Abstract: In order to solve the problem concerning the wall rock support time in complex geological environment, a series of theoretical and numerical analysis were made on a large span cavity at 1165m level in Jinchun No.3 Mine.First, based on site survey, preliminary engineering geological evaluation on the wall rock was made and it was concluded that the wall rock was in unstable status.Then, theoretical study was carried out on the rheology of Jinchuan rock mass and a nonlinear rheological model was established.The best secondary support time was found by fitting.Finally, in light of the rock mass deformation characteristics, a concept of “support after proper stress release” was proposed, and study was mad on cavity support by numerical calculation method, resulting in a series of conclusions.The research results indicate that support after proper stress release will facilitate the improvement of the self-carrying capability of wall rock mass and consequently, the long term stability of the support engineering.

Key words: Jinchuan rock mass, Support time, Rheology, Numerical analysis, Stress release