ISSN 1000-3665 CN 11-2202/P

    考虑干湿-冻融耦合损伤机制的结构性黄土强度准则

    Strength Criteria for structural Loess considering coupled dry-wet-frost-thaw Damage mechanisms

    • 摘要: 季节性冻土区土体边坡稳定性受自然环境影响明显,而目前对多因素共同作用下的损伤识别与力学响应方面研究有限。通过开展干湿-冻融耦合下的不同循环次数的固结排水三轴剪切试验及核磁、电镜扫描试验,从宏-细观角度分析结构性黄土的力学特性变化规律及损伤劣化机制,将微观颗粒孔隙变化同强度参数进行关联性分析。最终建立干湿-冻融耦合下结构性黄土的强度准则,并验证其合理性。结果表明:应力-应变曲线的软/硬化特征与循环次数及围压大小有关,伴随循环次数及围压的增加,应力应变曲线逐渐由软化过渡到硬化特征,在循环作用下,强度参数黏聚力较内摩擦角损伤更多,其劣化率更高。10次循环后孔隙面积增加40%左右,胶结块的受损使得孔隙面积逐渐增大,微、小孔隙转变为大、中孔隙,土体内部形成新的分布形态,孔隙细观孔隙增加规律同宏观强度参数的劣化规律一致。干湿-冻融循环后,在剪切作用中,土体内部胶结元逐渐向摩擦元转换,土体提供强度部分演化情况为胶结块-胶结块和软弱带-软弱带,形成新的强度承担机制。为季冻区边坡稳定性评价及防护提供理论借鉴。

       

      Abstract: The stability of soil slopes in seasonal frozen soil areas is significantly affected by the natural environment. However, at present, there are limited studies on damage identification and mechanical responses under the combined action of multiple factors. By conducting triaxial shear tests (CD) of consolidated drainage with different cycle numbers under the coupling of dry-wet and freeze-thaw, as well as nuclear magnetic resonance and electron microscope scanning tests, the variation laws of mechanical properties and damage and deterioration mechanisms of structural loess were analyzed from a macro-mesoscopic perspective, and the correlation analysis between the pore changes of microscopic particles and strength parameters was carried out. Finally, the strength criterion of structural loess under the coupling of dry-wet and freeze-thaw was established and,its rationality was verified. The results show that the soft/hardening characteristics of the stress-strain curve are related to the number of cycles and the magnitude of confining pressure. With the increase of cycles numbers and confining pressure, the stress-strain curve gradually transitions from softening to hardening characteristics. Under the action of cycles, the strength parameter cohesive force is more damaged than the internal friction Angle, and its deterioration rate is higher. After 10 cycles, the pore area increased by about 40%. The damage of the cementation blocks led to a gradual increase in the pore area. Micro-small pores transformed into large-medium pores, and a new distribution pattern was formed within the soil. The increase law of the mesoscale pores was consistent with the deterioration law of the macroscopic strength parameters. After the dry-wet-freeze-thaw cycle, during the shear action, the cementing elements inside the soil gradually transform into friction elements. The evolution of the part of the soil providing strength is cementing block-cementing block and weak zone - weak zone, forming a new strength-bearing mechanism. This research provides theoretical reference for the stability evaluation and protection of slopes in seasonally frozen areas.

       

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