反复湿化和动载作用下路基红黏土累积变形特性研究

针对南方湿热地区红黏土路基受干湿交替环境和行车荷载往复作用而出现过大附加沉降的问题,为揭示反复湿化和动载联合作用下路基红黏土的累积变形演变规律,采用喷雾加湿和暖风干燥的方法对压实红黏土试样进行定量增湿与脱湿,制备了4个不同湿化幅度和5种不同湿化次数的试样,并通过动三轴试验测试了湿化幅度、湿化次数和动应力幅值对累积变形的影响。研究结果表明:累积塑性应变随湿化幅度的增加呈非线性增大,存在临界湿化幅度为1.5%,超此幅值时累积应变成倍增加;试样经历初次湿化时,即从0次到1次,累积应变增幅较大,第2次和第3次时增幅放缓,而进行到第4次时,累积应变增幅又变大;动应力较小时,累积应变在较少振动次数下趋于稳定,而当动应力超过临界动应力水平,试样累积应变迅速增长直至破坏,且动应力对累积塑性应变的影响随着反复湿化幅度和次数的增加而增大;累积应变状态受湿化幅度、湿化次数和动应力幅值的耦合影响,从塑性安定型演变为增量破坏型,其典型滞回曲线形状由从疏到密变化到从密到疏,面积越来越大。最后基于试验加载结束时累积应变的幂函数变化规律,以湿化幅度、湿化次数和动应力幅值为变量,建立了动力湿化应变的预测模型,可用于实际工程常出现的稳定型累积应变状态的湿化变形预测。

Accumulative Deformation Characteristics of Lateritic Clay Under Combined Action of Cyclic Wetting and Dynamic Loading

To address the problem of excessive additional settlement of lateritic clay subgrade in hot and humid areas of southern China,the accumulative deformation evolution of compacted lateritic clay under the combined action of cyclic wetting and dynamic loading was investigated in this study.Spray humidification and warm air drying were used to quantitatively humidify and dehumidify soil samples,and test specimens were prepared at four different moisture contents and five different wetting cycles.Repeated loading triaxial tests were conducted to investigate the effects of wetting amplitudes,wetting cycles,and dynamic deviator stress on accumulative deformation.The test results show that the accumulative plastic strain increases nonlinearly with an increase in the wetting amplitude,and the critical wetting amplitude is equal to 1.5%.The accumulative strain increased significantly when the wetting amplitude exceeded the critical value.When the sample was humidified for the first cycle,the increase in accumulative strain was large,and it slowed down in the second and third cycles,and increased again in the fourth cycle.When the dynamic stress was small,the accumulative strain tended to be stable with less cyclic loading.As the dynamic stress exceeded the critical dynamic stress level,the accumulative strain increased rapidly until failure,and the effect of dynamic stress on the accumulative plastic strain increased with an increase in the wetting amplitude and cycles.Under the coupling influence of wetting amplitude,wetting cycles and dynamic stress amplitude,the accumulated strain state evolved from plastic shake-down to progressive failure,and its typical hysteretic curve shape changed from "sparse to dense" to "dense to sparse" and the area kept increasing.Finally,based on the power function variation law of accumulative strain at the end of test loading,the prediction model of dynamic wetting strain was established with wetting amplitude,wetting cycles,and dynamic stress amplitude as variables,which can be used to predict the wetting deformation of the stable state of the accumulative strain,which often occurs in practical engineering.