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- 저자 : Yingren Zheng (검색결과 3 건)
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Yu Cong,Heyi Liu,Liming Zhang,Sai Li,Yingren Zheng,Zaiquan Wang,Erdi Abi 대한토목학회 2021 KSCE JOURNAL OF CIVIL ENGINEERING Vol.25 No.11
A similarity model with a volumetric similarity ratio of 1:100 and a granular flow model for the tunnel were designed. By comparing macroscopic and mesoscopic information (such as fracture process, strain evolution, stress transfer, crack propagation, and stress distribution) of the tunnel models under load, the failure mechanism of the metro tunnel under load was investigated. The result showed that: 1) under the loading path, the instability area of the tunnel is mainly distributed in the straight wall on both sides. When the load is 1.5 MPa, a large number of cracks on both sides of the straight wall run through, resulting in the initial failure of the rock mass; 2) the surface rock mass of arch bottom is under tensile stress and the deep rock mass is under pressure stress, therefore, the fracture does not develop continuously. The surface of straight wall produces continuous development crack under the action of tensile stress; 3) the arch bottom first responds during the stress redistribution of the small-span tunnel; the top and middle parts of the side walls of the running tunnel with greatest potential for damage respond most; 4) in the process of stress redistribution, the peak stress of the deep measuring points of the straight wall is greater than that of the free surface; 5) at the initial stage of loading, tensile cracks account for a high proportion of all cracks found. When the load is 1.5 MPa, the proportion of shear cracks increases to 28%, and when the load is 1.6 Mpa, the proportion of shear cracks increases to 31%. Finally, the tensile-shear effect triggers the failure of the tunnel.
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Nonexistence and non-decoupling of the dissipative potential for geo-materials
Liu, Yuanxue,Zhang, Yu,Wu, Runze,Zhou, Jiawu,Zheng, Yingren Techno-Press 2015 Geomechanics & engineering Vol.9 No.4
Two fundamental issues exist in the damage theory of geo-material based on the concept of thermodynamics: existence or nonexistence of the dissipation potential, and whether the dissipation potential could be decoupled into a damage potential and a plastic one or not. Thermodynamics theory of elastoplastic damage assumes the existence of dissipation potential, but the presence of dissipation potential is conditional. Based on the dissipation inequality in accord with the second law of thermodynamics, the sufficient and necessary conditions are given for the existence of the dissipation potential separately in total and incremental forms firstly, and proved strictly in theory. With taking advantage of the basic mechanical properties of geo-materials, the nonexistence of the dissipative potential is verified. The sufficient and necessary conditions are also given and proved for the decoupling of the dissipation potential of geo-materials in total and incremental forms. Similarly, the non-decoupling of the dissipation potential has also been proved, which indicates the dissipation potential of geo-materials in total or incremental forms could not be decoupled into a dissipative potential for plasticity and that for damage respectively. The research results for the fundamental issues in the thermodynamics theory of damage will help establish and improve the theoretic basis of elastoplastic damage constitutive model for geo-materials.
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Nonexistence and non-decoupling of the dissipative potential for geo-materials
Liu, Yuanxue,Zhang, Yu,Wu, Runze,Zhou, Jiawu,Zheng, Yingren Techno-Press 2015 Geomechanics & engineering Vol.9 No.5
Two fundamental issues exist in the damage theory of geo-material based on the concept of thermodynamics: existence or nonexistence of the dissipation potential, and whether the dissipation potential could be decoupled into a damage potential and a plastic one or not. Thermodynamics theory of elastoplastic damage assumes the existence of dissipation potential, but the presence of dissipation potential is conditional. Based on the dissipation inequality in accord with the second law of thermodynamics, the sufficient and necessary conditions are given for the existence of the dissipation potential separately in total and incremental forms firstly, and proved strictly in theory. With taking advantage of the basic mechanical properties of geo-materials, the nonexistence of the dissipative potential is verified. The sufficient and necessary conditions are also given and proved for the decoupling of the dissipation potential of geo-materials in total and incremental forms. Similarly, the non-decoupling of the dissipation potential has also been proved, which indicates the dissipation potential of geo-materials in total or incremental forms could not be decoupled into a dissipative potential for plasticity and that for damage respectively. The research results for the fundamental issues in the thermodynamics theory of damage will help establish and improve the theoretic basis of elastoplastic damage constitutive model for geo-materials.
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