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  • Sun, Zhongguang  (5)
  • 1
    Online Resource
    Online Resource
    Study on Deterioration Effect of Dynamic Mechanical Properties of Granite at Subzero Temperatures
    Hindawi Limited ; 2022
    In:  Geofluids Vol. 2022 ( 2022-6-28), p. 1-11
    Details
    In: Geofluids, Hindawi Limited, Vol. 2022 ( 2022-6-28), p. 1-11
    Abstract: In the present work, through the dynamic impact test of frozen granite, the effect of temperature on the dynamic mechanical performances of granite at high strain rates were investigated. Based on the existing energy and damage theory, the effects of different low temperatures on the energy dissipation, damage variables, and strength of red sandstone are explored. The reasons for the deterioration of granite dynamic mechanical strength at low temperature are studied by combining analyses of fracture morphology. Researched results showed that low temperatures ( 〈 -20°C) cause “frostbite” in granite, leading to the sharp decrease of dynamic and macromechanical strength of the rock under a high strain. Under this dynamic disturbance, transient engineering disasters are easy to occur. The analysis of fracture morphology showed that the lower negative temperature results in the formation of cracks among the mineral particles in the granite. Under high strain rate loading, these cracks have poor plastic deformation ability and are easily destabilized and expanded. Moreover, frozen granite tends to be brittle as a whole. With the decrease of negative temperature, its fracture behavior gradually changes from cleavage fracture to transgranular fracture, and the failure mode also changes from tensile failure to shear failure. The coupling effect of impact and the lower negative temperature will cause the quasicleavage of some crystalline minerals, eventually leading to low-stress brittle failure of granite.
    Type of Medium: Online Resource
    ISSN: 1468-8123 , 1468-8115
    URL: Article
    DOI: 10.1155/2022/3899268
    Language: English
    Publisher: Hindawi Limited
    Publication Date: 2022
    detail.hit.zdb_id: 2045012-6
    SSG: 13
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  • 2
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    Online Resource
    Study on the Effect of Negative Temperature Change on the Fracture Morphology of Granite under Impact
    Hindawi Limited ; 2022
    In:  Geofluids Vol. 2022 ( 2022-5-12), p. 1-13
    Details
    In: Geofluids, Hindawi Limited, Vol. 2022 ( 2022-5-12), p. 1-13
    Abstract: SHPB test system was used to conduct dynamic impact experiments on frozen granite under different negative temperatures. The fracture surface of granite under impact load was found via scanning electron microscope (SEM). The micromorphological characteristics of rock fracture under negative temperature are analyzed to explore the influence of negative temperature on the rock fracture morphology, and a practicable explanation is given for the mechanical property changes of rock under different temperatures. Research results showed that low temperatures ( 〈 -20°C) caused “frostbite” in granite, leading to a sharp decrease in the rock dynamic mechanical strength under a high strain. Fracture morphology analysis indicated that the lower negative temperatures resulted in the formation of cracks among the mineral particles in the granite. These cracks have poor plastic deformation ability and are easy to destabilize and expand under a high strain rate. Moreover, the coupling effect of impact and negative temperature will cause the cleavage of some crystalline minerals, eventually resulting in the low-stress brittle failure of granite. It is considered that the nucleation of cracks in negative temperature rock under impact load is mainly caused by crystal deformation, which can be divided into three types: the nucleation of cracks resulted from elastic incompatibility between the grains, the nucleation of cracks caused by interface slip, and the nucleation of cracks caused by plastic deformation in crystalline solid.
    Type of Medium: Online Resource
    ISSN: 1468-8123 , 1468-8115
    URL: Article
    DOI: 10.1155/2022/4918680
    Language: English
    Publisher: Hindawi Limited
    Publication Date: 2022
    detail.hit.zdb_id: 2045012-6
    SSG: 13
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  • 3
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    Application of GPR Underground Pipeline Detection Technology in Urban Complex Geological Environments
    Hindawi Limited ; 2022
    In:  Geofluids Vol. 2022 ( 2022-5-20), p. 1-9
    Details
    In: Geofluids, Hindawi Limited, Vol. 2022 ( 2022-5-20), p. 1-9
    Abstract: In the process of the continuous construction of underground pipelines, underground pipe network systems have become increasingly complex, which puts forward higher requirements for normal operation and maintenance. To address different kinds of complex conditions, this experiment in the present paper takes ground penetrating radar as the research basis and uses a self-correction and screening algorithm to innovatively detect underground pipelines. The results show that urban underground pipeline detection technology based on ground penetrating radar (GPR) can obtain a highly reliable number of pipelines and track predefined pipelines when detecting different numbers of verification pipelines. When detecting underground pipelines in different sections, the vertical and horizontal errors are no more than 0.199 m and 0.248 m, respectively, which means that the detection technology of urban underground pipelines based on GPR has high detection accuracy and can be performed on high-level detection tasks under various complex conditions. This research applies bottom detection radar to urban underground pipeline detection technology under complex conditions for the first time, innovatively uses the action mechanism of bottom detection radar, integrates its high precision and high efficiency into underground pipeline detection technology, and ensures the effectiveness of the detection work.
