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Abstract

In the Carboniferous rock mass of the Upper Silesian Coal Basin, large changes in the geomechanical conditions often occur over relatively short distances. These conditions relate to rock properties that are primarily responsible for the occurrence of geodynamic phenomena in the rock mass. The main factor influencing the manifestation of these phenomena is tectonic stress developed during Variscan and subsequent Alpine orogenesis. This stress contributed to creating tectonic structures in the Carboniferous formations and influenced the properties of the rocks themselves and the rock mass they form. As a result of the action of the stresses, compaction zones (main stresses were compressive) were formed, along with zones in which one of the main stresses was tensile. For the compaction zones in the Carboniferous rocks, the following geomechanical parameters have been calculated: uniaxial compressive strength, Young’s modulus and post-critical modulus. The local stress field was determined according to the focal mechanism in selected areas (Main and Bytom troughs) to characterize changes in geomechanical properties of the rocks that are responsible for high-energy tremors (E ≥ 106 J, ML ≥ 2.2).

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Authors and Affiliations

Józef Dubiński
Krystyna Stec
Mirosława Bukowska
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Abstract

Because the heat release of plutonium material, the composite structure is heated and the stress and strain of the composite structure will increase, which will affect the thermodynamic properties of the structure. The thermodynamic analysis of complex structures, which are composed of concentric structures of plutonium, beryllium, tungsten, explosives, and steel, was carried out. The results showed that when the structure is spherical, the temperature is higher than that of the ellipsoid structure. Stress of the elliptical structure is greater than the spherical structure. This study showed that the more flat the shell is, the greater the stress concentration point occurs at the long axis, and the maximum stress occurs at the beryllium layer. These conclusions provide theoretical support for the plutonium composite component testing.

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Authors and Affiliations

Gou Zhenzhi
He Bin
Yang Guilin
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Abstract

As the duration of a rock burst is very short and the roadway is seriously damaged after the disaster, it is difficult to observe its characteristics. In order to obtain the dynamic characteristics of a rock burst, a modified uniaxial compression experiment, combined with a high-speed camera system is carried out and the process of a rock burst caused by a static load is simulated. Some significant results are obtained: 1) The velocity of ejected particles is between 2 m/s and 4 m/s. 2) The ratio of elastic energy to plastic energy is about five. 3) The duration from integrity to failure is between 20 ms and 40 ms. Furthermore, by analyzing the stress field in the sample with a numerical method and crack propagation model, the following conclusions can be made: 1) The kinetic energy of the ejected particles comes from the elastic energy released by itself. 2) The ratio of kinetic energy to elastic energy is between 6% and 15%. This can help understand the source and transfer of energy in a rock burst quantitatively.
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Bibliography

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[2] G . Su Y. Shi, X. Feng, J. Jiang, J. Zhang, Q. Jiang, True-Triaxial Experimental Study of the Evolutionary Features of the Acoustic Emissions and Sounds of Rockburst Processes. Rock Mech. Rock Eng. 51, 375-389 (2018). DOI: 10.1007/ s00603-017-1344-6
[3] F. Gong, Y. Luo, X. Li, X. Si, M. Tao, Experimental simulation investigation on rockburst induced by spalling failure in deep circular tunnels. Tunn. Undergr. Sp. Tech. 81, 413-427(2018). DOI: 10.1016/j.tust.2018.07.035
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Authors and Affiliations

Weiyu Zheng
1 2

  1. China University of Mining & Technology (Beijing), School of Energy and Mining Engineering, China
  2. State Key Laboratory of Coal Mining and Clean Utilization, China
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Abstract

To study the influence of temperature field and stress field on the cracking of the small thickness steel plate concrete composite shear wall (SPCW) in the early stage of construction. The temperature field and stress field of a 400 mm thickness SPCW was monitored and simulated through experimental research and numerical simulation. Moreover, a series of parameter analyses were carried out by using ANSYS to investigate the distribution of temperature field and stress field of SPCW. Based on the analysis results, some suggestions are put forward for controlling the cracking of SPCW in the early stage of construction. The results show that the temperature stress of 400 mm thickness SPCW in the early stage of construction is small, and there is no crack on the wall surface. For SPCW with thickness less than 800mm, the temperature stress caused by hydration heat in the early stage of construction is small, and the wall will not crack. The parameters such as wall thickness, steel plate thickness, boundary condition and stud space significantly influence the temperature field and stress field distribution of the small thickness SPCW in the early stage of construction, and reasonable maintenance measures can avoid cracking.
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Authors and Affiliations

Yun Sun
1
Yaojie Guo
1

  1. Wuhan University, School of Civil Engineering, No.8 of Donghu South Road in Wuhan, Hubei, China
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Abstract

The research on deformation zoning mechanism of tunnel surrounding rock is of great significance for ensuring safe production and disaster prevention in coal mines. However, the traditional deformation zoning theory of tunnel surrounding rock uses the ideal strain softening model as the criterion for judging the zoning type of all tunnel surrounding rock, ignoring the difference between the deformation zoning type of a specific actual tunnel and the basic zoning type of surrounding rock. In order to study the method for determining the actual deformation zoning type of tunnel surrounding rock, the formation mechanism of the actual deformation zoning of tunnel surrounding rock has been revealed. Combined with engineering examples, a method for determining the actual deformation zoning type and boundary stress of specific tunnel surrounding rock has been proposed. The results show that the boundary stress and position of the actual deformation zone are determined by the peak strength fitting line, residual strength fitting line, support strength line, and the position of the circumferential and radial stress relationship lines of each deformation zone. The actual boundary stress of each zone of tunnel surrounding rock is ultimately only related to the basic mechanical properties of the tunnel surrounding rock and the in-situ stress field. The research results can provide reference for disaster management of underground engineering, stability evaluation of surrounding rock, and support scheme design.
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Authors and Affiliations

Wei Jing
1
ORCID: ORCID
Yunlong Gao
2
ORCID: ORCID
Rencai Jin
3
ORCID: ORCID
Laiwang Jing
1
ORCID: ORCID

  1. Anhui University of Science and Technology, State key Laboratory of Mining response and disaster Prevention and Control in Deep Coal Mines, 168 Taifeng Street, Huainan City, Anhui Province, China
  2. Anhui University of Science and Technology, School of Civil Engineering and Architecture, 168 Taifeng Street, Huainan City, Anhui Province, China
  3. China MCC17 Group Co., LTD., Civil Engineering Post-doctoral Research Worktation, No. 88 Yushan East Road, Huashan District, Ma’anshan City, Anhui Province, China

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