Acoustic emission at wedge indentation fracture in quasi-brittle materials

Abstract

To improve the safety and automation of mechanical excavation methods used in tunnels, this present report studied the behavior of rock materials indented by a single cutter, based on the theory of indentation fracture mechanics. The development of microcracks during the indentation process and the correlation between microcracks and macrocracks was investigated using the nondestructive technique of acoustic emission. Microseismic activity of the microcracks received by the acoustic emission (AE) technique was used to interpret and represent the initiation and propagation of macrocracks. As the wedge angle increased, the maximum indentation force increased, but the nominal indentation pressure and the destructive indentation depth decreased. On the other hand, the direction of macrocrack propagation did not significantly change with the various wedge angles. Furthermore, the localization occurred earlier and the dimensionless radius of the elasto-plastic interface decreased with increased wedge angle. In addition, the dimensionless radius of the elasto-plastic interface obtained by the experiment was consistent with closed-form analytical solutions.