Abstract: To quickly and efficiently obtain the insitu stress of the tunnel axis to meet the practical engineering demands, an initial insitu stress interpolation calculation method for a deepburied long tunnel is established based on the geological statistical Kriging method. The crossvalidation iteration is used to calculate each error indicator. The optimal function model is selected from various variogram models for geostress interpolation calculation to obtain the principal stress value and maximum horizontal principal stress direction of the tunnel section. Next, considering the influence of different strata and faults, the principal stress results of the tunnel axis are corrected to obtain the principal stress value and tunnel axis direction. The proposed method, based on a small amount of insitu stress measurement data, is not affected by tunnel survey data and engineering route plan adjustments, resulting in quickly and efficiently obtaining insitu stress value and tunnel axis direction. The engineering application shows that: (1) The calculation value of the proposed method has high fitting accuracy with the measured insitu stress value with a fitting degree of approximately 85% for the maximum horizontal principal stress. (2) The principal stress values of the tunnel axis and the maximum horizontal principal stress direction were obtained through interpolation. The maximum horizontal principal stress of the tunnel was 52.50 MPa, and the principal stress direction of the tunnel was primarily in the NW direction, with local sections in the NE direction.

Key words: deep-buried long tunnel, interpolation of in-situ stress, Kriging interpolation method