Mechanical Behavior, Energy Release, and Crack Distribution Characteristics of Water-Saturated Phyllite under Triaxial Cyclic Loading

Many geological engineering hazards are closely related to the dynamic mechanical behaviors of rock materials. However, the dynamic mechanical behaviors of phyllite are less studied. In this study, we have carried out a series of triaxial cyclic tests on dry and water-saturated phyllite by employing the MTS 815 servohydraulic testing system and AE testing equipment to reveal the mechanical behavior, energy release, and crack distribution characteristics of phyllite. Results show that phyllite is a water-sensitive rock. Water and cyclic loading substantially affect the compressive strength, crack damage stress, deformation parameters, dilatancy, energy release, and crack distribution characteristics of phyllite. Furthermore, based on the dissipated energy, a new damage variable for phyllite is established. The critical damage variable for phyllite is approximately 0.80; this variable can be used as an index to predict the failure of phyllite. The water saturation effect of phyllite is very obvious; that is, it results in the weakness of mechanical properties of phyllite and changes the AE energy release and crack distribution characteristics of phyllite. This research can provide guidance for engineering construction and disaster prevention and control.

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Analysis the characteristic of energy and damage of coal-rock composite structure under cycle loading

10.21203/rs.3.rs-348847/v1 ◽

2021 ◽

Author(s):

Tan Li ◽

Guangbo Chen ◽

Zhongcheng Qin ◽

Qinghai Li

Keyword(s):

Cyclic Loading ◽

Elastic Energy ◽

Composite Structure ◽

Calculation Method ◽

Composite Structures ◽

Damage Variable ◽

Dissipated Energy ◽

Height Ratio ◽

Coal Rock ◽

The Stability

Abstract The stability of coal-rock composite structures is of great significance to coal mine safety production. To study the stability and deformation failure characteristics of the coal-rock composite structure, the uniaxial cyclic loading tests of the coal-rock composite structures with different coal-rock height ratios were carried out. Lithology and coal-rock height ratio play an important role in the energy dissipation of coal-rock composite structures. The higher the coal-rock height ratio, the greater the average elastic energy and dissipated energy produced per cycle of coal-rock composite structures, the smaller the total elastic energy and dissipated energy produced in the process of cyclic loading. Based on the difference of damage variables calculated by dissipative energy method and acoustic emission method, a more sensitive joint calculation method for calculating damage variable was proposed. The joint damage variable calculation method can more accurately and sensitively reflect the damage of coal-rock composite structure under cyclic loading. The macroscopic crack first appears in the coal specimen in the coal-rock composite structure, the degree of broken coal specimens in the composite structure is inversely proportional to the coal-rock height ratio. The strength and deformation characteristics of the coal-rock composite structure are mainly affected by coal sample in the composite structure.

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Dynamic Mechanical Behavior of Dry and Water Saturated Igneous Rock with Acoustic Emission Monitoring

Shock and Vibration ◽

10.1155/2018/2348394 ◽

2018 ◽

Vol 2018 ◽

pp. 1-14 ◽

Cited By ~ 5

Author(s):

Jun Guo ◽

Guo-rui Feng ◽

Ting-ye Qi ◽

Pengfei Wang ◽

Jian Yang ◽

...

Keyword(s):

Acoustic Emission ◽

Cyclic Loading ◽

Mechanical Behavior ◽

Igneous Rock ◽

Water Injection ◽

Brittle Behavior ◽

Cyclic Loading And Unloading ◽

Cyclic Loading Tests ◽

Water Saturated ◽

Water Contents

The uniaxial cyclic loading tests have been conducted to study the mechanical behavior of dry and water saturated igneous rock with acoustic emission (AE) monitoring. The igneous rock samples are dried, naturally immersed, and boiled to get specimens with different water contents for the testing. The mineral compositions and the microstructures of the dry and water saturated igneous rock are also presented. The dry specimens present higher strength, fewer strains, and rapid increase of AE count subjected to the cyclic loading, which reflects the hard and brittle behavior and strong burst proneness of igneous rock. The water saturated specimens have lower peak strength, more accumulated strains, and increase of AE count during the cyclic loading. The damage of the igneous rocks with different water contents has been identified by the Felicity Ratio Analysis. The cyclic loading and unloading increase the dislocation between the mineral aggregates and the water-rock interactions further break the adhesion of the clay minerals, which jointly promote the inner damage of the igneous rock. The results suggest that the groundwater can reduce the burst proneness of the igneous rock but increase the potential support failure of the surrounding rock in igneous invading area. In addition, the results inspire the fact that the water injection method is feasible for softening the igneous rock and for preventing the dynamic disasters within the roadways and working faces located in the igneous intrusion area.

