冻融作用对土的微结构与强度特性的影响

Effect of freeze-thaw on microstructure and strength of soils

人工冻结法因安全性能好、污染程度低、经济效益高等优点得到了广泛的应用。而冻融作用可以改变土体水分相态,影响土体的结构性能。通过现场试验与室内试验,对比分析了冻结法施工前后土体的微结构特征及剪切强度、压缩性能,揭示原状土层的物理力学性质。结果表明,冻融后的土颗粒形态从片状转变为厚层集聚体状;不同的土层在冻融后黏聚力和内摩擦角均呈下降趋势,反映出土的抗剪强度的劣化;冰晶的增长促使土的孔隙率增大,造成土体软化使得其压缩性得到增强;静力触探过程中的锥尖阻力和侧摩阻力在冻融后显著降低,波速变慢,论证了冻融作用导致土体强度减小、土体发生软化的现象。

Artificial freezing method has been widely used due to the advantages of safety,low pollution and high economic benefits.However,the freeze-thaw action can change the soil moisture phase state and affect the structural properties of the soil.In this paper,the microstructural characteristics of the soil before and after the construction of the freezing method are compared and analyzed through field and indoor tests.The shear strength and compression properties are also analyzed to reveal the physico-mechanical properties of the soil layer in its original state.The results show that the morphology of soil particles after freeze-thaw transformed from lamellar to thick-layered agglomerates.Different soil layers showed a decreasing trend in cohesion and internal friction angle after freeze-thaw,reflecting the deterioration of the shear strength of the soil.The growth of ice crystals contributed to the increase of the soil porosity,which resulted in the softening of the soil and enhanced its compressibility.Cone tip resistance and lateral friction resistance during static cone penetration tests significantly decreased and wave velocity slowed down after freeze-thawing.The results demonstrate that the freeze-thaw action leads to a reduction in the strength of the soil and softening of the soil.