酸雨作用下红黏土渗透性影响机制及压实度控制

Mechanism of permeability and control of compaction for red clay under the influence of acid rain

酸雨会溶解红黏土中的部分物质,是导致红黏土路基病害的重要因素。研究红黏土在酸雨环境下的渗透机制、提出红黏土路基压实度建议标准对于红黏土地区路基设计具有很强的工程实际意义。设计新型的淋溶仪器,用不同p H值溶液模拟酸雨对原状红黏土进行淋溶后,进行渗透性试验、物相分析试验及电镜微结构扫描试验,深入分析酸雨对桂林红黏土渗透性的影响因素及影响机制;进一步通过试验研究重塑红黏土渗透系数与压实度的变化关系。结果表明:红黏土渗透系数随干密度增大而减小;红黏土中的主要物质成分包括铁、硅、铝和钾4种金属元素的化合物均能被酸性物质溶解,随地下水迁移而流失,造成土体结构孔隙比增大、内部的孔隙连通性增强,酸雨的p H值越小,这些物质的溶解程度越大,对红黏土的渗透性影响越大;当在p H值≥3的酸雨地区用红黏土作为路基填料时,控制路基压实度≥95%可有效预防酸雨对红黏土的不利作用。

Acid rain will dissolve some of the material of red clay, which is the important factor of red clay roadbed diseases. The research on the penetration mechanism of red clay in acid environment and recommendation of subgrade compaction standards to red clay roadbed has a strong practical significance. Use simulated acid rain of different pH value the solution leaching undisturbed of red clay by designing new leaching equipment to conducting penetration test, phase analysis test and SEM experiments, to deeply analyze the impact of acid rain on the factors and mechanisms of Guilin red clay permeability. Further research on the relationship between changes in permeability and the degree of compaction of reshape red clay by the experimental study. The results show that： Red clay permeability decreases with increasing dry density. Chemical compounds of four metal elements（Fe, Si, A1, K）, which are the main compositions in laterite soil, all can be dissolved by acidic substances, and due to the dissolution caused by acid rain. The lower the pH value of acid rain, the greater the degree of dissolution of these substances, the greater the influence on permeability of laterite soil. When using red clay as roadbed filler in acid rain areas of pH value not less than 3, the degree of compaction not less than 95% could be controlled to prevent the adversely affect of acid rain on the laterite soil sub^rade effectively.