scholarly journals Experimental Study of the Influence of Moisture Content on the Mechanical Properties and Energy Storage Characteristics of Coal

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Nan Liu ◽  
Chuanming Li ◽  
Ruimin Feng ◽  
Xin Xia ◽  
Xiang Gao
Keyword(s):  
Mechanical Properties ◽  
Moisture Content ◽  
Rock Burst ◽  
Elastic Energy ◽  
Coal Sample ◽  
Water Injection ◽  
Peak Stress ◽  
Peak Strain ◽  
Energy Index ◽  
The Impact

Rock burst occurs frequently as coal mining depth goes deeper, which seriously impacts the safety production of underground coal mines. Coal seam water injection is a technique commonly used to prevent and control such accidents. Moisture content is a critical factor tightly related to rock burst; however, an in-depth insight is required to discover their relationship. In this study, the influence of moisture content on the mechanical properties of coal and rock burst tendency is explored via multiple measurement techniques: uniaxial compression test, cyclic loading/unloading test, and acoustic emission (AE) test. These tests were performed on coal samples using the MTS-816 rock mechanics servo testing machine and AE system. The testing results showed that with the increase in moisture content, the peak strength and elastic modulus of each coal sample are reduced while the peak strain increases. The duration of the elastic deformation phase in the complete stress-strain curves of coal samples is shortened. As the moisture content increases, the area of hysteretic loop and elastic energy index W ET of each coal sample are reduced, and the impact energy index K E is negatively correlated with the moisture content, whereas dynamic failure time is positively correlated with the moisture content, but this variation trend is gradually mitigated with the continuous increase of moisture content. The failure of the coal sample is accompanied by the sharp increase in the AE ring-down count, whose peak value lags behind the peak stress, and the ring-down count is still generated after the coal sample reached the peak stress. With the increase in moisture content, the failure mode of the coal sample is gradually inclined to tensile failure. The above test results manifested that the strength of the coal sample is weakened to some extent after holding moisture, the accumulative elastic energy is reduced in case of coal failure, and thus, coal and rock burst tendency can be alleviated. The study results can provide a theoretical reference for studying the fracture instability of moisture-bearing coal and prevention of coal and rock burst by the water injection technique.

Research on the Mechanical Properties and Energy Consumption Transfer Law of Cement Tailings Backfill Under Impact Load

2021 ◽  
Vol 13 (5) ◽  
pp. 889-898
Author(s):  
Yong-Ye Mu ◽  
Xiang-Long Li ◽  
Jian-Guo Wang ◽  
Zhi-Gao Leng
Keyword(s):  
Mechanical Properties ◽  
Energy Transfer ◽  
Impact Load ◽  
Peak Stress ◽  
Peak Strain ◽  
Impact Compression ◽  
Average Strain Rate ◽  
Failure Morphology ◽  
The Stability ◽  
The Impact

The cemented tailings backfill (CTB), which plays a significant role in the stability of mine structure, is made of cement, tailings, and water in a certain proportion. When blasting and excavating an underground mine, the CTB will be disturbed by blasting. The impact load of blasting has an impact on the stability of the CTB, which is directly related to the safety of mine construction. The mechanical behaviour of CTB is generally affected by the cement-tailings ratio (C/T) and average strain rate (ASR). Therefore, a series of impact experiments were carried out on three CTB specimens with different C/T using a SHPB. Combined with the experimental results, this account reports studies on the effects of C/T and ASR on the mechanical properties of CTB, and on the energy transfer laws of CTB during impact compression. The research results show that when the ASR is less than 70 s−1, the peak stress and the peak strain have the same trend, and both of them continue to increase with the increase of ASR.When the ASR exceeds 70 s−1, as the ASR increases, the peak stress continues to increase, but the peak strain decreases gradually. Afterwards, the law of energy transfer of the CTB specimen was analyzed. It was found that as the incident energy increased, the energy reflection ratio of the CTB increased. Both the energy transmitted ratio and the energy dissipation ratio decreased. The volumetric energy showed a sharp increase first and then a trend Because of the slowly increasing trend. Finally, according to the failure morphology of the CTB, it is found that the ASR and the C/T together affect the failure of the CTB. The failure model of the CTB is mainly split failure and crush failure.

