水玻璃固化硫酸盐渍土强度特性及固化机制研究

盐渍土化学固化法是解决盐渍土盐胀、溶陷和腐蚀等不良工程问题的有效方法之一。通过无侧限抗压强度试验、X射线衍射试验、化学成分分析和扫描电镜试验研究了石灰粉、煤灰、水玻璃联合固化硫酸盐渍土的强度特征，分析探讨了其固化机制。试验结果表明：石灰含量小于8%时，石灰、粉煤灰、水玻璃联合固化硫酸盐渍土的抗压和抗剪强度较石灰粉煤灰固化土有大幅度提升，固化土强度随水玻璃浓度几乎呈线性增长。水玻璃固化硫酸盐渍土强度增加的机制在于：水玻璃的碱激发粉煤灰作用和水玻璃与盐渍土中化学成分的吸附作用所生成各类凝胶的填充和包裹，使得骨架颗粒的接触面积增大，颗粒之间的孔隙逐步减小，骨架颗粒由点接触变为面接触，固化盐渍土通过凝胶而黏结成为一个紧密的空间网状整体结构，土体强度得以提高。同时，复杂的物理化学作用大幅度降低了固化盐渍土中 含量，有效地抑制了硫酸盐渍土的盐胀特性。

Strength characteristics and solidification mechanism of sulphate salty soil solidified with sodium silicate

Chemical consolidation is one of the most effective methods for solving the engineering problems of saline soil, such as salt expansion, collapse and erosion. Based on the unconfined compressive strength test, X-ray diffraction, chemical analysis and scanning electronmicroscope, the solidification mechanism and strength characteristics of the sulphate saline soil solidified by lime, fly ash and sodium silicate are analyzed. The results show that when the lime content is less than 8%, the compressive strength and shear strength of lime-reinforced soil, fly ash and sodium silicate are higher than those of the sulphate saline soil solidified by lime and fly ash; the strengths of the former grow almost linearly with the concentration of sodium silicate. The alkali-activated action on fly ash caused by sodium silicate and adsorption between sodium silicate and saline soil generate mass gels, leading to an increase in contact area between framework grains, a reduction in intergranular pore, and a transformation from point-contact to surface-contact. The grains of saline soil bond each other into 3D framework via gels, resulting in an increase in the strength of saline soil. Meanwhile, the salt expansion behavior of saline soil is also restrained effectively due to the sharp reduction in the content of induced by complex physicochemical reactions as saline soil is solidified.