冲击压实路基黄土的微观特征研究

Microstudy on roadbed loess improvement by impact compaction technology

采用扫描电镜和压汞试验研究了天然黄土和冲击压实8～40遍路基黄土的微观结构和孔隙特征。结果表明:天然黄土和冲击压实8遍的路基黄土,其微结构以粒状架空结构为主;冲击压实16～40遍,土的微结构变成粒状镶嵌结构。冲击压实16遍前后,土的孔隙直径分布在0.006～164μm之间,平均孔径从0.767 9μm降低到0.0 711μm,中等孔径从5.264μm减少到0.568 4μm;但孔隙表面积从0.624 m2/g增加到7.517 m2/g。孔径分布在10μm和2μm处出现分界值,16遍前2<d≤10μm的孔隙占67.53%,而16遍后d≤2μm的孔隙占68.07%。最佳的冲击压实遍数为16遍。冲击压实16遍后,土微结构的改变和小孔隙的增多为冲击压实技术加固黄土路基的机理。

The microstructure and pore characteristics of natural loess and roadbed loess improved by impact compaction after 8-40 compactor passes were qualitatively and quantitatively studied on the basis of the test results from scanning electron microscope （SEM） and mercury intrusion porosimetry（MIP）. The results show that open structure is the main structure type of natural loess and roadbed loess after 8 compactor passes; and inter-particle inlaid structure is the main type of roadbed loess after 16-40 compactor passes; The pore size distribution is within the range of 0.006-164 μm before and after 16 compactor passes, the average pore diameter has been lowered from 0.767 9 μm to 0.071 1 μm; the median pore diameter has been decreased from 5.264 μm to 0.5684 μm. The pore surface area has been increased from 0.624 m^2/g to 7.517 m^2/g; there are two dividing pore diameters of 10 μm and 2 μm for all types of loess, and for the loess before 16 compactor passes, the pores with diameter between 2 to 10μm cover 67.53 % of all the pores, while the pores with diameter less than 2μm cover 68.07 % for loess after 16 compactor passes. Therefore the optimum compactor pass is 16 and the improvement mechanism of impact compaction is change in loess microstructure and increase of micropores.