Comparison Analysis on the Mechanical Properties of HSC and NSC after the Action of High Temperatures

2014 ◽  
Vol 1014 ◽  
pp. 49-52
Author(s):  
Xiao Ping Su
Keyword(s):  
Mechanical Properties ◽  
High Temperature ◽  
High Temperatures ◽  
High Strength Concrete ◽  
Elasticity Modulus ◽  
Strain Curve ◽  
Peak Stress ◽  
High Strength ◽  
Peak Strain ◽  
Strength Concrete

With the wide application of high strength concrete in the building construction,the risk making concrete subject to high temperatures during a fire is increasing. Comparison tests on the mechanical properties of high strength concrete (HSC) and normal strength concrete (NSC) after the action of high temperature were made in this article, which were compared from the following aspects: the peak stress, the peak strain, elasticity modulus, and stress-strain curve after high temperature. Results show that the laws of the mechanical properties of HSC and NSC changing with the temperature are the same. With the increase of heating temperature, the peak stress and elasticity modulus decreases, while the peak strain grows rapidly. HSC shows greater brittleness and worse fire-resistant performance than NSC, and destroys suddenly. The research and evaluation on the fire-resistant performance of HSC should be strengthened during the structural design and construction on the HSC buildings.

The Comparison of the Loess Mechanical Properties under Plane Strain and Conventional Triaxial Experiments

2014 ◽  
Vol 919-921 ◽  
pp. 791-794
Author(s):  
Lin Ma
Keyword(s):  
Mechanical Properties ◽  
Moisture Content ◽  
Plane Strain ◽  
Confining Pressure ◽  
Test Method ◽  
The Other ◽  
Strain Condition ◽  
Plane Strain Problem ◽  
Plain Strain ◽  
The Impact

Plane strain problem is currently prevalent in the loess engineering. However, this problem still using conventional triaxial test method for processing. So the paper conducted the plain strain test, analyze differences in plane strain experiments with conventional triaxial experiments under different moisture content and confining pressure. Research shows two points, the first one is the impact on the strength of the soil is more under moisture content than confining pressure, the other is that the soil strength under the plane strain condition is significantly greater than conventional triaxial conditions. It shows that the results were conservative under the plane strain problem at past. It played a certain role in guiding the engineering.

Research on Bursting Liability and its Preventive Measures of -906m Deep Coal and Rock in Zhuji Coal Mine

2012 ◽  
Vol 170-173 ◽  
pp. 428-433 ◽  
Author(s):  
Dong Ming Guo ◽  
Hua Jun Xue ◽  
Li Juan Li ◽  
Jun Long Xue ◽  
Gui He Li
Keyword(s):  
Coal Seam ◽  
Coal Mine ◽  
Water Injection ◽  
Elastic Strain Energy ◽  
Hole Drilling ◽  
Energy Index ◽  
Deep Mining ◽  
Hole Drilling Method ◽  
Drilling Method ◽  
The Impact

Rock burst is a common mine dynamic phenomenon in the world, and the research on bursting liability of coal and rock is the foundation of rock burst’s prevention and treatment. This paper has a research on bursting liability of coal and rock of 11-2 coal seam which is the main coal seam of Zhuji coal mine, and through the research and analysis of coal seam burst energy index(bursting energy index, elastic strain energy index, duration of dynamic fracture) and rock seam burst energy index(bending energy index), this paper given that seam and rock in deep mining section of Zhuji coal mine has bursting liability, put forward a series of countermeasures such as the previous water injection, hole-drilling method, blasting distressing to the coal seam with the impact disaster for deep mining in Zhuji coal mine.

Fabrication and Preliminary Study of a Prototype Bi-Layered Small Diameter Vascular Prosthesis Composed of Nano-Fiber and Silk Fiber

2013 ◽  
Vol 843 ◽  
pp. 66-69 ◽  
Author(s):  
Hui Jing Zhao ◽  
Guo Li Zhou ◽  
Zhi Qing Yuan
Keyword(s):  
Mechanical Properties ◽  
Blood Vessels ◽  
Outer Layer ◽  
Small Diameter ◽  
Peak Stress ◽  
Silk Fiber ◽  
Content Increase ◽  
Peak Strain ◽  
Tissue Engineering Scaffolds ◽  
Vascular Prostheses

