Abstract: To reveal the failure mechanism of intermittent jointed rock in deep-buried engineering, true triaxial compression tests of intermittent jointed sandstone with different joint occurrences (dip and strike) were carried out, and acoustic emission (AE) system was used to monitor the failure process of specimens in real-time. The influences of joint occurrence on sandstone failure form, strength, deformation characteristics, AE evolution characteristics, and characteristic stresses were systematically analyzed. The results show that under the condition of true triaxial stress, when the intermittent joint strike is parallel to σ₂, the specimens with joint dip angles of 0°, 30°, and 45° exhibit tensile-shear mixed failure, while the specimens with joint dip angles of 60° and 90° exhibit slipping-shear failure and conjugate shear failure, respectively. When the intermittent joint strike is parallel to σ₃, the failure mode of the samples with different joint angles is “internal shear and external spalling”, indicating that the joint strike has a greater influence on the failure mode of the specimens than the joint dip angles. The strength, crack initiation stress, damage stress, elastic modulus, and peak strain of specimens all decrease first and then increase with the increase of joint dip angle. The strength, initiation stress, damage stress, and peak strain of the specimens with joint strike parallel to σ₂ are lower than those with joint strike parallel to σ₃, and the influence of joint strike on the elastic modulus of specimens is minimal. In addition, the duration of the AE quiet period and the proportion of AE high-frequency signal during this period decrease first and then increase with the increase of joint dip angle. When the intermittent joint strike is parallel to σ₂, the cumulative number of AE hits during the failure process of the specimen decreases first, then increases, and then decreases with the increase of the joint dip angle. When the intermittent joint strike is parallel to σ₃, the cumulative number of AE hits during the failure process of the specimen increases first and then decreases with the increase of the joint dip angle. The research results provide a scientific basis for the failure mechanism analysis of intermittent jointed rock mass and the prevention of engineering geological disasters in deep-buried engineering.

Key words: natural rock mass, intermittent joints, joint occurrence, true triaxial test, failure characteristics