Failure and acoustic behavior of combinational flaws sandstone subjected to dynamic compression loads

This paper described work initiated with two objectives in mind. First was to explore the influence of strain rate effects on the strength law and deformation characteristics of plate sandstone with combined flaws. Second objective was to analyze the breaking response law and acoustic behavior of flawed sandstone under the influence of disturbance frequency and prefabricated dip angle. Thus, a self-developed physical simulation test system combined with the real-time AE monitoring system, were conducted a series of dynamic cyclic loading tests on the flawed plate sandstone. The results indicated that the dynamic frequencies and dip angles had significant effects on the deformation, strength and failure mode of specimens. Additionally, the degree of specimen failure decreased with the increase of disturbance frequency under the same inclination angle; along with, the most severe failure occurred when the inclination angle was 45 degrees under the same disturbance frequency. The main failure mode of specimens was shear failure from the distribution of AF-RA. Meanwhile, for specimens with small angles (30 degrees, 45 degrees) and low frequencies (0.1, 0.3 Hz), the failure types were more complex (tensile-shear mixed failure). On the other hand, the AE characteristics mainly included three stages: I-initial cycle, II-stable development, and III-damage & failure. The CNT and ENE were greatly influenced by the disturbance frequency and inclination angle. In addition, the b-value decreased and fluctuates violently, and the strength of the samples was reduced as the loading frequency decreased. The specimens with smaller inclination angles had larger internal activity scales and more frequent damage activities with smaller b-value. Furthermore, Correlation dimension Dm was positively correlated with the change of disturbance frequency, and it was smaller when the inclination angle was 45 degrees.