水位下降条件下西安D7裂缝土体孔隙变化特征试验

An analysis of pore structure,pore fractal feature based on decline of groundwater in compressive soil:An example from soil mass besides Xi′an D7 ground fissure

为研究压缩性土体在孔隙水压力下降下所引起的孔隙变化特征,选取孔隙度及分形维数作为评判指标,以西安D7地裂缝两侧可压缩性土层为研究对象,借助三维CT扫描成像技术,依托Matlab计算平台及VG Studio Max图像处理软件,对在水位下降过程中可压缩性土体压缩变形引起的孔隙度和分形维数孔隙变化进行定量评价,并探讨了固结压缩过程中土体孔隙分形维数的变化规律及其影响因素。研究表明:孔隙度随压缩进行大幅降低,由压缩前4.36%降至0.61%;土体分形维数与孔隙度、上覆压力均呈线性相关性,相关系数分别为0.947 2和0.966 0;而且分形维数可以很好的表征孔隙分布特点,是孔隙度的有效补充;通过分析土样孔隙度与分形维数关系,为后期建立区域上地裂缝—地下水开采耦合模型提供参数赋值基础。

In order to study the variation of compressive soil pores caused by decrease of pore water pressure,we studied thecompr essive soil on the two sides of the D7ground fissure in Xican.Using the threedimensional CT imaging technique,Matlabcomputing platform and VG Studio Max program,we calculated the porosity and fractal dimension variations caused by thecompression deformation of compressive soil during the drop of water level,and discussed the influence factors and variationpatterns of the porosity and fractal dimension in the consolidation process.The results showed that the por osity declined from4.36%to0.61%with the compression,and that the fractal dimensio n had a linear co rrelation with both the porosity and overburden pressure,at a correlation coefficient of0.9237and0.9660respectively.As an effective supplement of the porosity,fractal dimension could well represent the distribution character istics of the pores.By analyzing the relationship between porosityand fractal dimension,the study results may provide parameter assignment basis for the fissureg roundwater pumping coupledmodel.