scholarly journals Experimental Research into the Evolution of Permeability in a Broken Coal Mass under Cyclic Loading and Unloading Conditions

2019 ◽  
Vol 9 (4) ◽  
pp. 762 ◽  
Author(s):  
Bo Li ◽  
Quanle Zou ◽  
Yunpei Liang
Keyword(s):  
Cyclic Loading ◽  
Coal Sample ◽  
Stress Sensitivity ◽  
Coal Mass ◽  
Repeated Loading ◽  
Particle Deformation ◽  
Cyclic Loading And Unloading ◽  
Coal Particles ◽  
Loading And Unloading ◽  
Broken Coal Mass

The permeability characteristics of a broken coal mass under repeated loading and unloading conditions exert significance on spontaneous combustion of coal in goaf during the mining of coal seam groups. Considering this, by using the seepage test system for broken coal-rock mass, seepage tests under cyclic loading and unloading conditions, were carried out on broken coal masses. The test results show that the fitting curves between permeability and effective stress, strain and porosity are a logarithmic function, cubic function and power function, respectively. Besides, the permeability of a broken coal sample under cyclic loading and unloading conditions is determined by its porosity, which conforms to the cubic law. With increased cyclic loading and unloading times, the permeability loss, stress sensitivity and the crushing amount of the broken coal sample were gradually reduced, but the particle size gradation of the broken coal sample gradually became better. During one loading and unloading cycle, the stress sensitivity of the permeability of coal samples in the loading stage was far higher than that in the unloading stage. In the loading stage, the re-arrangement, breakage and compressive deformation of coal particles can lead to a reduction in porosity, consequently resulting in a decreased permeability. In the unloading stage, only the permeability reduction of coal samples due to particle deformation can be recovered.

scholarly journals Variation law of coal permeability under cyclic loading and unloading

2019 ◽  
Vol 23 (3 Part A) ◽  
pp. 1487-1494 ◽  
Author(s):  
Jingna Guo ◽  
Jiangfeng Liu ◽  
Qiang Li ◽  
Chen Xu ◽  
Zhanqing Chen ◽  
...  
Keyword(s):  
Cyclic Loading ◽  
Plastic Flow ◽  
Coal Sample ◽  
Shear Failure ◽  
Axial Strain ◽  
Crack Opening ◽  
Coal Pillar ◽  
Loading Path ◽  
Cyclic Loading And Unloading ◽  
Loading And Unloading

In the excavation process, the coal pillar will undergo shear failure due to repeated loading and unloading from mining stress. Meanwhile, plastic flow will occur after shear failure. The permeability change of the coal pillar under plastic flow is closely related to the loading path. Through a permeability test of the coal sample after shear yielding under cyclic loading and unloading conditions, the variation law of permeability of a coal seam under plastic flow was obtained. The results show that the permeability of the coal sample increases as the axial strain decreases during the unloading phase. During the loading phase, as the axial strain increases, the permeability of the coal sample decreases. Scanning electron microscope tests show that the crack opening is larger at lower confining pressures. As the confining pressure increases, the crack opening decreases and moves toward the middle of the sample.

Analysis of cyclic shear characteristics of reinforced soil interfaces under cyclic loading and unloading

2021 ◽  
Author(s):  
Meng-jie Ying ◽  
Jun Wang ◽  
Fei-yu Liu ◽  
Jing-ting Li ◽  
Shu-qi Chen
Keyword(s):  
Cyclic Loading ◽  
Reinforced Soil ◽  
Cyclic Shear ◽  
Cyclic Loading And Unloading ◽  
Shear Characteristics ◽  
Loading And Unloading

Effects of Confining Pressure and Temperature on the Energy Evolution of Rocks Under Triaxial Cyclic Loading and Unloading Conditions

2021 ◽  
Author(s):  
Qing-bin Meng ◽  
Jiang-feng Liu ◽  
Bing-xiang Huang ◽  
Hai Pu ◽  
Jiang-yu Wu ◽  
...  
Keyword(s):  
Cyclic Loading ◽  
Confining Pressure ◽  
Energy Evolution ◽  
Cyclic Loading And Unloading ◽  
Loading And Unloading

Adjustable buttons for ACL graft cortical fixation partially fail with cyclic loading and unloading

2018 ◽  
Vol 27 (8) ◽  
pp. 2530-2536 ◽  
Author(s):  
J. Glasbrenner ◽  
C. Domnick ◽  
M. J. Raschke ◽  
T. Willinghöfer ◽  
C. Kittl ◽  
...  
Keyword(s):  
Cyclic Loading ◽  
Acl Graft ◽  
Cyclic Loading And Unloading ◽  
Loading And Unloading

Effects of Detwinning on the Inelasticity of AZ31B Sheets During Cyclic Loading and Unloading

2018 ◽  
Vol 10 (09) ◽  
pp. 1850095 ◽  
Author(s):  
H. Wang ◽  
D. Tang ◽  
D. Y. Li ◽  
Y. H. Peng ◽  
P. D. Wu
Keyword(s):  
Cyclic Loading ◽  
Magnesium Alloys ◽  
Plasticity Model ◽  
Inelastic Behavior ◽  
Deformation History ◽  
Cyclic Loading And Unloading ◽  
Polycrystal Plasticity ◽  
Self Consistent ◽  
Loading And Unloading ◽  
Previous Loading

