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  • 1
    Online Resource
    Online Resource
    Study on Shear Mechanical Properties and Fracture Evolution Mechanism of Irregular Serrated Rock Discontinuities
    MDPI AG ; 2023
    In:  Applied Sciences Vol. 13, No. 4 ( 2023-02-14), p. 2444-
    Details
    In: Applied Sciences, MDPI AG, Vol. 13, No. 4 ( 2023-02-14), p. 2444-
    Abstract: To analyze the shear characteristics and mesoscopic failure mechanism of irregular serrated rock discontinuities, a great deal of interview samples of irregular serrated structures were made by 3D printing technology, and laboratory shear tests were carried out on them under different normal stresses. At the same time, PFC numerical simulation software is used to establish relevant models to study the evolution of microcracks and the distribution characteristics of the force chain on the rock discontinuity during the shear process. The results show that the shear mechanical properties of irregular serrated rock discontinuities are affected by normal stress, undulating angle, and undulating height. The shear strength increases with the increase of normal stress and undulating height, and decreases with the increase of undulating angle. The numerical simulation results show that the irregular structural surface cracks under different undulation angles, which first start at the near force end serration root on both sides and further evolve to the adjacent serrations, while the irregular structural surface cracks under different undulation heights, which first start at the serration root with the lowest height and expand to the adjacent serrations. At the same time, the number of cracks increases with the increase of normal stress and the force chain is mainly distributed near the sawtooth surface. The force chain is more concentrated near the near force end sawtooth and at the tip and root of the rest of the sawtooth. At the same time, the direction of the force chain is approximately perpendicular to the force surface of the sawtooth. The research results are helpful in further understanding the shear mechanical properties and differences of irregular serrated rock discontinuities.
    Type of Medium: Online Resource
    ISSN: 2076-3417
    URL: Article
    DOI: 10.3390/app13042444
    Language: English
    Publisher: MDPI AG
    Publication Date: 2023
    detail.hit.zdb_id: 2704225-X
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  • 2
    Online Resource
    Online Resource
    Study on Shear Behavior and Failure Characteristics of Bolted Anisotropic Rock Joints
    MDPI AG ; 2023
    In:  Materials Vol. 16, No. 6 ( 2023-03-09), p. 2210-
    Details
    In: Materials, MDPI AG, Vol. 16, No. 6 ( 2023-03-09), p. 2210-
    Abstract: Anisotropic discontinuity exists widely in rock masses of mines, tunnels, slopes, water conservancy and hydropower projects. The shear characteristics of bolted anisotropic rock joints are extremely important for the stability design of engineering rock mass. However, few scholars have studied the bolted anisotropic rock joint. The different rock properties on both sides of the rock joint, especially the different rock strengths, will greatly affect the deformation characteristics and failure mode of the rock mass. Based on this, a series of shear tests were carried out on the bolted anisotropic rock joint under different normal stresses, and the characteristics of shear stress–shear displacement curve, shear strength, failure characteristics of the rock joint and deformation characteristics of the bolt are discussed. λ is defined as the strength ratio of upper and lower rock on the structural surface. The results show that the effect of λ on the shear stress–shear displacement curve is not obvious at the pre-fracture stage. The shear stress–shear displacement curve at the pre-breaking stage of the bolt presents a softening stage when the normal stress is equal to 0.5 MPa, tends to be horizontal when the normal stress is equal to 1 MPa and presents a hardening stage when the normal stress is greater than 1 MPa. After the bolt is broken, the shear stress–shear displacement curve presents a stepped-down descent. With the increase in λ, the breaking shear stress of the bolt increases. Elliptic failure occurs on the surface of the bolted anisotropic rock joint, and the length of the major axis of the ellipse decreases with the increase in λ value and normal stress. The bolts with different λ values of anisotropic rock joint show “Z-shaped” tensile bending deformation characteristics after shear fracture, and the horizontal and vertical components of the bolt deformation decrease with the increase in λ value and normal stress. The fracture shear displacement of the bolt increases with the increase in normal stress and decreases with the increase in λ value. The research results are helpful to further understand the shear mechanical characteristics and differences of bolted rock joints and provide a reference for solving the engineering problems of the composite layered rock mass.
    Type of Medium: Online Resource
    ISSN: 1996-1944
    URL: Article
    DOI: 10.3390/ma16062210
    Language: English
    Publisher: MDPI AG
    Publication Date: 2023
    detail.hit.zdb_id: 2487261-1
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  • 3
    Online Resource
    Online Resource
    Bearing Characteristics of Rock Joints under Different Bolts Installation Angles and Their Underlying Mechanism
    MDPI AG ; 2023
    In:  Sustainability Vol. 15, No. 17 ( 2023-08-25), p. 12876-
    Details
    In: Sustainability, MDPI AG, Vol. 15, No. 17 ( 2023-08-25), p. 12876-
    Abstract: To explore the mechanical failure characteristics of bolted joints under different bolt installation angles and the effect of bolting on the shear strength of joints, a numerical model of structural plane anchoring with different bolt installation angles was established based on the improved Pile element, and a series of uniaxial compression numerical tests were carried out to systematically study the effects of bolt installation angle on bolts. The results show that as the bolt installation angle increases, the peak stress of the specimen is first constant and then decreases, and the elastic modulus of the specimen decreases nonlinearly. When the bolt installation angle is lower than 45°, the bearing capacity of the joints is higher. The interaction between the bolt and the specimen’s force is mainly concentrated at the intersection of the structural plane and the area where the nut gaskets are installed at both ends of the bolt. The horizontal stress is higher in the area where the nut gaskets are installed at both ends of the bolt. With an increase in bolt installation angle, the plastic zone volume of the anchored joint specimen increases linearly with an exponential function. When the bolt installation angle is lower than 45°, the plastic zone volume increases slowly, and when the bolt installation angle is higher than 45°, the plastic zone volume increases rapidly. When the bolt installation angle is small, the contribution of the bolt axial force is greater than that of the bolt shear force. In contrast, when the bolt installation angle is large, the contribution of the bolt axial force is lower than the contribution of the bolt shear force. With an increase in bolt installation angle, the contribution of the bolt axial force decreases nonlinearly, the contribution of the bolt shear force increases linearly, and the shear resistance decreases nonlinearly. The optimal bolt installation angle is about 45°, but the optimal bolt installation angle also changes constantly under the influence of factors such as bolt type, rock strength, and external load.
