膨胀土干缩变形特性试验研究

Experimental Study on Volumetric Shrinkage Behavior of Expansive Soil

膨胀土是一种典型的问题性土,对气候变化非常敏感,在干旱气候条件下,极易发生体积收缩变形,引发各种工程地质问题。为了研究膨胀土的干缩变形特性,开展了一系列室内干燥试验,测定了膨胀土的收缩特征曲线,重点分析了初始含水率和干密度对干缩变形过程的影响,并进一步探讨了水泥固化抑制膨胀土干缩变形的效果和机理。结果表明:(1)膨胀土的干缩变形过程存在三个典型阶段:正常收缩、残余收缩和零收缩;(2)初始含水率越高,试样蒸发速率越快,且干缩变形完全后试样孔隙比越小而最终收缩应变越大,干缩变形越明显;(3)初始干密度越大,试样蒸发速率和最终体积收缩应变越小,提高初始干密度对试样干缩变形具有一定的抑制作用;(4)在膨胀土中掺入适量的水泥能显著降低试样的体积收缩应变,对干缩变形具有良好的抑制效果;(5)膨胀土的干缩变形具有明显的各向异性特征,并且与初始状态有关。

Expansive soil is a kind of typical soil with problems,which is very sensitive to climate change.it is prone to volumetric shrinkage deformation under drought conditions,causing various engineering geological problems.In order to study the desiccation shrinkage deformation characteristics of expansive soil,a series of indoor drying experiments were carried out to determine the shrinkage characteristic curves of expansive soils,and the effects of initial moisture content and dry density on the shrinkage deformation process were mainly analyzed.The effect and mechanism of cement solidification on suppressing desiccation shrinkage deformation of expansive soil are further discussed.The results show that:(1)There are three typical stages in the shrinkage deformation process of expansive soils:normal shrinkage,residual shrinkage,and zero shrinkage.(2)The higher the initial moisture content,the faster the evaporation rate of the sample,and the smaller the void ratio of the sample after the shrinkage deformation is complete,and the larger the final shrinkage strain,the more obvious the shrinkage deformation will be.(3)The larger the initial dry density,the smaller the sample evaporation rate and the final volume shrinkage strain,and the increase of the initial dry density has a certain inhibitory effect on the shrinkage deformation of the sample.(4)Incorporating proper amount of cement in expansive soil can significantly reduce the volumetric shrinkage strain of the sample,and it has a good suppressive effect on shrinkage deformation.(5)The dry shrinkage deformation of expansive soil has obvious anisotropic characteristics and is related to the initial state.