Only if the force exceeds the stress intensity, the fracture can extend and lead to a plurality of different Kaiser effect
The purpose of this work was to confirm the existence of acoustic emission (AE) Kaiser effect
(KE)  in Estonian oil shale, and to compare the respective data obtained about working mine pillars (Fig.
Xu, "Evolution and propagation of material defects and Kaiser effect
function," Journal of Seismological Research, vol.
The acoustic emission method only needs to obtain the rock core of the corresponding measuring point, and the Kaiser effect
of the rock can be used to estimate the in situ stress.
However, in the process of cyclic loading and unloading, the AE signal of coal samples shows an obvious Kaiser Effect
For example, Holcomb (1993) and Lavrov (2003) summarized and analyzed the relationship between the Kaiser effect
and rock failure.
Pottery mixture specimens show the Kaiser effect
Thus, the Kaiser effect
in the material is manifested not only in the form of acoustic emission activity burst but also in the form of a sharp change in the spectral characteristics of the AE signals.
is the phenomenon that no AE activity is observed until the load reaches the level of the previous maximum load.
During the second cycle the activity of the ultrasonic emission confirmed the Kaiser effect
. Until the previous value of the acting load had been achieved, only minimum activity of the acoustic emission was observed.
Lavrov  observed the Kaiser effect
in a brittle limestone cyclically loaded with different loading rates and found that damage formed in rock at a high loading rate can hardly be revealed by reloading with slow rate, yet the damage formed during loading with slow rate can be successfully revealed by using fast reloading.
In the figure, these stresses are normalized by the compression strength of the rock tested, [[sigma].sub.b.] The Kaiser effect
of AE is well recognized in the range of the pre-stress below 22 % of the [[sigma].sub.b], giving the underestimation of pre-stress.