Effect of Stress-Strain Conditions on Physical Precursors and Failure Stages Development in Rock Samples

Abstract

Precursory stages of failure development in large rock samples were studied and simultaneous observations of the space-time variation of several physical fields were carried out under different stress-strain states. The failure process was studied in detail. A hierarchical structure of discreet rock medium was obtained after loading. It was found that the moisture reduced the rock strength, increased the microcrack distribution and influenced the shape of the failure physical precursors. The rise in temperature up to 400 °C affected the physical precursors at the intermediate and final stages of the failure. Significant variations were detected in the acoustic and electromagnetic emissions. The coalescence criterion was slightly depending on the rock moisture and temperature effect. The possibility of identifying the precursory stage of failure at different strain conditions by means of a complex parameter derived from the convolution of physical recorded data is shown. The obtained results point out the efficiency of the laboratory modelling of seismic processes.

Some Probabilistic and Statistical Properties of the Seismic Regime of Zemmouri (Algeria) Seismoactive Zone

“…x ¦ , with l i the size of the crack. The exact value of the calescence criterion is K * = 3.8, which constitutes the threshold of the transition from the stage of crack accumulation to their start to coalesce and the formation ensembles of clusters in the cracked body (Baddari et al 2015). We will use K sr instead of K to characterize the crack concentration parameter of the seismogenic region.…”

“…A quasi-invariance of K sr is noted for zones which are far from epicenters, which confirms the hypothesis of spatial localization of SE in the level of the rupture zone. The values of K sr , before the macrorupture, calculated for the geophysical medium at different scales, are situated in the interval 3-7 (Baddari et al 2015, Zavyalov 2006.…”

“…Baddari et al (2013) presented the results of estimation of seismic moment values of a prescribed exceedence probability of the seismoactive zone of Zemmouri in Algeria using the moment magnitude distribution. Physical and statistical models were provided to study the earthquake clustering phenomenon (Kanamori 2004, Aitouche et al 2013, Baddari et al 2015. The principal approach in predicting macrofailure in relation to earthquake forecasting was based on the Poisson law (Zavyalov 2006, Baddari et al 2011.…”

Evaluation of the Influence of the Location Solid-State Inclusions on the Amplitude-Frequency Characteristics under Pulsed Acoustic Excitation in the Process of Uniaxial Compression

“…But on the other hand, acoustic impulses arising in the process of fracture development can excite electromagnetic signals on electrical double layers of defects, which can be recorded by equipment. In addition, acoustic impulses, when externally exposed on the controlled material or product, can also excite electromagnetic signals on electrical double layers of defects [5][6][7][8][9][10][11]. At the same time, contact reception of signals is not necessary, as is the case with acoustic sounding.…”