土体干燥过程中的体积收缩变形特征

Volumetric shrinkage characteristics of soil during drying

通过开展室内试验,分别研究了初始饱和的糊状试样和不同压实状态的压实试样的体积收缩变形特征。对于糊状试样,采用液体体积置换法测量了试样干燥过程中的体积变化,获得了完整的收缩曲线,试验结果表明:糊状试样的收缩过程可分正常收缩、残余收缩和零收缩3个阶段;绝大部分收缩变形发生在进气点之前即土体处于饱和状态。对于压实试样,初始干密度和含水率对收缩特征有重要影响:初始干密度增加对体积收缩变形起抑制作用,而初始含水率的增加对体积收缩变形起促进作用。此外,压实试样的体积收缩存在明显的各向异性,且对初始含水率的敏感程度高于初始干密度。最后,根据试验结果,提出了压实试样收缩应变与初始干密度和含水率之间的函数关系式。

Drying shrinkage is one of the intrinsic characteristics of soil,and has profound effects on its engineering properties.In this investigation,laboratory tests are conducted on initially saturated paste-like specimens and compacted specimens with different compaction parameters.For the paste-like specimens,the fluid volume displacement technique is employed to measure the volumetric change of specimens during drying,and the complete shrinkage curve is determined.It is found that three stages can be distinguished in the shrinkage of paste-like specimens,namely normal shrinkage,residual shrinkage and zero shrinkage;most of the volumetric shrinkage deformation occurs before the air-entry point while the soil is still fully saturated;the volume shrinkage behavior and shrinkage curve shape significantly depend on soil microstructure characteristics.For the compacted specimens,the shrinkage behavior is significantly controlled by the initial drying density and water content.In general,shrinkage strain decreases with the increase of the initial dry density and increases with the increase of the compaction water content.In addition,the results show that the shrinkage of compacted specimens is anisotropic rather than isotropic,and is more sensitive to the initial water content than the initial dry density.A coupled linear and exponential equation is finally developed from the obtained data to describe the shrinkage strain at the given initial drying density and water content.