疏浚淤泥固化土宏微观孔隙结构特征及其对渗透性影响

Macro and micro pore structure characteristics of dredged silt solidified soil and its effect on permeability

采用压汞试验、渗透率试验和孔隙度试验等方法,研究疏浚淤泥固化土(DSSS)的孔隙度、微观孔隙结构特征、渗流特征及其相互关系.压汞试验结果显示,DSSS的孔隙体积频率分布曲线均为典型的双峰曲线,存在两个集中的孔喉半径区间:0.02~0.04μm和3~30μm.基于DSSS水化反应生成的致密水化产物和孔隙体积频率分布曲线,将DSSS的孔隙直径进行分组,微孔组和中孔组处于峰值区间,微孔组的最可几孔径随着初始密度和养护龄期的增加逐渐增大,中孔组的最可几孔径随着初始密度和养护龄期的增加逐渐减小.另外,孔隙度和渗透率试验结果显示,DSSS有效孔隙度随养护龄期逐渐减小主要发生在固化28d前,28d后DSSS有效孔隙度基本保持不变,而DSSS渗透系数仍在降低,在该阶段50%以上的中孔向小孔和微孔转化.因此,提出采用有效孔隙度作为表征DSSS的宏观孔隙特征参数,采用孔径和体积频率值作为表征微观孔隙特征参数,并采用毛细模型建立宏微观孔隙结构参数和渗透性之间的定量关系.

The porosity,micro pore structure characteristics,permeability properties of dredged silt solidified soil(DSSS)and their relationships are investigated by using mercury intrusion porosimetry(MIP)test,permeability test and porosity test.The results of MIP tests show that the frequency distribution curve of pore volume of DSSS presents a typical bi-peak distribution,and the two concentrated pore throat radius intervals are 0.02-0.04μm and 3-30μm.The pore diameter of DSSS is divided into groups according to the compact structure of hydration product of DSSS and the frequency distribution curve of pore volume.The micropore group and the mesopore group are in the peak interval.The most possible aperture of the micropore group increases with the increase of initial density and curing age.The most possible aperture of the mesopore group decreases with the increase of initial density and curing age.Besides,the results of porosity test and permeability test show that the effective porosity of DSSS gradually decreases with curing age during the first 28 days and the effective porosity remains unchanged after curing for 28 days.While,the permeability coefficient of DSSS still decreases after curing for 28 days,and over 50%of the mesopores at this stage are transformed into small pores and micropores.Hence,the effective porosity,the pore size and volume frequency value are proposed to present the characteristic parameters of macroscopic and microscopic pore structure of DSSS respectively,and a capillary model is used to quantitatively correlate the permeability with macro and micro pore structure parameters.