基于核磁共振和扫描电镜的蒙内铁路膨胀土改良细观结构研究

Modified mesostructure of Standard Gange Railway expansive soils of Mombasa-Nairobi based on nuclear magnetic resonance and scanning electron microscope

孔隙结构及分布特征对膨胀土的物理力学性质有重要影响。通过核磁共振技术,对石灰–火山灰改良处理前后的膨胀土孔隙特征进行分析,获得膨胀土孔隙变化及分布规律。通过SEM对细观结构生成高分辨率图像,分析改性前后膨胀土内部颗粒胶结方式变化。试验结果表明:改良后直径在0~0.1μm范围内的孔隙个数明显减少,直径在0.1~4μm范围内的孔隙个数有所增加,直径超过4μm的孔隙个数整体上呈减小趋势。膨胀土进行改性处理后,形成具有蜂窝状、骨架状、海绵状的混合结构,提高了土颗粒的胶结紧密程度,降低了孔隙的连通性,有效抑制了膨胀土的胀缩特性。

The pore structure and distribution characteristics have important influences on the physical and mechanical properties of expansive soils. The pore characteristics of the expansive soils before and after improvement treatment of lime-volcanic ash are analyzed using the NMR technology to obtain their change of pores and distribution laws. The change of internal cementation of the expansive soils before and after modification is analyzed by means of the scanning electron microscopy. The experimental results show that the number of pores in the range of 0~0.1 μm in diameter is significantly reduced, that in the range of 0.1~4 μm in diameter increases, and that in diameter more than 4 μm decreases as a whole. After modification of the expansive soils, a mixed structure with honeycomb structure, skeleton structure and spongy structure is formed, which improves the compactness of soil particles, reduces the connectivity of pores, and effectively inhibites the swelling and shrinkage characteristics of the expansive soils.