基于蠕变试验的路基压实黄土流变本构模型研究

Rheological constitutive model of compacted loess based on creep test

结合具体试验路段,运用载荷装置与高压固结仪对不同能级强夯条件下的压实黄土进行蠕变试验,探讨压实度和含水量对压实黄土结构屈服强度的影响,建立可反映压实黄土流变特性的本构模型。研究结果表明:在蠕变应力小于土体的结构屈服强度时,地基土体主要表现为衰减蠕变;蠕变应力大于土体的结构屈服强度时,其蠕变类型主要表现为稳定蠕变;当蠕变应力远大于土体的结构屈服强度时,其蠕变类型主要表现为加速蠕变。一维高压固结条件下土样的塑性残余变形与含水量近似呈线性关系,压实度和含水量与结构屈服强度呈指数关系。原状黄土的回滞环形态上呈狭窄的条形,而压实黄土则呈新月形;载荷试验条件下压实黄土不同阶段分别表现为线性黏弹性和非线性黏塑性流变特征,可建立压实黄土流变本构模型反映其应力应变基本规律。

Combined with the specific test section, the load device and the high pressure consolidation apparatuswere used for the creep test of compacted loess under different levels of dynamic compaction. The influence ofcompaction degree and water content on yield strength of compacted loess structure was studied, and theconstitutive model which can reflect the rheological properties of compacted loess was established. Results showthat, with the creep stress less than the structure yield strength, the creep types of soil mainly manifest asattenuation creep. With the creep stress greater than the structure yield strength of the soil, the creep types mainlymanifest for steady creep. With the creep stress far greater than the soil structure yield strength, the creep typesmainly manifest accelerated creep. The plastic residual deformation of the soil sample under one dimensional highpressure consolidation has a linear relationship with the water content. The degree of compaction and moisturecontent are in exponential relationship with the yield strength of the structure. The shape of the hysteresis loop ofthe undisturbed loess is a narrow strip shape, while the compacted loess has a crescent shape. The different stagesof compacted loess are shown as linear viscoelasticity and nonlinear visco plastic rheological characteristicsrespectively, and the constitutive model of compacted loess can be established to reflect the basic law of stress-strain.