黄泛区中高液限黏土动、静态回弹模量及预估模型研究

土体回弹模量是路基填料的重要力学指标和路面结构的主要设计参数。针对黄泛区中高液限黏土，开展了3种压实度、3种含水率和3种围压、7种附加应力水平下的动、静三轴试验研究，分别获得了189组工况下的动、静态回弹模量及其相关关系。研究结果表明：土体回弹模量与物理状态和应力水平密切相关，且土体动态回弹模量普遍高于其静态值，动态回弹模量以及动、静回弹模量比均随着偏应力比（附加应力与围压比值）的增加而呈指数式衰减，并可划分为快速衰减区、过渡区和缓慢衰减区，对应的偏应力比分别为0.2~1.0，1.0~2.0和2.0~3.0；在此范围内，土体的动态回弹模量为其静态回弹模量的1.21~1.91倍；同时，获得了土体归一化动态回弹模量与回弹应变的相关关系，提出了黄泛区中高液限黏土归一化动态回弹模量表达式，在偏应力比为0.2~3.0范围内，土体的回弹应变为34×10^-6~2 200×10^-6，处于变化敏感的小应变水平，归一化动态回弹模量随着应变的增加而快速减小，最大衰减至0.54，计算路基顶部竖向压应变的设计指标时，需要考虑动态回弹模量的衰减；最后，对现行规范的土体动态回弹模量预估模型进行了修正，提出了适合黄泛区中高液限黏土的三参数经验公式，并且建立了土体双参数静态回弹模量预估模型，对9种不同物理状态下的土体静态回弹模量进行了可靠预测。

Dynamic and Static Resilient Modulus and Their Prediction Models of Medium-high Liquid Limit Clay in Yellow River Flooded Areas

Soil resilient modulus,an important mechanical index for subgrade fillings,is the main parameter for pavement design.In this paper,both static and dynamic triaxial tests were performed on the medium-high liquid limit clay in the Yellow River flooded areas.These tests were carried out for different sets of conditions including three compaction degrees,three moisture contents,three confining pressure and seven additional stresses.The characteristics of both static and dynamic modulus as well as their relationships were obtained for all 189 sets of testing conditions.The results show that soil resilient modulus is associated with its physical states and stress levels,and the dynamic resilient modulus is generally higher than the static value.The dynamic resilient modulus and the ratio between the dynamic and static resilient modulus decrease exponentially with increasing deviatoric stress ratio,which is defined as the ratio between additional stress and confining pressure.It can be divided into the following three stages:rapid decrease,transition zone and slow decrease,corresponding to the deviatoric stress ratio ranges of 0.2-1.0,1.0-2.0 and 2.0-3.0,respectively.Additionally,the dynamic resilient modulus is found to be 1.21-1.91 times higher than the static resilient modulus.The relationship between the normalized dynamic resilient modulus and the resilient strain is obtained,and the formula of the normalized dynamic resilient modulus is proposed.The dynamic resilient modulus is found to attenuate rapidly to 0.54 when the resilient strain increases from 34×10^-6 to 2200×10^-6,at the sensitive small strain range,within the deviatoric stress ratios of 0.2-3.0.This suggests that such a reduction in dynamic resilient modulus should be considered for the calculation of the design index of vertical compression strain at subgrade surface.Finally,the prediction model of the dynamic resilient modulus is modified according to the current design specifications,and a new three-parameter model is proposed for the medium-high liquid limit clay in the Yellow River flooded areas.Moreover,a two-parameter model is also put forward for the static resilient modulus,which provides reliable results for all nine physical states.