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Abstract
In the real environment, besides static load, rock is more affected by cyclic load. There is a large difference in the mechanical properties exhibited by rocks under cyclic and static loading. Therefore, it is particularly necessary to investigate the mechanical characteristics of rock subjected to cyclic loading. These parameters of rock, acoustic emission (AE) and resistivity, are both sensitive to the failure process of rock, and they are complementary to the different stages of rock damage. Therefore, in this paper, the AE characteristics and resistivity properties of sandstone subjected to constant‐amplitude cyclic loading and unloading were experimentally investigated using a typical sandstone in Chongqing. The same three‐stage pattern was found for the AE evolution of sandstones during constant‐amplitude cyclic loading. Initial evolution stage: the rock deformation is fast with strong changes in the AE signal. The rock deformation developed slowly while the changes of the AE signal were stable in the constant velocity evolution stage. The rock deformation developed dramatically while the AE signal became more intense in accelerated evolution stage. The change in resistivity is characterized by a rapid decrease during the loading stage and a rapid rebound during the unloading stage. Overall, from the beginning of the cycle to the end of the cycle, the resistivity of the sandstone showed a general trend of gradual decrease, until the sudden increase in resistivity at the time of damage. Finally, a damage model based on AE parameters and resistivity was constructed by combining damage mechanics.
Highlights
Rock mass is a discontinuous medium with a complex internal structure
Test Results and Analysis e number of AE ringing refers to the number of oscillations caused by the oscillating wave generated by the AE signal crossing the voltage threshold, which has been widely used in the activity evaluation of AE. e number of acoustic emission rings produced per unit time in a rock sample can reflect the state of damage and deformation of the internal structure of the sample when subjected to cyclic stress. e more the number of AE ringing counts in unit time, the more serious the damage of the rock sample
The characteristic parameter method is widely used in processing AE signals [28]. e AE characteristic parameters contain a lot of information about the material damage evolution process, and the characteristic parameter method is to reflect the characteristics of AE signals by analyzing and processing several simplified waveform characteristic parameters
Summary
Rock mass is a discontinuous medium with a complex internal structure. Many studies [1, 2] have shown that the phenomenon of particle crushing often occurs in conjunction with rock particle compaction, and a number of experimental methods have been carried out to analyze the crushing behaviour of rock particles. Ma et al [3, 4] used laboratory, theoretical, and field studies followed by experimental data to calculate and analyze the evolution of the deformation behaviour of gangue grains during compression tests. Alnedawi et al [5] monitored the effect of loading frequency on rock deformation characteristics by using repeated loading triaxial tests. There are a series of studies on the evolution of rock damage. Hu et al [6] performed triaxial tests on granular rocks under cyclic stress paths and discussed the linear evolution of the plastic work with respect to the critical state. Under the action of cyclic loading, rock damage gradually accumulates until the final appearance of fatigue degradation characteristics, which have a negative impact on the stability of the project and increase
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