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Effects of Microstructure and Shock Prestrain on the Dynamic Mechanical Behavior of Ti-6Al-4V Alloy

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.837.51 ◽

2020 ◽

Vol 837 ◽

pp. 51-57

Author(s):

Shi Meng Zhou ◽

Zhi Wei Wang ◽

Yu Ren

Keyword(s):

Mechanical Behavior ◽

Stress Amplitude ◽

Lamellar Microstructure ◽

Uniaxial Stress ◽

Strengthening Effect ◽

Enhancement Ratio ◽

Mechanical Behaviors ◽

Dynamic Mechanical ◽

Impact Stress ◽

Dynamic Mechanical Behavior

Ti–6Al–4V alloy (Ti64) with different microstructures was first preshocked at ~6–13 GPa and then compression reloaded at 4×103s-1 to investigate the effect of microstructure and shock prestrain on the dynamic mechanical behavior of this alloy. The strengthening effect caused by shock prestrain is weaker than that introduced by the uniaxial stress compression during dynamic reloading process regardless of microstructure type and impact stress amplitude. However, the shock-induced enhancement ratio is higher in Ti64 having bimodal microstructures or the lamellar microstructure with wide α-platelets. These mechanical behaviors exhibited by postshock materials are closely related to the shock-induced microstructure evolution. Dislocations more tend to nucleate and interact in large-sized α phases such as equiaxed primary α and wide α-platelets. The generation of high-density micro-defects during the propagation of shock waves results in the improvement of strength but degradation of ductility of Ti64 during dynamic reloading process.

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Dynamic mechanical behavior and fatigue damage evolution of sandstone under cyclic loading

International Journal of Rock Mechanics and Mining Sciences ◽

10.1016/j.ijrmms.2017.03.003 ◽

2017 ◽

Vol 94 ◽

pp. 82-89 ◽

Cited By ~ 32

Author(s):

Bi Sun ◽

Zhende Zhu ◽

Chong Shi ◽

Zhihua Luo

Keyword(s):

Cyclic Loading ◽

Mechanical Behavior ◽

Fatigue Damage ◽

Damage Evolution ◽

Dynamic Mechanical ◽

Dynamic Mechanical Behavior

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Study on Permeability of Deep-Buried Sandstone under Triaxial Cyclic Loads

Advances in Civil Engineering ◽

10.1155/2021/6635245 ◽

2021 ◽

Vol 2021 ◽

pp. 1-9

Author(s):

Mingqiang Sheng ◽

Awei Mabi ◽

Xigen Lu

Keyword(s):

Acoustic Emission ◽

Cyclic Loading ◽

Energy Density ◽

Damage Variable ◽

Dissipated Energy ◽

Peak Strain ◽

Rock Damage ◽

Cyclic Loading And Unloading ◽

Relative Strain ◽

Loading And Unloading

The triaxial cyclic loading and unloading test was carried out on a TAW-2000 rock mechanics to study the permeability characteristics of deep-buried sandstone. This paper analyzed the evolution laws of permeability, elastic modulus, rock damage, dissipated energy, and acoustic emission events of sandstone under different confining pressures. It also introduced the concept of relative strain and further discussed the relationship between relative strain and permeability. The test results showed that the permeability of sandstone under cyclic loading and unloading obviously experienced three stages. At a low strain level, the damage degree of sandstone was low. As a result, both the number of acoustic emission events and the proportion of the dissipated energy density were small. In this stage, with increasing the stress, the permeability decreased. With the increase of the relative strain, the propagation of fissure increased through rock interior and the damage of rock was accumulated. Consequently, the number of acoustic emission events grew slowly, and the proportion of dissipated energy density and the damage variable (D) increased gradually. In this stage, the permeability increases. As the axial strain reached the peak strain, the fissures developed into cracks and the rock failure happened. The number of acoustic emission events increased rapidly; both the proportion of the dissipated energy density and the damage variable (D) obtain the maximum value. In this stage, the permeability increased greatly. In this study, the point of fissure propagation of rock specimens was used as the point of demarcation. Before the fissures propagated, the permeability increased slowly and it was in accordance with a linear function. After the fissures propagated, the degree of rock damage increased, and the permeability increased in the form of an exponential function. The larger the confining pressure was, the smaller the relative strain corresponding to the point of fissure propagation was.

