桂林红黏土干湿循环条件下饱和渗透系数及孔隙特征变化试验

Experiment on Saturation Permeability Coefficient and Pore Characteristicsof Guilin Red Clay under Dry-wet Cycle

以桂林红黏土为研究对象,采用抽真空饱和法、恒温干燥法对重塑土样作干湿循环,研究对渗透系数与干湿循环次数的关系,并结合压汞和电镜扫描分析不同循环次数下孔隙分布的变化特征。试验结果表明:桂林红黏土具有明显的片状结构,经过反复干湿循环,在孔隙水压力的作用下,孔隙孔径由双峰逐渐变为和原状土相似的单峰,中微孔隙都会向0.1~1.0μm的小孔隙靠近,孔隙孔径分布范围变小,在此过程中,游离土颗粒会被吸引在团聚体周围,使土粒孔隙形态更加平滑,且迂曲度与循环次数呈对数关系逐渐减小。压实重塑土样在经过3次干湿循环后,孔径结构变化基本稳定,渗透系数与同条件下原状土样相同,可替代无法获得符合试验条件的原状土样的结果。

Herein Guilin red clay was taken as the object to test the remoulded sample under dry-wet cycle by vacuum saturating method and constant temperature drying method and study the relation between the permeability coefficient and the number of dry-wet cycles and then,with mercury injection and electron microscope scanning,to analyze the variation features of pore distribution under different cycle times.The test result shows that,Guilin red clay is of obvious lamellar structure and,through repeated dry-wet cycles,the pore diameter gradually changes under the action of pore water pressure from double-peak to single-peak which is similar to that of undisturbed soil;the medium and micro pores will be close to the small pores between 0.1μm and 1.0μm,leading to smaller range of pore diameter distribution,during which the free soil particles will be attracted around the aggregates,leading to smoother pore shape;the tortuosity reduces gradually with logarithmic relationship to the number of cycles;for compacted remoulded soil sample,the change of pore structure after three dry-wet cycles is basically stable,moreover,its permeability coefficient is the same as that of undisturbed soil sample under the same conditions,hence it can replace the undisturbed soil sample that can not meet the test conditions.