Investigation on Acoustic Emission Kaiser Effect and Frequency Spectrum Characteristics of Rock Joints Subjected to Multilevel Cyclic Shear Loads

Table 4

Percentage of AE signals of low, medium, and high frequencies in the rock shearing process under four normal stresses.

Normal stress σn/MPa	Low freq./number	Medium freq./number	High freq./number	Total signal/number	Low freq. signal/% (0~35 kHz)	Medium freq. signal/%(35~122 kHz)	High freq. signal/%(122~300 kHz)
MPa	272	8705	563	9540	2.85%	91.25%	5.90%
MPa	224	5734	305	6263	3.58%	91.55%	4.87%
MPa	149	6758	299	7206	2.07%	93.78%	4.15%
MPa	59	3783	80	3922	1.50%	96.46%	2.04%