Study of loess pore structure characteristics based on CT scanning

Abstract

Porosity is one of the important characteristics reflecting the microstructure of loess and directly affects the physical and mechanical properties of loess, such as water sensitivity, permeability and strength. To study the micropore structure characteristics of loess under hydraulic coupling, micro CT technology was used to scan the initial structure of natural undisturbed, undisturbed saturated and remolded loess and the soil structure after unconsolidated-undrained shear tests. The evolution characteristics of the pore structure before and after shear tests are analyzed through the three-dimensional structure model of loess. The results show that the pore structures of the natural undisturbed loess, the saturated undisturbed loess and the remolded loess are significantly different, and the pore structures of the samples have a significant impact on the shear failure process. The process of saturation and remodeling can reduce the macropores of undisturbed soil.Shear stress can cause shear failure of natural undisturbed and remolded loess, compression failure of undisturbed saturated loess, and the increases of local porosity. The natural undisturbed and undisturbed saturated loess show a large number of micropores and small pores before and after shear, and the pore dip angle is mainly distributed between 50°-90°, which explains the main reason for the formation of the metastable structure of loess. The remodeled loess has a uniform pore size distribution due to the disturbance effect, and the remodeled and saturated loess is more prone to buckling and yielding under hydraulic action. It is revealed that the microstructure of shear deformation and failure of loess is mainly manifested in the dissolution of intergranular cement, the collapse and filling of pores, and the rotation, fragmentation and slip of particles. The test results can provide a basis for the mechanism of shear strength reduction and collapsibility of loess.

Keywords

• loess shear
• pore structure
• ct test
• pore three dimensional model