Biomaterials used for vascular prostheses should possess certain strength that can keep the normal blood fluidity, as well as certain flexibility and elasticity that can resist blood pulsation pressure. In order to fabricate small diameter vascular prostheses (SDVP) that possess matchable mechanical properties with natural blood vessels, a bi-layered tubular structure composed of electrospinning blended nanofiber and silk fiber was designed and prepared in this study. The inner layer of the structure, prepared through electrospinning, was composed of Poly (L-lactide-co-ε-caprolactone) (PLCL) and silk fibroin (SF) blended nanofibers. Braided silk tube was used as the outer layer of the structure. Morphological, structural and mechanical properties including peak stress, peak strain, and Youngs modulus of the prototype bi-layered SDVP were characterized initially. Results showed that the diameter range of the blended nanofiber was between 100 and 900 nm, and the fiber diameter increased with the content increase of PLCL. Through blending PLCL together with SF, peak stress and peak strain of the electrospun inner layer were improved, and that of the Youngs modulus decreased. Meanwhile, the outer layer of SDVP was stronger and had higher Youngs modulus. Those mechanical performances of the prototype bi-layered SDVP fabricated in this study are similar to natural blood vessels, which provide a promising biomaterial that could be applied on tubular tissue engineering scaffolds.

scholarly journals Numerical Investigation of Influences of Drilling Arrangements on the Mechanical Behavior and Energy Evolution of Coal Models

2018 ◽  
Vol 2018 ◽  
pp. 1-12 ◽  
Author(s):  
Tong-bin Zhao ◽  
Wei-yao Guo ◽  
Feng-hai Yu ◽  
Yun-liang Tan ◽  
Bin Huang ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Energy Dissipation ◽  
Mechanical Behavior ◽  
Rock Burst ◽  
Test Results ◽  
Energy Index ◽  
Energy Evolution ◽  
Compression Tests ◽  
Influencing Mechanism ◽  
Drilling Method

Destress drilling method is one of the commonly used methods for mitigating rock bursts, especially in coal mining. To better understand the influences of drilling arrangements on the destress effect is beneficial for rock burst mitigation. This study first introduced the rock burst mitigation mechanism of the destress drilling method and then numerically investigated the influences of drilling arrangements on the mechanical properties of coal models through uniaxial compression tests. Based on the test results, the energy evolution (i.e., the energy dissipation and bursting energy indexes) influenced by different drilling arrangements was analyzed. When the drilling diameter, the number of drilling holes in one row, or the number of drilling rows increases, the bearing capacity of specimens nonlinearly decreases, but the energy dissipation index increases. In addition, the drilling diameter or the number of drilling holes in one row affects the failure mode weakly, which is different from that of the number of drilling rows. Consequently, the bursting energy index decreases as increasing the drilling diameter or the number of drilling holes in one row, but as increasing the number of drilling rows, the variation law of bursting energy index is not obvious. At last, the influencing mechanism of drilling arrangement on the rock burst prevention mechanism of the destress drilling method was discussed and revealed.

Numerical Simulation of the Effect of Temperature on the Failure Strength of Rock

2013 ◽  
Vol 690-693 ◽  
pp. 1737-1740
Author(s):  
Lin Bu ◽  
Tao Xu ◽  
Yun Jie Zhang
Keyword(s):  
Mechanical Properties ◽  
Rock Fracture ◽  
Strain Curve ◽  
Peak Stress ◽  
Effect Of Temperature ◽  
Peak Strain ◽  
Failure Strength ◽  
Stress Strain Curve ◽  
Physical Tests ◽  
Compression Condition

The mechanical properties of granite experiencing high temperatures under uniaxial compression condition were simulated in this paper. Numerically simulated stress-strain curve, peak stress, peak strain and the tangent elastic modulus were compared with the corresponding physical tests. Simulated results agree well with physical tests results, it is shown that Abaqus is suitable for the analysis of the temperature effect on rock fracture.

scholarly journals Influence of Cyclic Impact Loading and Axial Stress on Dynamic Mechanical Properties of Burst-Prone Coal

2021 ◽  
Vol 2021 ◽  
pp. 1-10 ◽  
Author(s):  
Shuang Gong ◽  
Zhen Wang ◽  
Lei Zhou ◽  
Wen Wang
Keyword(s):  
Mechanical Properties ◽  
Impact Loading ◽  
Coal Sample ◽  
Impact Load ◽  
Axial Stress ◽  
Dynamic Mechanical Properties ◽  
Dynamic Mechanical ◽  
Cyclic Impact Loading ◽  
Cyclic Impact ◽  
The Impact

