Hydrofracturing Ground Stress Testing in Tunnel Survey in Mountainous Area

The layout of deep buried tunnels and the stability of surrounding rocks are closely related to ground stress conditions. The hydraulic fracturing method is a widely used and mature in-situ stress testing method for deep-buried tunnels. The hydraulic fracturing method was used to test the in-situ ground stress of a tunnel in East China mountainous area, and the maximum and minimum horizontal principal stress and other mechanical parameters were obtained, the characteristics of ground stress were analyzed, which can provide a scientific basis for the layout of tunnel lines and the prediction of rock burst in the surrounding rock. The research showed that the horizontal principal stress of the tunnel increases linearly with the buried depth, and two stress types of thrust stress and strike-slip stress were developed from shallow to deep, respectively. The dominant direction of the maximum horizontal principal stress in the buried depth of the tunnel is consistent with the direction of regional geological tectonic stress, and the angle between the maximum horizontal principal stress and the tunnel strike is less than the optimal angle, which has a certain impact on the stability of surrounding rock. The rock burst risk of surrounding rock increases with the increase of depth, there may be slight rock burst in the surrounding rock at the depth of the tunnel, and relevant measures should be taken to release the ground stress of surrounding rock in time to ensure the construction safety. The research results provide a certain technical reference for the survey, planning, and design of oil and gas pipelines, transportation, and other engineering construction in mountainous areas in the future.