Cross-crack group interaction and initiation mechanism under hydraulic-mechanical coupling.

Based on the distributed dislocation function, the complex function of arbitrary position and branch cross-crack group under hydraulic-mechanical in the infinite plate is derived and the maximum Mode I and Mode II stress intensity factors (SIFs) of cross-crack group are obtained. The influence of cross-crack group geometry parameters on the maximum SIFs is analyzed and the multiple cross-cracks dangerous zone is obtained. Using the maximum shear and tensile SIF ratio criterion as a basis, the initiation process of double cross-cracks is predicted and verified by red sandstone double cross-cracks uniaxial compression test. Results show that for the double cross-crack in an infinite plate, h/a should be greater than 8 and the value of α 2 should not range from 75° to 90° to avoid possible cracking. For the triple cross-crack in an infinite plate, when the water pressure is low (less than 5 MPa), the influence of the stress field exceeds the influence of water pressure. For red sandstone samples with double cross-cracks under uniaxial compression, the inner tips of cross-cracks always connected and penetrated and the inner and outer tips of cross-cracks often eventually joined together. The multiple cross-crack initiation criterion was validated by the good agreement between the test results and the prediction results of red sandstone with double cross-cracks. All the initiation mechanisms are Mode I fracture. [ABSTRACT FROM AUTHOR]