable engineering countermeasures and suggestions are proposed.

Key words: Mining preparatory tunnel, Reinforced concrete sustained and protection, Structural mechanics, Stability