The stability of rock masses in large-scale hydropower projects and high-slope excavation engineering is significantly influenced by the unloading of confining pressure. This study investigates the triaxial creep behaviour of limestone under varying conditions of confining pressure unloading through systematic experimental research. Using a ZYSS2000C triaxial shear rheometer, limestone samples from the Qinling region were subjected to a series of triaxial creep tests with controlled unloading conditions. Experimental setups included varying single-step unloading magnitudes of confining pressure (2 MPa, 4 MPa, and 6 MPa) under constant axial stress. The results demonstrated that the magnitude of confining pressure unloading had a pronounced impact on creep behaviour. Larger unloading magnitudes led to shorter total creep durations and reduced cumulative deformation, highlighting the pivotal role of unloading intensity in governing creep characteristics. During the unloading creep process, the deviatoric stress of the rock decreased, and the deformation predominantly manifested as radial dilation. These findings provide new insights into the rock deformation mechanisms induced by confining pressure unloading and offer valuable theoretical and practical guidance for slope excavation and stability management.
The free vibration characteristics of functionally graded porous (FGP) beams were investigated through the application of hyperbolic shear deformation theory (HSDT). The material properties were described using a modified rule of mixtures, incorporating the porosity volume fraction to account for various porosity distribution types, enabling the continuous variation of properties across the beam thickness. The kinematic relations for FGP beams were formulated within the framework of HSDT, and the governing equations of motion were derived using Hamilton’s principle. Analytical solutions for free vibration under simply supported boundary conditions were obtained using Navier’s method. Validation was conducted through comparisons with existing data, demonstrating the accuracy and reliability of the proposed approach. The effects of porosity distribution patterns, power-law indices, span-to-depth ratios, and vibrational mode numbers on the natural frequency values of FGP beams were comprehensively examined. The findings provide critical insights into the influence of porosity and geometric parameters on the dynamic behavior of functionally graded (FG) beams, offering a robust theoretical foundation for their design and optimization in advanced engineering applications.
This study investigates the performance of star-shaped auxetic structures as protective materials in aluminum containers, designed to safeguard sensitive or hazardous materials during road transport. Finite element analysis (FEA) was conducted to assess the impact resistance of the star-shaped auxetic structure under high-speed collisions, simulating potential events such as explosions or sudden impacts. The simulations were performed using Autodesk's event simulation algorithm. In the first analysis, the auxetic structure was subjected to loading conditions applied to the metallic casing, while in the second, the metallic casing was considered rigid, with the focus placed on the structural behavior of the auxetic material under extreme stress conditions. Both scenarios examined the response of the auxetic structure in the plastic deformation region. The results indicate that the maximum stress developed in both loading cases approached 80 MPa. Notably, in the second scenario involving the rigid casing, the maximum displacement of the auxetic structure increased threefold compared to the first study. Despite the extreme loading conditions, the auxetic structure maintained significant cohesion, ultimately failing in a controlled manner. The ability of the star-shaped auxetic structure to absorb substantial impact loads is attributed to the twisting deformation of the structure, which redirects the applied stress towards the center of the impact area. These findings highlight the potential of star-shaped auxetic materials in providing enhanced protection for sensitive materials during transport, demonstrating their ability to withstand severe dynamic loading and to effectively dissipate energy upon impact.
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