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黄河冲积平原区粉土路基具有强烈的毛细现象及水敏性特征,在外界水环境综合影响下含水率普遍偏高,路基支撑强度不足,路面结构早期破损严重。击实试验发现黄河冲积粉土由于级配不良、粒间空隙大等因素造成压实困难,其击实曲线在低含水率与高含水率时分别表现为部分无黏性土与黏性土特征,变形特性复杂。为了分析粉土路基的吸水特性,进行了降雨渗透、毛细水上升室内模拟试验,发现二者对粉土含水率均有显著的影响,且毛细水上升速度高于降雨入渗速度,上升高度可达1.5 m。现场实测表明,低路基(H<2.5 m)含水率沿深度方向的分布呈“底部最大、顶部次之、中间最小”的变化特征,而一般标高路基(H≥2.5 m)则表现为底部含水率偏高、中上部含水率较低,但均高于最优含水率。不同含水率下压实粉土回弹模量及三轴试验结果表明,当实际含水率高于最优含水率时,路基土回弹模量、变形模量及黏聚力随含水率的增大都呈显著的衰减关系,当接近饱和状态时内摩擦角也急剧降低,从而揭示出粉土路基在吸水后将具有变形大、强度低的特点,易造成路面结构早期病害。针对不同路基高度,推荐了相应的路基设计模量。
The silt subgrade in the alluvial plain of the Yellow River has a strong capillary phenomenon and water sensitivity characteristics. Under the combined influence of the external water environment, the water cut is generally high and the supporting strength of the subgrade is not sufficient, and the pavement structure is seriously damaged in the early stage. Compaction tests showed that compaction difficulties were found in the alluvial silt in the Yellow River due to poor gradation and large intergranular voids. The compaction curve of the alluvial silt in the Yellow River showed some characteristics of non-cohesive soil and cohesive soil at low water cut and high water cut , The deformation characteristics of complex. In order to analyze the water absorption characteristics of silt subgrade, rainfall infiltration and capillary water rise indoor simulation test were conducted. It was found that both of them had a significant effect on the silt moisture content, and the capillary water rise rate was higher than the rainfall infiltration rate. Up to 1.5 m. Field measurements show that the distribution of moisture content along the depth of low embankment (H <2.5 m) is characterized by “bottom maximum, top bottom and middle minimum”, while the general elevation subgrade (H≥2.5 m) The bottom moisture content is high, middle and upper moisture content is lower, but higher than the optimal moisture content. Resilient modulus and triaxial test results of compacted silts under different water contents show that when the actual water content is higher than the optimal water content, the modulus of return, deformation modulus and cohesion of subgrade soil increase with the increase of water content Most of them show a significant decay relationship. When approaching the saturation state, the internal friction angle decreases sharply, which reveals that the silt subgrade will have the characteristics of large deformation and low strength after water absorption, which will easily cause the early damage of pavement structure. For different subgrade heights, we recommend the corresponding subgrade design modulus.