Destructuration of saturated natural loess: From experiments to constitutive modeling

Abstract

It has been well recognized that unsaturated natural loess shows significant volume contraction upon wetting due to its metastable internal structure. But the structural effect on stress–strain relationship of saturated natural (undisturbed) loess is much less explored. Few attempts have been made in proposing a constitutive model for saturated natural loess. This study presents both laboratory tests and constitutive modeling of a saturated natural loess, with special focus on the structural effect and evolution of structure damage during loading. Oedometer and drained triaxial compression tests have been carried out on undisturbed and remolded saturated loess samples. It is found that the natural soil structure has dramatic influence on mechanical behavior of loess, including the compressibility, dilatancy, and shear strength. Destructuration, which is the damage of soil structure with deformation, is observed in both oedometer and triaxial tests. A constitutive model is proposed for saturated loess based on the experimental observations. The model is established within the theoretical framework of subloading and superloading surface concepts. Destructuration of loess is assumed to be affected by both plastic volumetric and shear strain. A new method for determining the initial degree of structure is proposed. The model can reasonably predict the compression and shear behavior of both undisturbed and remolded saturated loess.

Experimental Study on the Influence of Soil Structure Index on Loess Permeability

“…e effects of water content and dry density on the permeability of loess were considered in the test. e dry density of the three specimens in RA was about 1.25 g/cm 3 , the dry density of the specimens in RB was about 1.35 g/cm 3 , and the dry density of the specimens in RC and RD was about 1.41 g/cm 3 and 1.61 g/ cm 3 , respectively. ree specimens with different water contents were included in each group, and the specimens were recorded as 1, 2, and 3, respectively.…”

“…is phenomenon occurs under different dry densities, as shown in Figure 5. In undisturbed soil samples, when the dry density is 1.25 g/cm 3 , the vertical permeability coefficient is between 3.5 × 10 −5 m/s and 3.9 × 10 −5 m/s, and the average value is 3.7 × 10 −5 m/s. When the dry density is about 1.35 g/cm 3 , the average permeability coefficient of the three samples is 1.9 × 10 −5 m/s, and when the dry density increases to about 1.60 g/cm 3 , the average value is 1.07 × 10 −5 m/s.…”

“…e dry density of group IA is about 1.25 g/cm 3 , that of group IB is about 1.35 g/cm 3 , and that of group IC and ID is 1.41 g/cm 3 and 1.6 g/cm 3 , respectively. In order to compare the effects of different water contents on the permeability of undisturbed loess, three samples in each group have different water contents, which are recorded as No.…”

“…is research result provides a new idea and method for the description of structural parameters. e study of Fu et al [3] shows that the natural soil structure has a significant impact on the compressibility, dilatancy, and shear strength of loess, and the constitutive model of saturated loess based on the test provides a new method for determining the initial degree of structure.…”

Experimental Study on Creep Characteristics of Saturated Q2 Loess

“…The regions covered by loess account for 6.31 × 10 5 km 2 (Dijkstra et al, 1994), where it serves as the primary building material, building environment, or the foundation for the infrastructure. Due to the unique genesis of loess (Liu et al, 1985;Zhang et al, 1989;An et al, 1998;Sun, 2005;Chen et al, 2019;Fu et al, 2021), it possesses particular characteristics in deformation, strength, and stability (Wang, 1982;Feng and Zheng, 1982;Zheng, 1982;Lei, 1987), and abundant studies have been carried out on loess in the world. Loess below the groundwater table has high water content and a degree of saturation greater than 85%.…”