The Dependence Between Shear Strength Parameters and Microstructure of Subgrade Soil in Seasonal Permafrost Area

Abstract

Permafrost and seasonal permafrost are widely distributed in China and all over the world. The failure of soil is mainly shear failure, and the strength of soil mainly refers to the shear strength. The two most important parameters of shear strength are cohesion and angle of internal friction. In order to ensure the sustainability of road construction in seasonal permafrost area, the microstructure of subgrade soil was observed and analyzed. First, three subgrade soils with different plasticity indices were prepared for triaxial test and scanning electron microscope (SEM). Then, these specimens underwent freezing–thawing (FT) cycles and were obtained shear strength parameters by triaxial shear test. Next, the microstructure images of soil were obtained by SEM, and the microstructure parameters of soil were extracted by image processing software. Finally, the correlation method was used to analyze the dependence between the shear strength parameters and the microstructure parameters. Results revealed that subgrade soils with a higher plasticity index had higher cohesion and lower angle of internal friction. In addition, with the increase of the number of FT cycles, the diameter and number of soil particles and pores tend to increase, while the roundness, fractal dimension and directional probabilistic entropy of particles decreased. With the increase of the plasticity index, the particle and pore diameter decreased, but the particle and pore number increased. Besides, particle roundness had the greatest influence on the cohesion and angle of internal friction of shear strength parameters.

Determination of the Shear Strength of Unsaturated Loess Samples from Conventional Triaxial Shear Tests Applying Rubber Membrane Correction

“…Information about these two parameters is required in the rational design of a sustainable geotechnical infrastructure considering stability aspects [1][2][3]. Triaxial shear testing equipment is widely used for determining the conventional shear strength parameters for saturated soils [4,5]. In a triaxial test, the specimen used for testing is wrapped with a rubber membrane to separate it from water (oil), which facilitates applying boundary stresses and controlling the drainage conditions to determine the drained or undrained shear strength of saturated soils [6].…”

Estimation of the Shear Strength of Sand-Clay Mixtures Based on the ANN and Low-Field NMR

“…However, the input variables of these ANN models for predicting the shear strength of soil mainly included the basic physical properties of soil such as the clay content, silt content, sand content, liquid limit, plastic limit, plastic index, water content, dry density, specific gravity, and void ratio [8,10,20,21]. The mechanical properties of soil are substantially affected by the pore characteristics [31,32]. These variables cannot directly reflect the pore characteristics of soil and need to be determined by other tests.…”

“…The characteristic variables of the T2 spectrum can be used to reflect the pore size distribution and water classification in porous media [33,34,43]. As mentioned above, the mechanical properties of soil are substantially affected by the pore characteristics [31,32]. The basic physical properties of soil cannot directly reflect the pore characteristics of soil.…”

Effect of the interlayer on soil temperature and the transformation between phreatic water and soil water under laboratory freeze-thaw action

“…Seasonal frozen soil areas are distributed widely throughout China, accounting for about 70% of the total land area. Most areas of seasonally frozen soil have cold and dry climates and poor water resources (Liu et al, 2020). The soil in frozen areas undergoes a complex freezing and thawing process in the winter and spring, including a series of physical and chemical activities, such as water migration, temperature change, salt movement, and a three-phase change of water (Hansson et al, 2004;Min et al, 2022).…”