Issue 36

S.R. Wang et alii, Frattura ed Integrità Strutturale, 36 (2016) 182-190; DOI: 10.3221/IGF-ESIS.36.18 185 Figure 3 : The flow chart of recording AE events. Name Density [kg/m 3 ] Bulk modulus [GPa] Shear modulus [GPa] Cohesion [MPa] Friction angle [°] Tension [MPa] Main cells 2650 15 11 2.8 45 0.60 Defective cells 2650 15 11 2.8 45 0.55 Weak cells 2650 15 11 2.8 45 0.14 Table 1 : Physical and mechanical parameters of the model. Loading and Boundary Conditions As shown in Fig. 5, the rock plate was hinged to the both ends with the fixed bearing in the vertical direction and the spring bearing with a stiffness 6.0 × 10 4 N/m respectively in the horizontal direction. The concentrated loading was applied in a circular zone with a diameter of 10 mm in the center of the upper surface of the model. To avoid drastic disturbance of the calculating system, the compressive stress was increased linearly from 0 to a final stress of 12.0 MPa. R ESULTS AE in the Failure Process of the Rock Plate s shown in AE location maps (Fig. 6), the results showed the obvious distribution differences between the initial cracks and the ultimate cracks of the rock plate in the test. And the AE hits-time curve could be divided into four stages in the process of bearing load to instability of the rock plate under the concentrated loading condition (Fig. 7). A