压实膨胀土压实特性试验研究

Compaction behavior of compacted Maryland expansive soil considering microstructure effect

为了探究膨胀土在压实过程中的应力状态演变规律,利用自主研制的一维压实仪,针对澳大利亚马里兰(ML)膨胀土开展一系列不同初始含水率的压实试验,分析压实过程中的吸力及变形特性。研究结果表明,土体压实系数(Cc)受初始含水量影响显著,当初始含水量小于21.4%时,Cc随初始含水量增加而增加,当初始含水量大于21.4%时,Cc保持不变。土体回弹系数(Cr)不受初始含水量影响,压实过程中吸力因"力学增湿"而不断减小,卸荷后土体吸力显著增大。初始含水量相同时,卸载后吸力增加随饱和度增大而增大。基于压实后吸力,压实平面可分为吸力不受饱和度影响与吸力随饱和度增加而增大两部分;常体积下土水特征曲线受孔隙比影响显著;最后,利用基于吸力、饱和度、平均有效应力、修正吸力、孔隙比构建的水土特征曲线及压实曲线,对压实膨胀土中吸力及体积的变化进行了预测。

In order to study the evolution of stress status of expansive clay,a series of compaction tests for ML clay had been carried out. The samples with different initial water contents were compacted via a home-made onedimensional compaction apparatus. The evolutions of suction and deformation of samples were analyzed during the compaction process. It shows that compression index(Cc) is significantly affected by initial water content. The value of Cc increases with initial water content if the initial water content is smaller than 21.4%,otherwise it keeps almost constant. The initial water content has little effect on the unloading-reloading index(Cr). Due to the “mechanical wetting”effect,the matric suction gradually decreases during compaction. During the unloading stage,the matric suction increases significantly. For the sample with same initial water content,the increment of matric suction due to unloading effect increases with the degree of saturation. Based on the post-compaction suction,the compaction plane could be divided into parts:the post-compaction suction is not affected by the degree of saturation of samples,and the post-compaction suction increases with degree of saturation. It also clearly shows that soil water retention curve of sample with constant volume is strongly affected by the void ratio. Based on suction,the degree of saturation,average effective stress,modified suction and void ratio,models for soil water retention curve and compaction curve have been established. The predict of suction and volume evolution during the compaction has been carried out.