冻融循环下低液限盐渍化粉土力学特性研究
Study on the Mechanical Characteristics of Salinized Silt Soil with Low Liquid Limit under Freeze-Thaw Cycle
包卫星 1秦川 1李伟 1刘亚伦 1陈锐1
作者信息
摘要
为了研究冻融作用对低液限盐渍化粉土强度的影响,对不同初始含水率低液限盐渍化粉土进行冻融循环试验后,开展不固结不排水(UU)剪切和扫描电镜(SEM)试验,从宏微观角度揭示低液限盐渍化粉土强度的劣化机理.结果表明:未冻融时,含水率的改变不会引起低液限盐渍化粉土应力-应变曲线形态发生变化,均表现为软化型;在冻融作用下,含水率小于14％时试件的曲线形态不会发生改变,呈现软化型,高含水率的试件其应力-应变曲线形态会向着硬化性转变;通过分析冻融和含水率与破坏强度的关系,发现低液限盐渍化粉土破坏强度随含水率的提高呈现线性衰减,破坏强度随冻融循环次数的增加呈现指数型衰减,前3次冻融过程中破坏强度的衰减速率和幅度最大,随后趋于稳定;随着围压的增大,试件的应力-应变曲线会由软化型向硬化型过渡;在微观结构方面,冻融作用会改变土颗粒之间的接触形式,造成孔隙和裂隙的发育,冻融过程中微观结构的变异规律和宏观力学指标的劣化具有一致性.结合土体损伤力学,构建了冻融作用下的低液限盐渍化粉土黏聚力损伤劣化模型,冻融过程中的劣化度符合双曲线关系,最终劣化度Ac与含水率呈指数型关系,劣化速率Bc与含水率呈线性关系.
Abstract
In order to study the effect of freeze-thaw on the strength of low-liquid limit salinized silt,after the freeze-thaw cycle test of salted silt with different initial moisture content,non-consolidating and non-drainage(UU)shear and scanning electron microscopy(SEM)tests were carried out to reveal the deterioration mechanism of the strength of low-liquid limit salinized silt from macro-micro perspectives.The test results show that the change of moisture content does not cause the stress-strain curve morphology of low-liquid limit salinized silt to change when it is not freeze-thawed,and all of them are softening.Under the action of freeze-thaw,the curve shape of the specimen will not change when the moisture content is less than 14％,showing a softening type,and the stress-strain curve shape of the specimen with high moisture content will change to hardening.By analyzing the relationship between freeze-thaw and moisture content and failure intensity,it is found that the failure intensity of low-liquid limit salted silt decays linearly with the increase of moisture content,and the failure intensity decays exponentially with the increase of freeze-thaw cycles,and the attenuation rate and amplitude of the failure intensity are the largest in the first three freeze-thaw processes,and then tend to be stable.With the increase of confining pressure,the stress-strain curve of the specimen will transition from softening type to hardening type.In terms of microstructure,freeze-thaw will change the contact form between soil particles,resulting in the development of pores and fissures,and the variation law of microstructure and deterioration of macroscopic mechanical indicators in the freeze-thaw process are consistent.Combined with the soil damage mechanics,a low-liquid limit salinized silt cohesion damage deterioration model under freeze-thaw action was constructed,and the deterioration degree during the freeze-thaw process conformed to the hyperbolic relationship,and the final deterioration degree Ac had an exponential relationship with the moisture content,and the deterioration rate was Bc linear relationship with the moisture content.
关键词
低液限盐渍化粉土/冻融循环/力学性质/劣化模型/微观结构Key words
low liquid limit salinized silt/freeze-thaw cycle/mechanical properties/deterioration model/microstructure引用本文复制引用
基金项目
新疆重大科技专项(2020A03003-7)
陕西省自然科学基础研究计划面上项目(2021JM-180)
中央高校基本科研业务费资助项目(领军人才计划)(300102211302)
出版年
2024
NETL
NSTL
万方数据