An analytical solution for recovering the complete in-situ stress tensor from Flat Jack tests

•A complete analytical solution is derived for obtaining the six components of the far field in-situ stress tensor.•No assumptions need to be made with respect to the orientation of the initial far field stresses.•The slots do not have to be perpendicular to the tunnel axis.•The proposed analytical solution is not sensitive to Poisson's ratio for the rock mass near the tunnel.