Abstract: Baotashan tunnel is the longest highway tunnel in Shanxi province with a full length of 10 480 m and a maximum burial depth of 600 m . The complex topography and geomorphology and geological structures give rise to a complicated in-situ stress distribution in the tunnel area. To study the characteristics of rock in-situ stress field in the tunnel area, this paper firstly present the measured results of geostress by hydro-fracturing method, based on which the stress profile along the tunnel is obtained by FEM analysis, and finally the regional tectonic stress field is comprehensively analyzed from perspectives of topography and geomorphology, geologic structure, and geomechanics. The research manifested that in -situ stress in the test area can be defined as middle level stress, and the maximum horizontal principal stress in the tunnel design elevation is mainly concentrated in N42 ° E ～ N56 ° E, and regional tectonic stress field is consistent with in-situ stress field achieved by site test and numerical simulation.

Key words: tunnel engineering ,   stress measurement  ,   finite element analysis  ,   stress field characteristic