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循环荷载下路基黏土永久变形特性及力学模型

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为了合理表征路基土的永久变形特性,用分数阶Abel黏壶替换黏塑性模型中的整数阶牛顿黏壶,在此基础上串联一个范德普模型,构建了路基土的非线性黏弹塑性元件模型.根据黏弹塑性力学理论,推导了循环荷载下路基土永久变形的力学模型,并使用该模型对长沙典型黏土的永久变形试验结果予以辨识.研究结果表明:分数阶黏弹塑性力学模型能够与永久变形试验曲线很好吻合;荷载的作用时间增长及间歇时间缩短均会导致路基黏土永久变形增大,间歇时间的影响存在临界值,超此临界值永久变形基本不变;循环应力幅值增大或围压减小时,永久变形均随之增大,且累积变形速率变快;永久变形受湿化作用影响显著,含水率小幅增长即可使永久变形成倍增加,且当含水率由中低水平升高至较高水平时,永久变形由塑性安定型转变为塑性蠕变型,发展状态不再收敛.对力学模型参数进行敏感性分析发现,黏弹性参数G1和η1对各个影响因素的敏感性极低,黏塑性参数β和η2与荷载作用时间、荷载间歇时间、循环应力幅值、围压以及含水率等具有较强的相关性,进而建立了参数β和η2的多元回归方程.验证结果显示推导的力学模型可较为准确地描述路基黏土的永久变形,以用于循环荷载下黏性土路基永久变形的数值计算与分析.
Characterization and Mechanics Modeling of Permanent Deformation of Subgrade Clay Under Cyclic Loading
To ensure comprehensive characterization of the permanent deformation(PD)properties of subgrade clay,a conventional integer-order Newton dashpot was substituted with a fractional-order Abel dashpot within the viscoplastic model.To extend this innovation,a Van Der Poel model was integrated in series to construct a nonlinear viscoelastic-plastic component model of subgrade clay.Based on viscoelastic-plastic mechanics theories,a mechanical model of the subgrade clay's PD was developed and calibrated using the test results of the conventional clay in Changsha.The results show that the fractional-order viscoelastic-plastic mechanical model aligns with the PD test curves.The PD of the subgrade clay exhibits a notable tendency to increase,corresponding to a longer loading action duration and a shorter intermittent loading duration.A critical threshold must be reached for intermittent loading duration to have an effect,and the PD remains constant beyond this threshold.An increased cyclic stress amplitude or a diminished confining pressure increases the PD,followed by an increased cumulative growth rate.Humidity has a significant effect on PD because even a slight increase in moisture content increases the observed PD value twice.Furthermore,as the moisture content progressively transitions from a relatively low to a substantially high threshold,the PD experiences a notable shift in behavior,transitioning from plastic shakedown to plastic creep,resulting in an unconverted development state.The sensitivity analyses of mechanical model parameters show that the viscoelastic parameters G1 and η1 exhibit a negligible sensitivity to the associated influence factors.In contrast,the viscoplastic parameters β and η2 display a robust and significant correlation with the loading action duration,loading intermittent duration,cyclic stress amplitude,confining pressure,and moisture content.Consequently,multiple regression equations were obtained to estimate βand η2.The verification results show that the mechanical model can accurately capture the PD characteristics of the subgrade clay and be used for the numerical calculation and analysis of the PD of a subgrade filled with clay under cyclic loading.

subgrade engineeringsubgrade claydynamic triaxial testpermanent deformationmechanical modelfractional derivative

张军辉、张安顺、彭俊辉、胡惠仁

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长沙理工大学公路养护技术国家工程研究中心,湖南长沙 410114

湘江实验室,湖南长沙 410205

路基工程 路基黏土 动三轴试验 永久变形 力学模型 分数阶导数

国家杰出青年科学基金项目湘江实验室重大项目国家自然科学基金项目国家自然科学基金项目湖南省研究生科研创新项目长沙理工大学公路养护技术国家工程研究中心开放基金项目

5202508522XJ010095233800952208419CX20210748kfj210101

2024

10.19721/j.cnki.1001-7372.2024.06.002

中国公路学报
中国公路学会

中国公路学报

CSTPCD北大核心
影响因子：1.607
ISSN：1001-7372
年,卷(期)：2024.37(6)
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