石灰粉煤灰固化天津滨海软土试验研究

天津滨海新区大面积分布的海积软土含水量高、孔隙比大、强度较低,对工程的安全建设和使用存在很大影响,在工程实践中常需要进行固化处理。本文以石灰粉煤灰为固化材料,通过大量室内试验,以及微观结构测试,研究其对天津滨海软土的改良效果。室内试验结果表明,二灰土各项力学性质明显提高,即压缩性降低,水稳性良好,无侧限抗压峰值应变及三轴峰值应变较小,由于其强度很大程度依赖于土体颗粒间的胶结作用,一旦破坏,二次抗压强度则较低。微观结构测试分析表明,石灰粉煤灰与软土在拌合均匀状态下,经一系列物理化学作用,土体颗粒胶结成土团粒,粒间孔隙也得到填充。随着龄期的增长,二灰土孔隙数量减少,等效直径减小,土体颗粒数量减少,等效直径增大;而随着压力的增大,二灰土表现出孔隙数量增多而孔隙等效直径减小,颗粒数量和等效直径变化较小的趋势。室内试验与微观测试认为石灰粉煤灰可用于固化天津滨海软土,是一种经济合理的固化剂。

Experimental Study on Lime-fly Ash to Cure Tianjin Marine Soft Soil

The marine soft soil in Tianjin coastal region has properties of high water content, high porosity and low strength. It can’t meet the needs of engineering construction and has to be improved. The solidification effect of the lime-fly ash was studied based on a large number of indoor tests, as well as the microstructure test. The results of the laboratory test show that the mechanical properties of the lime-ash soil can be enhanced distinctly as the compressibility gets reduced, the water stability gets better and the peak strains of the triaxial stress-strain curve and the unconfined compression stress-strain curve in axial direction get smaller. After being destroyed and getting maintained again, the compressive strength gets lower for the cementation which contributes the most to the strength of the lime-ash soil is damaged. Microstructural analysis shows that the cementation makes clay particles as soil granular and fills the intergranular pore. With the growing of the age, the amount of the pore and particle decreases, so as to the equivalent diameter of pores, but the equivalent diameter of particles increases. With the growing of the pressure, the amount of the macropore decreases but the equivalent diameter of the pore increases, while the amount and the equivalent diameter of the particles remain stable. Therefore, the lime-fly ash is fit to be used in solidifying the soft soil in Tianjin coastal region and is an economic and reasonable solidification agent.