Measurement of the intrinsic process zone in rock using acoustic emission

✍ Scribed by Zietlow, W.K ;Labuz, J.F

• Publisher: Elsevier Science
• Year: 1998
• Tongue: English
• Weight: 688 KB
• Volume: 35
• Category: Article
• ISSN: 0148-9062
• DOI: 10.1016/s0148-9062(97)00323-9

✦ Synopsis

Laboratory specimens with a smooth boundary (no notch) were fabricated from four dierent rock types (grain sizes from 0.1±10 mm) and were tested in three-point bending. The locations of acoustic emission that occurred around peak load were used to characterize the dimensions of the region of localized microcracking, the so-called intrinsic process zone. The size of this zone was found to vary signi®cantly between the rock types, but was not found to vary signi®cantly for dierent size beams of the same material. An approximately linear relation was found between the width of the intrinsic process zone and the logarithm of the grain size. An explanation of size eect evolves naturally by considering the intrinsic process zone as a material characteristic. Two dierent models were used to analyze stress at failure. The ®rst treated the intrinsic process zone as a mathematical crack, an in®nite stress raiser, from which a K IC value was calculated. The second model assumed the intrinsic process zone was a cohesive notch, a ®nite stress raiser, from which the theoretical tensile strength was de®ned. The second method seemed somewhat better at predicting size eect on nominal peak stress.