湿干冻融耦合循环作用下硫酸盐渍土力学特性劣化规律研究

    Study on deterioration patterns of mechanical properties of sulfate saline soil under coupled wet-dry and freeze-thaw cycles

    • 摘要: 为揭示硫酸盐渍土在湿干冻融耦合循环下的力学特性劣化规律与内在损伤机制,本文以不同硫酸钠含量的重塑盐渍土试样为对象,开展了不同循环次数下的湿干冻融耦合循环试验及三轴剪切试验研究。结果表明:损伤状态下,含盐量对强度具有显著抑制作用,试样强度的衰减由黏聚力单调劣化所主导。而随着循环次数的增加,依据含盐量的有无,试样呈现出两种截然不同的强度衰减模式。无盐试样表现为黏聚力单调劣化、内摩擦角增大的准单调衰减模式;而含盐试样则表现出独特的W形振荡劣化模式,其峰值应力和黏聚力在N = 6和N = 15时出现显著恢复,内摩擦角表现为复杂的非同步波动。同时,高围压条件能够有效抑制循环损伤导致的向理想塑性模式的转变。盐分在湿干冻融耦合循环中表现为损伤与恢复双重效应,其主导的损伤-恢复动态反馈循环是导致上述复杂演化模式的根本原因。

       

      Abstract: To reveal the deterioration patterns of mechanical properties and intrinsic damage mechanisms of sulfate saline soil under coupled wet-dry and freeze-thaw cycles, remolded saline soil specimens with varying sodium sulfate contents are prepared. Coupled wet-dry and freeze-thaw cycle tests with varying numbers of cycles and triaxial shear tests are then conducted. The research results show that under damaged conditions, the salt content has a significant inhibitory effect on the strength, and the attenuation of the specimen strength is dominated by the monotonic deterioration of cohesion. With the increase in the number of cycles, depending on the presence or absence of salt content, the specimens exhibit two distinctly different strength attenuation modes. Salt-free specimens exhibit a quasi-monotonic attenuation mode characterized by monotonic deterioration of cohesion and an increase in the internal friction angle; in contrast, salt-containing specimens show a unique W-shaped oscillatory deterioration mode, where their peak stress and cohesion undergo significant recovery at N = 6 and N = 15, while the internal friction angle presents complex non-synchronous fluctuations. Meanwhile, high confining pressure conditions can effectively inhibit the transformation to a perfectly plastic mode caused by cyclic damage. Salt exhibits dual effects of damage and recovery during coupled wet-dry and freeze-thaw cycles. The salt-dominated damage-recovery dynamic feedback mechanism is identified as the root cause of the aforementioned complex evolutionary patterns.

       

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