Study on chaos features of crack network evolution in coal-rock fracturing

2016 ◽  
Vol 16 (3) ◽  
pp. 563-573 ◽  
Author(s):  
Tingting Wang ◽  
Wanchun Zhao ◽  
Dan Zhao ◽  
Dongfeng Jiang
2021 ◽  
Vol 25 (6 Part B) ◽  
pp. 4423-4429
Author(s):  
Hai-Xiao Lin ◽  
Qiu-Yu Pan ◽  
Bang-Hua Yao ◽  
Wen-Long Shen ◽  
Feng Yang

Based on the characteristics of mechanical response of coal rock under loading, an elastic-brittle damage constitutive relation of coal rock has been proposed, which has been extended to the 3-D stress state, based on the geological strength index. Besides, a numerical calculation method based on the elastic-brittle damage the?ory has been developed, by analyzing the seepage-stress coupling effect. Then, a computing program for fracture network transformation has been composed to perform numerical simulation of forming process of coal rock under different working conditions, by the APDL language in the ANSYS software platform. The mechanical mechanism of fracture network forming process of coal rock has been further analyzed.


2018 ◽  
Vol 15 (2) ◽  
pp. 280-289 ◽  
Author(s):  
Xing-Li Zhang ◽  
Rui-Sheng Jia ◽  
Xin-Ming Lu ◽  
Yan-Jun Peng ◽  
Wei-Dong Zhao

2021 ◽  
Vol 2021 ◽  
pp. 1-14
Author(s):  
Pengfei Wu ◽  
Jianlong Wang ◽  
Xiaofei Luo ◽  
Rujun Mo ◽  
Yaoqing Hu ◽  
...  

Although hydraulic fracturing has been one of the primary stimulation methods for coal-bed methane (CBM) exploration, it is difficult to be applied in soft and low-permeability coal seams due to the instability of wells in such geological structures. In order to solve the problem, an idea of indirect fracturing is proposed, that is, fractures are initiated in stable and hard rocks and then propagated to coal seams in which crack networks can be formed. To verify the feasibility of such an approach, the true triaxial hydraulic fracturing experiments were conducted using two-dimensional and three-dimensional coal-rock combination samples, respectively. This study investigates the fracture patterns, pressure variation, and fracture morphology. The results show that in the process of fracture propagation from sandy mudstones to coals, the strain energy release rate in the sandy mudstones is 10.69∼25.53 times greater than that in the coal. When the fracture has a tendency to deflect toward the lower strength coal strata, under the condition of large K2/K1, the deflection criterion will be met first and the fracture will deflect and grow into the coal strata. In addition, the complex crack network can be generated when the hydrofracture intersects the coal-rock interface and the fracture pattern is analyzed.


2001 ◽  
Vol 1 (3) ◽  
pp. 145-158 ◽  
Author(s):  
D. Kiyashchenko ◽  
V. Troyan

Abstract. Several methods are presently suggested for investigating pre-earthquake evolution of the regions of high tectonic activity based on analysis of the seismicity spatial distribution. Some precursor signatures are detected before strong earthquakes: decrease in fractal dimension of the continuum of earthquake epicenters, cluster formation, concentration of seismic events near one of the nodal planes of the future earthquake, and others. In the present paper, it is shown that such peculiarities are typical of the evolution of the shear crack network under external stresses in elastic bodies with inhomogeneous distribution of strength. The results of computer modeling of crack network evolution are presented. It is shown that variations of the fractal dimension of the earthquake epicenters’ continuum and other precursor signatures contain information about the evolution of the destruction process towards the main rupture.


2018 ◽  
Vol 11 ◽  
pp. 39-45 ◽  
Author(s):  
S.N. Reshetnyak ◽  
◽  
Yu.M. Maksimenko ◽  
Keyword(s):  

Author(s):  
M. S. Bugaeva ◽  
O. I. Bondarev ◽  
N. N. Mikhailova ◽  
L. G. Gorokhova

Introduction. The impact on the body of such factors of the production environment as coal-rock dust and fluorine compounds leads to certain shift s in strict indicators of homeostasis at the system level. Maintaining the relative constancy of the internal environment of the body is provided by the functional consistency of all organs and systems, the leading of which is the liver. Organ repair plays a crucial role in restoring the structure of genetic material and maintaining normal cell viability. When this mechanism is damaged, the compensatory capabilities of the organ are disrupted, homeostasis is disrupted at the cellular and organizational levels, and the development of the main pathological processes is noted.The aim of the study is to compare the morphological mechanisms of maintaining structural homeostasis of the liver in the dynamics of the impact on the body of coal-rock dust and sodium fluoride.Materials and methods. Experimental studies were conducted on adult white male laboratory rats. Features of morphological mechanisms for maintaining structural homeostasis of the liver in the dynamics of exposure to coal-rock dust and sodium fluoride were studied on experimental models of pneumoconiosis and fluoride intoxication. For histological examination in experimental animals, liver sampling was performed after 1, 3, 6, 9, 12 weeks of the experiment.Results. The specificity of morphological changes in the liver depending on the harmful production factor was revealed. It is shown that chronic exposure to coal-rock dust and sodium fluoride is characterized by the development of similar morphological changes in the liver and its vessels from the predominance of the initial compensatory-adaptive to pronounced violations of the stromal and parenchymal components. Long-term inhalation of coal-rock dust at 1–3 weeks of seeding triggers adaptive mechanisms in the liver in the form of increased functional activity of cells, formation of double-core hepatocytes, activation of immunocompetent cells and endotheliocytes, ensuring the preservation of the parenchyma and the general morphostructure of the organ until the 12th week of the experiment. Exposure to sodium fluoride leads to early disruption of liver compensatory mechanisms and the development of dystrophic changes in the parenchyma with the formation of necrosis foci as early as the 6th week of the experiment.Conclusions. The study of mechanisms for compensating the liver structure in conditions of long-term exposure to coal-rock dust and sodium fluoride, as well as processes that indicate their failure, and the timing of their occurrence, is of theoretical and practical importance for developing recommendations for the timely prevention and correction of pathological conditions developing in employees of the aluminum and coal industry.The authors declare no conflict of interests.


Author(s):  
А. Molodetskyy ◽  
◽  
О. Gladkaya ◽  
V. Slyusarev ◽  
◽  
...  

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