    Type of Medium: Online Resource
    ISSN: 1468-8123 , 1468-8115
    URL: Article
    DOI: 10.1155/2022/7465919
    Language: English
    Publisher: Hindawi Limited
    Publication Date: 2022
    detail.hit.zdb_id: 2045012-6
    SSG: 13
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  • 4
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    Online Resource
    Mechanical response characteristics and permeability evolution of coal samples under cyclic loading
    Wiley ; 2019
    In:  Energy Science & Engineering Vol. 7, No. 5 ( 2019-10), p. 1588-1604
    Details
    In: Energy Science & Engineering, Wiley, Vol. 7, No. 5 ( 2019-10), p. 1588-1604
    Abstract: Understanding the stress‐cracks‐permeability evolution law inside coal body under cyclic loading is significant to optimize the gas extraction technology and gas disasters prevention technology. In order to explore the influence of mining cyclic stress on the mechanical behavior and permeability variation of gas‐bearing seams, the experiments on permeability evolution, deformation law, and acoustic emission ( AE ) characteristics of coal samples under cyclic loading with different loading stress level and different loading frequency were carried out. These results indicate that the higher loading stress level, the shorter the fatigue life of coal sample. With the increase of the loading stress level, the change rate of permeability became higher and the relation curves between permeability and loading cycles developed from “U” to “V,” which can be defined and divided into three stages, for example, decrease stage, stable stage, and increase stage. And the permeability in the decrease stage can be modeled as a power function of the loading cycles, while the permeability in the increase stage can be modeled as an exponential function of the loading cycles. Besides, the loading stress level has a significant on the permeability, while the loading frequency has little impact on the permeability evolution. In the process of coal deformation under cyclic loading, the strain development of strain coal samples was in the shape of inverted “S,” while the variation of the peak values of corresponding AE ring counts presented “U” type. In addition, there was a good correlation between the permeability and the AE parameters of coal samples, which provide a new sight into the dynamic variation process of the stress‐cracks‐permeability evolution inside coal body under cyclic loading.
    Type of Medium: Online Resource
    ISSN: 2050-0505 , 2050-0505
    URL: Issue
    URL: Article
    DOI: 10.1002/ese3.v7.5
    DOI: 10.1002/ese3.368
    Language: English
    Publisher: Wiley
    Publication Date: 2019
    detail.hit.zdb_id: 2720339-6
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  • 5
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    Study on Roof-Coal Caving Characteristics with Complicated Structure by Fully Mechanized Caving Mining
    Hindawi Limited ; 2019
    In:  Shock and Vibration Vol. 2019 ( 2019-04-18), p. 1-20
    Details
    In: Shock and Vibration, Hindawi Limited, Vol. 2019 ( 2019-04-18), p. 1-20
    Abstract: With mining technology and mechanization degree being improving, fully mechanized caving mining technology (FCM) has become a main method for thick coal seam extraction in China. However, roof-coal caving characteristics in turn restrict its recovery efficiency, especially for the coal seam with complicated structure (CCS), that is, the coal seam comprises hard or soft coal and gangue. In order to explore the key factors influencing the roof-coal caving and recovery characteristics, related research work has been conducted as follows: firstly, a mechanical model of CCS has been established, which indicates the strength of the coal and gangue will directly affect the roof-coal recovery. Meanwhile, based on the geological settings of Qinyuan coal mine, numerical simulation on roof-coal caving law under different thicknesses of hard or soft coal and gangue has been performed using UDEC software. The results show that the maximum principal stress will increase with the increase of mining depth, making the roof-coal to break easily. Furthermore, the range of the plastic zone of the top coal and the damage degree of the top coal increase with the increase of mining depth. Physical modeling results show that when an extraction-caving ratio is 1, the number of times the coal arch forms is 0.43 at every caving, up to a maximum of 3; the number of times coal arch forms with an extraction-caving ratio of 2 is 4.65 times larger than that with an extraction-caving ratio of 1. The probability of coal arch formation with an extraction-caving ratio of 3 is minimal, about 0.4, which is due to that the arch span is large and the curvature is small, so it is difficult to form a stable arch structure. According to the mechanical characteristics of roof-coal in Qinyuan coal mine, deep-hole blasting technique has been used to reduce the fragments of roof-coal crushed. The results show that this technique can effectively improve the recovery of roof-coal.
    Type of Medium: Online Resource
    ISSN: 1070-9622 , 1875-9203
    URL: Article
    DOI: 10.1155/2019/6519213
    Language: English
    Publisher: Hindawi Limited
    Publication Date: 2019
    detail.hit.zdb_id: 2070162-7
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