压缩过程中非饱和膨胀土体变特征与持水特性的水力耦合效应

发布时间：2018-03-30 18:11

本文选题：非饱和土　切入点：压实膨胀土　出处：《岩土工程学报》2015年04期

【摘要】：土体压缩是岩土工程领域的基本问题。压缩过程中非饱和土的力学与水力学行为是同时发生且相互影响的,有必要统一考察体变特征与持水特性的水力耦合效应。为此,以荆门弱膨胀土为研究对象,开展土中水密度试验、饱和与控制吸力下的非饱和一维压缩试验,准确测量了压缩与卸荷回弹过程中孔隙比重力含水率吸力竖向净应力关系,探讨了水力耦合状况下非饱和膨胀土的体变特征与持水特性规律,并建立相应本构描述。结论如下:1加载段,非饱和压缩曲线均发生明显转折,体现出屈服行为;随吸力增大,压缩曲线依次发生"穿越"现象;卸载段大体呈线性,其斜率随吸力增大而降低。提出能够描述干缩、压缩、卸荷体胀、屈服、压缩性与卸荷回弹性随吸力变化等行为的非饱和土体变方程,可直接用于分层总和法计算。2不同吸力下重力含水率变化存在较大差异;压缩至2941.8 k Pa时,不同吸力下含水率非常接近。吸力与竖向净应力对含水率变化的耦合影响可用3参数Logistic函数描述。3压缩过程中饱和度随竖向净应力增大而增大,卸荷过程中随竖向净应力降低亦增大。采用饱和度或重力含水率,对压缩过程中的水力路径会出现"湿化"与"脱湿"的不同判断,即水力耦合状况下土体表现出复杂的持水状态变化特征。
[Abstract]:Soil compression is a fundamental problem in geotechnical engineering. The mechanical and hydraulic behaviors of unsaturated soils occur at the same time and interact with each other during compression. Taking Jingmen weakly expansive soil as the research object, the water density test in the soil and the unsaturated one-dimensional compression test under saturated and controlled suction were carried out. The vertical net stress relationship between void ratio and gravity moisture content and suction during compression and unloading springback is accurately measured, and the characteristics of bulk deformation and water holdup of unsaturated expansive soil under hydraulic coupling are discussed. The corresponding constitutive description is established. The conclusions are as follows: the unsaturated compression curves have obvious turning points in the loading section of 1: 1, which reflect the yield behavior; with the increase of suction, the compression curve occurs "traversing" in turn, and the unloading section is generally linear. The slope decreases with the increase of suction. An equation of variation of unsaturated soil is proposed, which can describe the behavior of dry shrinkage, compression, expansion of unloading body, yield, compressibility and unloading elasticity with suction. This method can be directly used to calculate the variation of gravity water content under different suction, and when compressed to 2941.8 KPA, The coupling effect of suction and vertical net stress on the variation of water content can be described by using 3-parameter Logistic function to describe that the saturation increases with the increase of vertical net stress. In the process of unloading, the vertical net stress also increases with the decrease of vertical net stress. By using saturation or gravity moisture content, the different judgment of "humidification" and "dehumidification" will appear in the hydraulic path during compression. In other words, the soil shows complex characteristics of water retention under hydraulic coupling.
【作者单位】：信阳师范学院土木工程学院;岩土力学与工程国家重点实验室(中国科学院武汉岩土力学研究所);
【基金】：国家自然科学基金项目(51009118) 中国博士后科学基金项目(20100470058)
【分类号】：TU443

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