Experimental Study on Mechanical and Acoustic Emission Characteristics of Rock Samples under Different Stress Paths

Qin, Tao; Sun, Hongru; Liu, Heng; Zhang, Junwen; Li, Tao; Liu, Gang; Liu, Zhenwen

doi:10.1155/2018/4813724

Cited by 11 publications

(9 citation statements)

References 9 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Regarding the initial axial pressure of unloading, Liu et al [13] selected 50% of the conventional triaxial compressive strength and the corresponding confining pressure, whereas other researchers often adopted 60% and 80% [14][15][16], 70% [17][18][19][20], 80-90% [21], and 15-90% [22]. Most researchers selected 80% of the peak strength as the loaded axial pressure in unloading tests [23][24][25][26]. Details of studies discussed above can be viewed in Table 1.…”

mentioning

confidence: 99%

Elastic-Plastic Threshold and Rational Unloading Level of Rocks

Guo

2019

Applied Sciences

View full text Add to dashboard Cite

During loading and unloading test, various rocks manifest different stress values of elastic-plastic transformation. This study proposes to include axial pressure increment ratio in the conventional triaxial compression test to evaluate different variables (nominal elastic modulus, nominal Poisson's ratio, strain, and energy). The relationships among various factors including variables, the stress level of initial confining stress and axial pressures, were analyzed by analyzing the stress-strain plot record obtained from testing various rocks. The extreme value point of the deformation parameter, also known as the elastic-plastic threshold, was analyzed. In addition, the elastic-plastic thresholds were later used as unloading points during the unloading tests. Under the same confining condition, different rocks demonstrated different unloading levels. Furthermore, a linear correlation was observed between unloading levels and changing confining pressures, and the gradient is mainly related to the types of rocks. During the unloading tests of rocks, the rational unloading level is recommended to be no higher than the stress level at the elastic-plastic threshold under the corresponding confining pressure. Appl. Sci. 2019, 9, 3164 2 of 15 and the unloading level has no significant effect on the energy evolution process. Zhang [11] and Zhu [12] considered that the unloading stress level mitigated possible damage within rocks during the unloading damage stage. Regarding the initial axial pressure of unloading, Liu et al. [13] selected 50% of the conventional triaxial compressive strength and the corresponding confining pressure, whereas other researchers often adopted 60% and 80% [14][15][16], 70% [17][18][19][20], 80-90% [21], and 15-90% [22]. Most researchers selected 80% of the peak strength as the loaded axial pressure in unloading tests [23][24][25][26]. Details of studies discussed above can be viewed in Table 1. However, mentioned studies failed to consider the effects of the initial axial pressure during exploring the effects of unloading on rock failures.

show abstract

mentioning

confidence: 99%

Elastic-Plastic Threshold and Rational Unloading Level of Rocks

Guo

2019

Applied Sciences

View full text Add to dashboard Cite

show abstract

“…(1) Initially, loading to the hydrostatic pressure σ 1 � σ 2 � σ 3 at a rate of 0.05 MPa/s. (2) en, the axial pressure was applied at a rate of 0.05 MPa/s to about 80% of the ultimate stress under its confining pressure condition. e ultimate stress was determined by the conventional triaxial compression experiment as shown in Table 1.…”

Section: Experimental Approachmentioning

confidence: 99%

“…at is, the rock mass undergoes the mining dynamics process from the original rock stress, loading, and unloading to destruction. e practice of underground rock engineering shows that most of the rock failures occur in the unloading state of surrounding rock [1,2]. e study on the failure law of rock damage under unloading confining pressure is of great significance for revealing the mechanical properties and fracture mechanism of rock under the unloading state.…”

Section: Introductionmentioning

confidence: 99%

Energy Evolution and Acoustic Emission Characteristics of Sandstone Specimens under Unloading Confining Pressure

Qin

Duan

Sun

et al. 2019

Shock and Vibration

Self Cite

View full text Add to dashboard Cite

The acoustic emission characteristics of rock specimens under different initial unloading confining pressures were tested to obtain the damage and rupture characteristics of the sandstone unloading confining pressure path. The CT scan and three-dimensional reconstruction of the fractured rock specimens were carried out to study the differences of energy evolution and acoustic emission characteristics during the failure of sandstone under different initial unloading pressures. The results show that the unloading confining pressure has a significant influence on the deformation and failure of the rock. There is a significant yielding platform for the circumferential strain and the bulk strain at the peak of the unloading pressure. The larger the initial unloading pressure is, the greater the axial absorption strain energy, the dissipative energy, and the elastic strain energy are at the peak point. After the stress peak point, the elastic strain can be quickly converted into the dissipative energy for rock damage. The elastic energy released from the moment of rock failure under high confining pressure is more concentrated. The acoustic emission ringing and b value characteristic parameters of the rock have a good correlation with the internal energy evolution of the rock, which better reflects the progressive damage of the rock under low stress and the sudden failure of high-stress unloading.

show abstract

“…Fractured rock mass is the main occurrence form of rock mass in nature, its strength and deformation failure are significantly affected by the generation and expansion of cracks, and the mechanical behavior of rock mass changes with the change of stress paths [1][2][3]. Because of the influence of engineering disturbance, in situ stress state changes not only the stress magnitude, but also the rotation of the principal stress direction, which is an important factor in the research of inducing rock mass stress concentration and rock strength degradation.…”

Section: Introductionmentioning

confidence: 99%

The Mechanism of Rock Mass Crack Propagation of Principal Stress Rotation in the Process of Tunnel Excavation

Chang

Hua

Zhang

et al. 2021

Shock and Vibration

View full text Add to dashboard Cite

Rock excavation has experienced complex stress paths. The development of the original crack under the path of principal stress magnitude and principal stress direction is a key scientific problem that needs to be solved in rock underground engineering. The principal stress magnitude dominates the initiation and propagation of the crack and increases rock damage under the action of principal stress rotation. In this study, the theoretical calculation and numerical analysis method have been combined with the crack propagation conditions to study the stress-driven mechanism of brittle rock crack propagation under principal stress rotation. The results show that the “relative initial angle” of crack angle is being updated in time during the principal stress rotation process; once the stress is rotated, it will become the next initial crack angle; the crack propagation direction is deviated under the applied shear load, and it is always in the direction of minimum shear load, leading to a certain degree of inhibition of crack propagation depth in the initial direction. According to the results of numerical simulation, the effect of principal stress rotation caused by mining excavation is obvious and has a certain range of influence depth, the stress of surrounding rock of roadway is the highest within the depth range of 1∼2 m, and the maximum principal stress is as high as 26.89 MPa. The rotation of principal stress direction on the roadway surrounding rock surface is the strongest, which makes the surrounding rock more fragmented, and the middle principal stress and the maximum principal stress rotate about 90° counterclockwise along the Ox axis. Studying the action mechanism of principal stress rotation on fractured rock masses can provide scientific basis for geotechnical engineering design and rock mass surrounding support.

show abstract

Experimental Study on Mechanical and Acoustic Emission Characteristics of Rock Samples under Different Stress Paths

Cited by 11 publications

References 9 publications

Elastic-Plastic Threshold and Rational Unloading Level of Rocks

Elastic-Plastic Threshold and Rational Unloading Level of Rocks

Energy Evolution and Acoustic Emission Characteristics of Sandstone Specimens under Unloading Confining Pressure

The Mechanism of Rock Mass Crack Propagation of Principal Stress Rotation in the Process of Tunnel Excavation

Contact Info

Product

Resources

About