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Mechanical Behavior and Damage Evolution for Granite Subjected to Cyclic Loading

Advances in Materials Science and Engineering ◽

10.1155/2018/4312494 ◽

2018 ◽

Vol 2018 ◽

pp. 1-10 ◽

Cited By ~ 2

Author(s):

Zhiliang Wang ◽

Jikang Yao ◽

Nuocheng Tian ◽

Jingbin Zheng ◽

Peng Gao

Keyword(s):

Cyclic Loading ◽

Mechanical Behavior ◽

Damage Evolution ◽

Confining Pressure ◽

Test System ◽

Triaxial Tests ◽

Dissipated Energy ◽

Granite Sample ◽

Cycle Number ◽

Four Levels

This paper focuses on the mechanical behavior and damage evolution of Huashan granite subjected to cyclic loading. Four levels of confining pressure (0, 15, 25, and 35 MPa) were applied during cyclic axial loading by using a Rock Test System (MTS815) along with an acoustic emission (AE) monitoring device. Experimental results indicate that the number of AE activities is higher under cyclic triaxial loading compared to that under cyclic uniaxial loading. The measured stress-strain curves of both uniaxial and triaxial tests under cyclic loading are concave-up, but the degree of concavity is mild for the latter. As the cycle number rises, elastic modulus of the granite sample under different confining pressures increases. The slope of the peak strength versus confining pressure plot for the cyclic loading is larger than that for the monotonic loading. Besides, it is found that the dissipated energy increases with the increase of cyclic stress, but it hardly increases in proportion with the confining pressure. The damage parameters defined in terms of the plastic strain can be extended for the whole cyclic loading process, and they agree well with the energy-based damage parameters.

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Experimental Investigation of the Mechanical Behavior of Layer-Crack Specimens under Cyclic Uniaxial Compression

Symmetry ◽

10.3390/sym11040465 ◽

2019 ◽

Vol 11 (4) ◽

pp. 465

Author(s):

Wei-yao Guo ◽

Feng-hai Yu ◽

Yue Qiu ◽

Tong-bin Zhao ◽

Yun-liang Tan

Keyword(s):

Cyclic Loading ◽

Energy Density ◽

Mechanical Behavior ◽

Elastic Energy ◽

Peak Stress ◽

Dissipated Energy ◽

Strengthening Effect ◽

Input Energy ◽

Rock Bursts ◽

Number Of Cycles

It is generally acknowledged that the failure of the layer-crack structure is closely related to rock bursts (a layer-crack structure means a coal or rock rib that is cut by fractures that are parallel or sub-parallel to the surface of the rib). Understanding the mechanical behavior of the layer-crack structure under cyclic loading is beneficial for rock burst mitigation. This study experimentally investigated the influence of the geometry of vertical fissure (i.e., width, length and number) on the mechanical properties of layer-crack rock specimens. The results show that the sensitivity of parameters with respect to the geometry of the fissure from strong to weak is the number, length and width. First, the peak stress under cyclic loading increases by approximately 7.82%–17.35%, thereby exerting an obvious strengthening effect. Second, the fissure geometry slightly affects the energy evolution of the layer-crack specimen, i.e., the input energy density, elastic energy density and dissipated energy density all gradually increase with the increase of the number of cycles. However, when approaching a specimen failure, the increasing rates from quick to slow are the dissipated energy, input energy and elastic energy. Third, the damage variable of the layer-crack specimen shows a concave increasing trend with the increase of the number of cycles. When the number of cycles is equal, the damage increases with the increase of the number of fissures, but it decreases with the increase of the fissure length. Fourth, AE events occur shortly before specimen failures, but rapidly increase near the specimen failures. The accumulated AE events that lead to specimen failures decrease with the increase in the number of fissures. These results can provide some basic data for the research of rock bursts related to the failures of layer-crack structures.

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