冻融-围压作用下含岩桥花岗岩宏细观损伤特征研究

Macro and meso scale damage characteristics of granite with rock bridges under freeze-thaw cycles and confining pressure

  • 摘要: 针对寒区岩体工程中裂隙岩体面临冻融与地应力共同作用下的失稳风险,以含预制岩桥的花岗岩为研究对象,通过开展冻融循环、三轴压缩试验,结合声发射实时监测、矿物组分分析及微观结构观测,系统揭示了冻融与围压共同作用下含岩桥花岗岩的宏细观损伤响应规律。结果表明:①冻融循环作用导致长石等矿物晶格损伤与矿物颗粒边界微裂隙扩展,岩石损伤演化呈现前期快速累积、后期渐趋稳定的阶段性特征。②随着冻融次数增加,应力-应变曲线峰前、峰后出现反复应力降,振铃数出现更早且更加密集、分布趋于分散,表明内部损伤的发展逐渐平缓、非连续,破坏模式由突发性向渐进延性转变。③低裂隙倾角试件在低冻融次数下以裂隙端部张拉破坏为主,岩桥相对完整,随冻融次数增加,破坏转变为岩桥的拉剪贯通破坏;高裂隙倾角试样破坏始终贯通岩桥,随冻融次数增加,破坏发展为菱形剪切破坏。④裂隙倾角主导裂纹萌生位置与扩展方向;围压抑制拉伸破裂,并延缓冻融劣化效应;冻融循环促使破坏形态从单一剪切面演化为复杂的共轭剪切网络。该研究结果可为寒区岩体工程的稳定性评估与灾害防控提供依据。

     

    Abstract: In response to the instability risks faced by fractured rock masses in cold regions under the coupled effects of freeze-thaw cycles and in-situ stress, this study focuses on granite with prefabricated rock bridges. By conducting freeze-thaw cycle tests and triaxial compression experiments, combined with real-time acoustic emission monitoring, mineral composition analysis, and microstructural observation, the macro meso scale damage mechanisms of granite containing rock bridges under the combined action of freeze-thaw and confining pressure are systematically revealed. The results are as follows: ①The freeze-thaw cycles leads to lattice damage of minerals such as feldspar and the propagation of micro-cracks at the boundaries of mineral particles. The evolution of rock damage exhibits a phased characteristic, with rapid accumulation in the initial stage and gradual stabilization in the later stage. ②With the increase of freeze-thaw cycles, the stress-strain curve exhibits repeated stress drops. The ring counts appears earlier and more densely, with a distribution that tends to be more dispersed. This indicates that the development of internal damage gradually slows down and becomes discontinuous, and the failure mode transitions from sudden to gradual ductility. ③For specimens with low fracture inclination angles, tensile failure at the fracture tip is predominant under a low number of freeze-thaw cycles, with the rock bridge remaining relatively intact. As the number of freeze-thaw cycles increases, the failure mode transitions to tensile-shear failure through the rock bridge. For specimens with high fracture inclination angles, the failure always penetrates through the rock bridge, and as the number of freeze-thaw cycles increases, the failure progresses to rhombic shear failure. ④The fracture inclination angle dominates the propagation direction of cracks. Confining pressure inhibits tensile fracture and delays the freeze-thaw deterioration effect. Freeze-thaw cycles promote the evolution of failure modes from a single shear plane to a complex conjugate shear network, significantly increasing the degree of fragmentation. These findings can provide a basis for stability assessment and disaster prevention for rock engineering in cold regions.

     

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