    Type of Medium: Online Resource
    ISSN: 2071-1050
    URL: Article
    DOI: 10.3390/su151712876
    Language: English
    Publisher: MDPI AG
    Publication Date: 2023
    detail.hit.zdb_id: 2518383-7
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  • 4
    Online Resource
    Online Resource
    Broadband Achromatic Quarter-Waveplate Using 2D Hybrid Copper Halide Single Crystals
    American Chemical Society (ACS) ; 2023
    In:  Journal of the American Chemical Society Vol. 145, No. 32 ( 2023-08-16), p. 18007-18014
    Details
    In: Journal of the American Chemical Society, American Chemical Society (ACS), Vol. 145, No. 32 ( 2023-08-16), p. 18007-18014
    Type of Medium: Online Resource
    ISSN: 0002-7863 , 1520-5126
    URL: Article
    URL: Article
    DOI: 10.1021/jacs.3c05705
    DOI: 10.1021/jacs.3c05705.s001
    RVK:
    VA 1120 ; VA 1752
    Language: English
    Publisher: American Chemical Society (ACS)
    Publication Date: 2023
    detail.hit.zdb_id: 1472210-0
    detail.hit.zdb_id: 3155-0
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  • 5
    Online Resource
    Online Resource
    Research on the Metasurface for Single-Photon Avalanche Photodiode
    Frontiers Media SA ; 2020
    In:  Frontiers in Physics Vol. 8 ( 2020-11-16)
    Details
    In: Frontiers in Physics, Frontiers Media SA, Vol. 8 ( 2020-11-16)
    Type of Medium: Online Resource
    ISSN: 2296-424X
    URL: Article
    DOI: 10.3389/fphy.2020.585871
    Language: Unknown
    Publisher: Frontiers Media SA
    Publication Date: 2020
    detail.hit.zdb_id: 2721033-9
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  • 6
    Online Resource
    Online Resource
    Research on the Mechanism of the Passive Reinforcement of Structural Surface Shear Strength by Bolts under Structural Surface Dislocation
    MDPI AG ; 2022
    In:  Applied Sciences Vol. 13, No. 1 ( 2022-12-30), p. 543-
    Details
    In: Applied Sciences, MDPI AG, Vol. 13, No. 1 ( 2022-12-30), p. 543-
    Abstract: In order to study the local deformation of an anchor bolt and the improvement in the shear strength of a structural surface under the misalignment of an anchorage structure surface, FLAC3D software was used to simulate granite, sandstone, and coal specimens with anchorage angles of 90° to analyze the damage of the anchoring agent and the changes in the local axial and shear forces of the anchor bolts with the misalignment of the structural surface. The results show that the anchor bolt near the structural surface had significant local characteristics with the misalignment of the structural surface; that is, the length of the local deformation area of the bolt was approximately equal to the length of the damaged area of the anchoring agent, and the stress on the anchor bolt was in a coupled tensile–shear stress state when the bolt reached the yield state. For the fully grouted bolts, it was this significant local feature that made the shear strength of the structural surface increase rapidly under a small shear displacement so that the structural surface reached a stable state. The improvement in the shear strength of the anchoring structural surface was caused by the misalignment of the structural surface. This is referred to as the passive improvement of the shear strength of the anchoring structural surface, which is the mechanism of the bonding section anchor to control the shear displacement of the structural surface and realize the stability of the rock mass.
    Type of Medium: Online Resource
    ISSN: 2076-3417
    URL: Article
    DOI: 10.3390/app13010543
    Language: English
    Publisher: MDPI AG
    Publication Date: 2022
    detail.hit.zdb_id: 2704225-X
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  • 7
    Online Resource
    Online Resource
    Decisions should be Taken on the Mainstream Reforms in Cropping Systems
    Informa UK Limited ; 1981
    In:  Chinese Economic Studies Vol. 15, No. 2 ( 1981-12), p. 82-89
    Details
    In: Chinese Economic Studies, Informa UK Limited, Vol. 15, No. 2 ( 1981-12), p. 82-89
    Type of Medium: Online Resource
    ISSN: 0009-4552
    URL: Article
    DOI: 10.2753/CES1097-1475150282
    RVK:
    QA 10000
    Language: English
    Publisher: Informa UK Limited
    Publication Date: 1981
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