关键词: 古土壤细微观结构; 冻融循环; 扫描电镜; 三轴试验; 核磁共振;

Abstract: In order to study the microstructural changes of landslides paleosoil subjected to freeze-thaw cycling process and their correlation with macro-mechanical properties, this paper conducted a large number of conventional triaxial tests in macroscopic view and scanning electron microscopy and nuclear magnetic resonancein microscopic view.The results show that from macroscopic aspect, as the number of freeze-thaw cycles increases, the stress-strain curve changes from softening type to hardening type and the soil shear strength decreases under the same moisture content, which means that the freeze-thaw cycle causes deterioration of the loess structure and reduction of shear strength.And with the increase of moisture content, the failure deviation stress will increase slowly in a certain degree.From microscopic aspects, the particles develop, and the particle contact forms are mainly surface-to-surface contact and surface-to-edge contact, and micro-pores distributes intensively accounting for a large proportion.As the number of freeze-thaw cycles increases, the average shape coefficient of the pore decreases firstly and then increases, while the fractal dimension of the morphological distribution continues to increase and tends to stabilize after 15 freeze-thaw cycles.On microscopic view, the main peak of the T2 spectrum curve occupies most of the curve, and as the number of freeze-thaw cycles increases, the T2 peak curve decreases significantly with a small increase in the curve width and a gradual decrease in the peak area, and the peak of the initial freeze-thaw cycle decreases the most, indicating that the initial cycle changes the soil structure significantly.

Key words: microstructure of paleosoil; freeze-thaw cycle; scanning electron microscope; triaxial test; nuclear magnetic resonance;