High in-situ stress and frequent dynamic disturbances caused by the mining process in deep coal mines can easily induce dynamic disasters such as coal burst. We conducted laboratory experiments to assess the effects of the axial stress loading and dynamic cyclic impact loading on the dynamic mechanical properties of burst-prone coals by using a modified split Hopkinson pressure bar (SHPB). Comparisons were made using two types of burst-prone and burst-resistant coal samples. The mineral components, organic macerals, and dynamic mechanical features of both burst-prone and burst-resistant coal samples were comparatively analyzed based on the obtained X-ray diffraction (XRD), optical microscope observations, and dynamic compressive stress-strain curves, respectively. The results of the microstructure analysis indicated a larger difference between the minimum and maximum reflectances of vitrinite for burst-prone coal. Compared to the burst-resistant coal samples, the burst-prone coals contained less corpocollinite and fusinite. While applying a high axial static load combined with cyclic impact load, the coal samples showed the characteristics of fatigue damage. The results also demonstrated that preaxial stress affected the burst resistance of coal samples. The greater the preaxial stress was, the less the coal samples could withstand the dynamic cyclic impact load. In comparison to the burst-resistant coal sample, the burst-prone coal sample showed a larger dynamic compressive strength and a lower deformation. They were also more positively capable of the propagation and activation of the coal burst. We believe that the results of the study are conducive to further understanding of the distribution of microcomponents of burst-prone coals. The results are also beneficial for realizing the dynamic mechanical characteristics of burst-prone coals under the impact of cyclic dynamic load.

scholarly journals SHPB Testing and Analysis of Bedded Shale under Active Confining Pressure

2020 ◽  
Vol 2020 ◽  
pp. 1-8
Author(s):  
Guoliang Yang ◽  
Jingjiu Bi ◽  
Xuguang Li ◽  
Jie Liu ◽  
Yanjie Feng
Keyword(s):  
Mechanical Properties ◽  
Elastic Modulus ◽  
Strain Rate ◽  
Peak Stress ◽  
Confining Pressure ◽  
Dynamic Mechanical Properties ◽  
Dynamic Elastic Modulus ◽  
Peak Strain ◽  
Dynamic Mechanical ◽  
Bedding Angle

Shale gas is the most important new energy source in the field of energy, and its exploitation is very important. The research on the dynamic mechanical properties of shale is the premise of exploitation. To study the dynamic mechanical properties of shale from the Changning-Weiyuan area of Sichuan Province, China, under confining pressure, we used a split Hopkinson pressure bar (SHPB) test system with an active containment device to carry out dynamic compression tests on shale with different bedding angles. (1) With active confining pressure, the shale experiences a high strain rate, and its stress-strain curve exhibits obvious plastic deformation. (2) For the same impact pressure, the peak stress of shale describes a U-shaped curve with an increasing bedding angle; besides, the peak stress of shale with different bedding angles increases linearly with rising confining pressure. The strain rate shows a significant confining pressure enhancement effect. With active confining pressure, the peak strain gradually decreases as the bedding angle increases. (3) As a result of the influence of different bedding angles, the dynamic elastic modulus of shale has obvious anisotropic characteristics. Shale with different bedding angles exhibits different rates of increase in the dynamic elastic modulus with rising confining pressure, which may be related to differences in the development of planes of weakness in the shale. The results of this study improve our understanding of the behavior of bedded shale under stress.

Deep Mining Optimization of Rock Burst Mines

2013 ◽  
Vol 448-453 ◽  
pp. 3859-3862
Author(s):  
Yong Mei
Keyword(s):  
Mechanical Properties ◽  
High Pressure ◽  
Rock Burst ◽  
Water Injection ◽  
Coal Face ◽  
Deep Mining ◽  
Organization Model ◽  
Pressure Water ◽  
Injection Effect ◽  
System Layout

To prevent threaten of impact disaster, high-pressure water is injected into coal face, which is most widely used in impact-type mine. In such cases, by analyzing the rock burst tendency of a particular type of deep mining pit and occurrence of the mining process, rock samples drilled from the coal mine were taken for the conventional mechanical properties test and rock burst tendency test respectively under dry and wet state. Cuttings volume indicator affected by injection has been optimized to improve the prediction sensitivity. "One shift anti-impact, two-shift production "patterns labor organization model, adjusted development system layout and cut drilling index optimizations, as well as the allocation of high-pressure water injection drilling means, greatly improving the water injection effect, which probably provide a reference for similar mines to safe and efficiently mining.

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