We present a rigorous validation of the analytical Amadei solution for the stress concentration aroundudan arbitrarily orientated borehole in general anisotropic elastic media. First, we revisit the theoreticaludframework of the Amadei solution and present analytical insights that show that the solution doesudindeed contain all special cases of symmetry, contrary to previous understanding, provided that theudreduced strain coefficients b11 and b55 are not equal. It is shown from theoretical considerations andudpublished experimental data that the b11 and b55 are not equal for realistic rocks. Second, we develop aud3D finite element elastic model within a hybrid analytical–numerical workflow that circumvents theudneed to rebuild and remesh the model for every borehole and material orientation. Third, we show thatudthe borehole stresses computed from the numerical model and the analytical solution match almostudperfectly for different borehole orientations (vertical, deviated and horizontal) and for several casesudinvolving isotropic, transverse isotropic and orthorhombic symmetries. It is concluded that theudanalytical Amadei solution is valid with no restriction on the borehole orientation or the symmetryudof the elastic anisotropy.
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