酸性溶液对黄土结构改良的试验研究

Experimental study on evolution of loess structure using acid solutions

提出了黄土结构改良的概念,即将黄土的天然属性——湿陷性和震陷性看作不良属性,对这种不良属性的消除实质上是对黄土固有属性的优化。在此基础上,采用化学方法改良了黄土的结构,即利用酸能溶解碳酸钙的特性,迅速有效的破坏黄土内部的不良孔隙结构,并通过电镜扫描的观察,分析了在不同压力下,不同浓度的乙酸溶液对湿陷性黄土的结构改良情况。试验结果表明：低压下,由于乙酸的作用,黄土的结构得到了显著改善;高压下,由于压力已经破坏了黄土的孔隙结构,乙酸的作用效果并不明显。又通过饱和压缩试验和固结快剪试验验证了乙酸溶液对黄土结构的改良效果：在同等压力条件下,经过乙酸溶液处理过的黄土发生二次湿陷或多次湿陷的可能性和危害性都较小,并且具有较高的抗剪强度。最后,指出了这一研究成果在现实应用中的可能：在预浸水法中添加适量的乙酸可以显著改善处理效果;能够为被酸性废水污染的黄土上的岩土工程建设及相关研究提供有价值的参考。

The concept of loess structure improvement is put forward in this study. It refers to the concept that the collapsibility and seismic subsidence are poor engineering properties for loess, and their elimination is essentially the optimization or evolution of the loess intrinsic quality. On this basis, a chemical method to improve the loess structure is proposed, i.e., using acid to dissolve calcium carbonate to destroy the pore structure quickly and effectively. The structure evolution of collapsible loess under different pressures in different concentrations of acetic acid solution is observed and analyzed by the scanning electron microscope（SEM）. The tests results indicate that the structure of loess is improved due to the acetic acid under low pressures, while the effect of acetic acid is not obvious under high pressures because of the previous complete elimination of the pore structure. In addition, the saturated compression tests and consolidated quick shear tests are carried out to verify the effect of the evolution of loess structure treated with acetic acid. The results indicate that the loess treated with acetic acid has a smaller possibility and perniciousness of secondary or multiple collapse and a higher shear strength under the same pressures. Finally, two practical applications of this research are put forward. One is that, if adding some acetic acid, the construction effect of pre-soaking method can be notably improved. The other one is that the research results can provide valuable reference for the geotechnical engineering construction on the loess polluted by acidic waste water and other related special studies.