Magnesium alloys exhibit significant inelastic behavior during unloading, especially when twinning and detwinning are involved. It is commonly accepted that noteworthy inelastic behavior will be observed during unloading if twinning occurs during previous loading. However, this phenomenon is not always observed for Mg sheets with strong rolled texture. Therefore, the inelasticity of AZ31B rolled sheets with different rolled textures during cyclic loading-unloading are investigated by elastic viscoplastic self-consistent polycrystal plasticity model. The incorporation of the twinning and detwinning model enables the treatment of detwinning, which plays an important role for inelastic behavior during unloading. The effects of texture, deformation history, and especially twinning and detwinning on the inelastic behaviors are carefully investigated and found to be remarkable. The simulated results are in agreement with the available experimental observations, which reveals that the inelastic behavior for strongly rolled sheets is very different than the extruded bars.

scholarly journals Damage and fractal evolution trends of sandstones under constant-amplitude and tiered cyclic loading and unloading based on acoustic emission

2019 ◽  
Vol 15 (7) ◽  
pp. 155014771986102
Author(s):  
Dongxu Liang ◽  
Nong Zhang ◽  
Lixiang Xie ◽  
Guangming Zhao ◽  
Deyu Qian
Keyword(s):  
Acoustic Emission ◽  
Cyclic Loading ◽  
Damage Evolution ◽  
Damage Accumulation ◽  
Fractal Dimensions ◽  
Damage Variable ◽  
Constant Amplitude ◽  
Kaiser Effect ◽  
Cyclic Loading And Unloading ◽  
Loading And Unloading

It is of significance to study the damage and destruction of rock under cyclic loading in geotechnical engineering. We determined the trends in damage evolution of sandstone under constant-amplitude and tiered cyclic loading and unloading under uniaxial compression. The results of the study show that (1) the variation of acoustic-emission events was consistent with the stress curves and 89% of all acoustic-emission events occurred during the cycling stages. The observed Kaiser effect was more notable in tiered cycling. (2) The damage variable increased sharply in the cycling stages and its increment was 0.07 higher for tiered cycling than constant-amplitude cycling. Sandstone exhibited greater damage under tiered cyclic loading and unloading. (3) Equations for the evolution of the damage variable under the two cycle modes were obtained by fitting of experimental data. (4) The fractal dimensions of the constant-amplitude cycle were larger than those of the tiered cycle. The process of damage and destruction presents a trend of reducing fractal dimension. The damage accumulation of sandstone under tiered cycling was faster than under constant-amplitude cycling. These results provide references for damage and early warning of rock under both constant-amplitude and tiered cyclic loading and unloading.

Experimental Study of Mechanical Behavior of Interlayer Staggered Zone under Cyclic Loading and Unloading Condition

2020 ◽  
Vol 20 (3) ◽  
pp. 04019187 ◽  
Author(s):  
Shuqian Duan ◽  
Quan Jiang ◽  
Dingping Xu ◽  
Guofeng Liu
Keyword(s):  
Experimental Study ◽  
Cyclic Loading ◽  
Mechanical Behavior ◽  
Cyclic Loading And Unloading ◽  
Loading And Unloading

Finite Element Modeling of a Thin Circular Disc Manufactured by Forming Process used in Cyclic Loading and Unloading Applications

2020 ◽  
Vol 22 ◽  
pp. 2990-3000
Author(s):  
AjithRamesh ◽  
Rojin Mathews ◽  
Anoop Pillai A ◽  
Unnikrishnan Divakaran
Keyword(s):  
Finite Element ◽  
Cyclic Loading ◽  
Finite Element Modeling ◽  
Circular Disc ◽  
Forming Process ◽  
Element Modeling ◽  
Cyclic Loading And Unloading ◽  
Loading And Unloading

scholarly journals Research on the Mechanical Characteristics of Cyclic Loading and Unloading of Rock Based on Infrared Thermal Image Analysis

2021 ◽  
Vol 2021 ◽  
pp. 1-16
Author(s):  
Lewen Wu ◽  
Keping Zhou ◽  
Feng Gao ◽  
Zhongyuan Gu ◽  
Chun Yang
Keyword(s):  
Temperature Field ◽  
Cyclic Loading ◽  
Infrared Radiation ◽  
Energy Analysis ◽  
Heating Zone ◽  
Characteristic Analysis ◽  
Temperature Zone ◽  
Energy Accumulation ◽  
Cyclic Loading And Unloading ◽  
Loading And Unloading

In the operations of underground rock engineering, such as mining, the formation of goafs is often accompanied by unloading and energy effects. In this study, a cyclic loading and unloading stress test is carried out to analyze the strength characteristics of the loaded samples under different loading and unloading ranges as well as different numbers of cycles. The rock force is accompanied by substantial energy changes. To better fit the energy analysis under cyclic loading and unloading conditions, thermal infrared radiation characteristic analysis is performed during rock loading and unloading. An infrared radiation camera is adopted to detect the infrared characteristics of the rock force process after cyclic loading and unloading. Multiangle detection is implemented on the temperature, temperature field, and frequency histogram. The analysis shows that cyclic loading and unloading first strengthen and then weaken the rock. Moreover, the failure caused by the local stress concentration leads to a sharp increase in the temperature. There are significant temperature fluctuations before and after failure, and the temperature field after failure can be divided into three zones, namely, the normal temperature zone, heating zone, and mutational temperature zone, to comprehensively reflect that rock compression failure which is accompanied by the process of energy accumulation and release. On the basis of infrared energy analysis, the index of the energy release rate is introduced, and the loading and unloading analysis model is constructed. The research results reveal that rock failure is accompanied by the process of energy accumulation and release, which provides evidence for the analysis of the spatial stability of the rock mass under cyclic loading and unloading conditions and engineering excavation.

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