冻融作用对原状黄土抗剪强度的影响规律
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TU411.7

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青海省科学技术厅项目(2018-ZJ-933Q、2018-ZJ-T01)


Effect of freezing and thawing on shear strength of intact loess
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    摘要:

    以西宁市某区域内原状黄土为研究对象,设计封闭系统下的三向慢速冻结试验、恒温恒湿的融化试验以及三轴剪切试验。基于土的莫尔-库伦强度理论,利用抗剪强度包线求解黏聚力和内摩擦角,研究不同冻融温度梯度下抗剪强度指标的变化规律。结果表明:随着温度梯度增大,黏聚力衰减速度显著,衰减为极小值时的最不利冻融温度梯度为-15~15℃;冻融黄土的黏聚力与冷端温度、融化温度有关;较低含水率和较小冷端温度耦合作用或较高含水率和较大冷端温度耦合作用时,与冷端温度相比,融化温度为主导影响因素。随着冷端温度的增大,不同含水率试样的黏聚力降低幅度呈先减小、后增大的规律,最不利的含水率为18.34%。内摩擦角呈现出不规律性波动,变化幅度约为0~14°。由试验数据拟合出黏聚力随冷端温度和含水率变化规律的计算式,经试验验证,计算式能较好地描述其变化特性。

    Abstract:

    Taking the intact loess in a certain area in Xining as the research object, they were designed the three direction's slow freezing test under the closed system, the constant temperature and humidity thawing test and the triaxial shear test. Based on the Mohr-Coulomb strength theory of soil, the cohesion and internal friction were solved by using the shear strength envelope, and the variation of shear strength indexes under different freezing thawing temperature gradients are studied.The results show that:with increase of temperature gradients, the cohesion decay rate is remarkable, and it is -15~15℃ for the most disadvantageous freeze-thaw temperature gradient when the cohesion is minimum;The cohesion of frozen-thawed loess is related to the cold end temperature and thawing temperature;Compared with cold end temperature, the thawing temperature is the dominant factor when the moisture content is lower and the temperature at the cold end is lower, or the temperature at the cold end is higher. With the increase of the cold end temperature, the cohesion of samples with different moisture contents decrease firstly and then increase, the most disadvantageous moisture content is 18.34%.The internal friction shows irregular fluctuations, and the extent of variation is about 0°~14°. The calculation formula of the cohesion with the cold end temperature and moisture content is fitted by the experimental data. The experimental formula can better describe the variation characteristics of cohesion.

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李双好,李元勋,高欣亚,石冬梅.冻融作用对原状黄土抗剪强度的影响规律[J].土木与环境工程学报(中英文),2020,42(1):48-55.

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  • 收稿日期:2019-04-19
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  • 在线发布日期: 2020-03-07
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