干密度和温度对冻结膨胀土单轴压缩特性影响的试验研究北大核心CSCD

膨胀土是一种特殊的黏土,具有明显的胀缩性和多裂隙性,在寒区渠道工程中极易诱发各种冻害。单轴压缩特性是冻土物理力学特性的重要分支,为研究冻结膨胀土的单轴压缩特性,开展了不同干密度和温度下冻结膨胀土单轴压缩试验。试验结果表明:随着干密度的增加,各温度工况下试样的应力-应变关系曲线均由弱应变软化转为应变硬化形态,且试验温度越高,曲线的软化特征越显著。不同温度工况下试样的破坏模式差异明显。当试验温度为-2℃时,试样破坏时其表面出现明显的局部坍塌与剥落,而-5℃、-10℃和-15℃工况下试样的最终破坏形态均为“鼓状”破坏,试样表面无明显的裂缝和剪切面。冻结膨胀土试样的单轴抗压强度随干密度的增加而线性增大,亦随温度的降低而增大,但在不同的温度区间内增幅不同,其变化幅度主要与试样内部含冰量密切相关。此外,试样的弹性模量随着干密度的增大和温度的降低均线性增大。

Experimental study on the influence of dry density and temperature on the uniaxial compression characteristics of frozen expansive soil

Expansive soil is a kind of special clay， which has obvious swell-shrink characteristics and multiple fissures. It is very easy to induce various freezing damages in channel engineering in cold regions. Uniaxial compression is an important branch of physical and mechanical characteristics of frozen soil. In order to investigate the uniaxial compression characteristics of frozen expansive soil， a series of uniaxial compression tests considering different dry densities and temperatures were carried out， and the effects of dry density and temperature on the stress-strain relationship， failure mode， compressive strength and elastic modulus of frozen expansive soil were discussed. The test was carried out on low temperature dynamic testing machine in the frozen soil laboratory of Hohai University. The compression test was carried out at a constant rate. When the axial strain reached 30%， the test was stopped （except for the brittle failure sample）. The test results show that the stress-strain relationship curve of the sample under various temperatures gradually changes from weak strain softening to strain hardening with the increase of dry density. The higher the temperature， the more significant the softening characteristics of the stress-strain curve. The failure mode of samples under different temperatures are obviously different. Obvious local collapse and spalling appear on the surface when the sample is damaged at -2 ℃， while the final failure mode of samples at -5 ℃， -10 ℃ and -15 ℃ is “drum-like” failure， accompanied with few obvious cracks and shear planes on the sample surface. The uniaxial compressive strength of frozen expansive soil samples increases linearly with the increasing dry density. Besides， the uniaxial compressive strength of the samples also increases with decreasing temperature， however， there are some differences in its amplification within each temperature range， which is closely related to the ice content in samples. In addition， the elastic modulus of the sample increases linearly with the increasing dry density and decreasing temperature. The research results are expected to provide reference for the freezing damage mechanism of channel engineering and the treatment of channel foundation soil in the expansive soil section in the cold region.