Effects of Salt Content on Shear Properties and Microstructure of Stabilized Sulphate Saline Soil
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摘要: 因蒸发和毛细作用,西北地区硫酸盐渍土中的盐结晶积聚在表层;盐颗粒弱化了土的结构稳定性,导致土的抗剪性能下降。以石灰固化0.3%~5%含盐量的土为例,开展三轴压缩试验与扫描电镜观察,研究含盐量对固化土抗剪性能与微观结构的影响。结果表明:随着含盐量增加,固化土的抗剪强度先增大后减小,1.5%含盐量的土达到峰值,这得益于盐颗粒填充孔隙与盐胶结的共同作用;对1.5%~3%含盐量的土,过多的盐颗粒使得盐胀作用占据优势,土样出现少量微裂纹,此时土的黏聚力与内摩擦角均下降;超过3%含盐量的土,盐胀作用尤为强烈,土样微裂纹较多,已无法用于三轴压缩试验。工程建设中,对小于1.5%含盐量的土可使用石灰固化;为保持土的含盐量不再变化,宜采取防止水分蒸发与盐分积聚的工程措施。Abstract: Due to evaporation and capillarity effetcs, salt crystallizes and accumulates in the surface layer of soils in northwest China. The salt particles weaken the stability of the soil and lead to the decline of the shear resistance. Triaxial compression tests and SEM tests were carried out to study the effects of salt content on the shear properties and microstructure of the stabilized saline soil with a salt content of 0.3%-5%. With the increase of salt content, the shear strength first increasesd and then decreased, reaching its peak at 1.5% salt content, which was due to the combined effect of salt particles filling the pores and salt cementation. For the saline soil with a salt content of 1.5%-3%, excessive salt particles played a major role in salt swelling, and a few micro-cracks appeared in the soil sample. At this time, the cohesion and internal friction angle of the saline soil decreased. The saline soil with a salt content exceeding 3% exhibited a strong salt swelling effect, and there were many micro-cracks in the soil sample, making it impossible to conduct triaxial compression tests. The saline soil with a salt content below 1.5% can be stabilized by lime in engineering. In order to prevent the salt content of the soil from increasing, engineering measures should be taken to control evaporation and salt accumulation.
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