摘要: |
为探究季冻区恶劣气候对不同含水率下渠基膨胀土的胀缩变形和物理力学性质带来的影响,以北疆阿勒泰地区膨胀土为研究对象,室内模拟北疆地区实际冻融变化的气候条件的冻融循环试验,基于此,对含水率为12%,16%,20%的膨胀土进行体积变形试验、无侧限抗压强度试验和SEM电镜扫描试验,着重分析了冻融循环作用对膨胀土体积变形和力学特性的影响规律。结果表明:冻融循环作用过程中,随含水率的增加,试样的体积变形由“冻缩融胀”向“冻胀融缩”转变。应力-应变曲线特性与冻融循环次数和含水率都有较大的关系。试样的无侧限抗压强度随着含水率和冻融循环次数的增加而降低,其中以第1次冻融循环最为明显,3次后趋于稳定。函数拟合发现,试样的无侧限抗压强度与冻融循环次数呈明显的自然指数关系。含水率越大,冻融循环作用对土体微观结构的影响越大;土体的孔隙度随冻融循环次数的增加逐渐增大,第1次冻融循环作用最为明显,宏观上表现为冻融循环作用对土体力学性质的劣化影响。 |
关键词: 冻融循环 渠基膨胀土 体积变形 无侧限抗压强度 电镜扫描 |
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基金项目:国家自然科学(51879166);冻土工程国家重点实验室开放基金(SKLFSE201909) |
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Study on the influence of freeze-thaw cycles on the expansion-shrinkage deformation and mechanical properties of expansive soil |
chen yong, huang yinghao, zhu xun, wu min, wang shuo, zhu rui
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Geotechnical Engineering Department , Nanjing Hydraulic Research Institute
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Abstract: |
In order to explore the influence of the severe weather in the seasonal freezing area on the expansion and contraction deformation and physical and mechanical properties of the canal base expansive soil with different water content, the expansive soil in the Altay area of northern Xinjiang is taken as the research object, and the actual freeze-thaw changes in the northern Xinjiang area are simulated indoor The freeze-thaw cycle test under climatic conditions. Based on this, the volumetric deformation test, unconfined compressive strength test and Scanning electron microscope (SEM) test of the expansive soil with moisture content of 12%, 16%, and 20% are carried out, focusing on the analysis of the freeze-thaw cycle. The law of influence of action on volume deformation and mechanical properties of expansive soil. The results show that during the freeze-thaw cycle, with the increase of water content, the volume deformation of the sample changes from "freeze shrinkage and thaw expansion" to "freeze heave and thaw shrinkage". The characteristics of the stress-strain curve are closely related to the number of freeze-thaw cycles and the moisture content. The unconfined compressive strength of the sample decreases with the increase of the moisture content and the number of freeze-thaw cycles. Among them, the first freeze-thaw cycle is the most obvious, and it stabilizes after three times. The function fitting shows that the unconfined compressive strength of the sample has an obvious natural exponential relationship with the number of freeze-thaw cycles. The greater the water content, the greater the influence of freeze-thaw cycles on the microstructure of the soil; the porosity of the soil gradually increases with the increase in the number of freeze-thaw cycles. The first freeze-thaw cycle has the most obvious effect, which appears as freezing macroscopically. The effect of freeze-thawing cycle on the degradation of soil mechanical properties. |
Key words: Freeze-thaw cycle Expansive soil for channel foundation volume deformation unconfined compressive strength Scanning electron microscopy |