Comparison of stresses obtained from Acoustic Emission and Compact Conical-Ended Borehole Overcoring techniques and an evaluation of the Kaiser Effect level

Abstract

The purpose of the study was to compare stress values obtained from Acoustic Emission and Compact Conical-Ended Borehole Overcoring stress measurement techniques applied at an underground limestone mine in Japan, and to investigate the effect of rock anisotropy and confining pressure on the Kaiser Effect level which has been used to determine in situ stresses by the Acoustic Emission technique. Initially, Acoustic Emission tests were carried out on limestone cores extracted from horizontal boreholes in a pillar and hanging wall in the underground mine. The stress values obtained were two or three times greater than those obtained by the Compact Conical-Ended Borehole Overcoring method. In the second stage, the anisotropy of a granite block was determined by P-wave measurements. Core specimens extracted from two different directions were pre-loaded under axisymetric triaxial conditions by applying a series of differential stresses. The cores were then re-loaded under uniaxial conditions and the Kaiser Effect levels were determined. It was concluded that both the anisotropy and confining pressure have an important influence on the Kaiser Effect level.

Relation between the shear stress distribution and the resulting acoustic emission variation in concrete beams

“…In addition, the distributions of the AE energy intensity and the signal strength intensity did not demonstrate similar correlations in this study. These conclusions were consistent with findings in previous work Although similar correlations were observed in concrete beams failed in the flexural and the shear mode, the correlation relevant to the shear stresses remained valid in the working stage and the failure stage, whereas the one related to the flexural mode was observed only in the failure phase. …”

“…For instance, the peak stress at the end of the stage was only 81.29% of the concrete compressive strength. These not very great stress levels imply the resulting damage would not be severe; therefore, there was limited accompanying AEs yielded, which then exerted few impacts on the correlation between the shear stress distribution and that of the corresponding emissions.…”

“…Fu et al investigated the measurement of the pre‐existing tensile stress in marble using the Kaiser effect method. Tuncay and Obara compared stress values given by the Kaiser effect‐based method and other approaches and found that the method may sometimes yield two or three times larger estimates. Note that most Kaiser effect‐based techniques are mainly for estimating the maximum stress level that a sample experienced in the past rather than a real‐time stress magnitude.…”

On the Kaiser Effect of Rock under Cyclic Loading and Unloading Conditions: Insights from Acoustic Emission Monitoring

“…AE of the rock under loading is irreversible, i.e., it will not occur noticeably until the loading stress magnitude exceeds that of the maximum stress in the loading history. This feature is termed the Kaiser effect, which represents the memory of the rock to the loading history (maximum stress or strain) [13][14][15][16][17][18][19]. Many defects, such as cracks, pores and particles, exist in the rock.…”

Optimizing Signal De-Noising Algorithm for Acoustic Emission Leakage of Wavelet

“…The sampled signal in every experiment demonstrates a feature of randomness. So in order to acquire better denoising effects, a dual self-adaptive lifting wavelet transformation algorithm is adopted to conduct de-noising processing which is to adopt self-adaptive filtering method in both updating link and predicting link [19].…”