Strength Characteristics Of Loess Research Articles

Study on the structure and strength characteristics of loess under the action of sodium sulfate.

In recent years, with the increasing frequency of human engineering activities, the phenomenon of sodium sulfate erosion has been widely observed in the Loess Plateau. This not only leads to difficulties in land reclamation but also affects human health, posing a significant risk to the investment environment in the Northwest region of China. In this study, three types of loess were treated with sodium sulfate to prepare remolded soil samples with salt content levels of 0%, 0.5%, 1.0%, 1.5%, 2.0%, and 2.5%. Observations and tests were conducted at multiple scales. The results indicate significant differences in the structural characteristics of the three types of loess under the influence of sodium sulfate. The higher the salt content in the loess, the greater the degree of structural damage. Subsequently, macroscopic mechanical properties were determined through direct shear tests, and it was found that as the salt content in the loess increased, the strength decreased. The resulting macroscopic mechanical properties showed a strong correlation with the microstructural characteristics. This study provides valuable insights for soil and water conservation and geological disaster prevention in the Loess Plateau region.

Time-Dependence of the Mechanical Behavior of Loess after Dry-Wet Cycles

The structure, time-dependent mechanical deformation, and strength characteristics of loess, which is loose and porous with well-developed vertical joints, are greatly affected by the dry-wet cycles, which are attributed to periodic artificial irrigation, rainfall, and water evaporation. To better understand the creep characteristics of loess under the effect of dry-wet cycles, Q2 loess samples obtained from the South Jingyang County, China, were subjected to different dry-wet cycles (0, 5, 10, 15, 20) and sheared in triaxial creep tests. The experimental results revealed that: firstly, the maximum value of the deviatoric stress corresponding to creep failure gradually decreases with an increase in the dry-wet cycles. Secondly, the long-term strength of the loess after dry-wet cycles were obtained through the Isochronous Curve Method. It is found that the long-term strength and the number of dry-wet cycles showed an exponential decreasing relationship. In addition, the creep damage mechanism of loess due to dry-wet cycles is proposed. This study may provide the basis for understanding the mechanical behavior of the loess under the effect of dry-wet cycles, as well as guidelines for the prevention and prediction of loess landslide stability.

Effect of root orientation on the strength characteristics of loess in drained and undrained triaxial tests

Ecological engineering measures are gaining popularity in the control of mountain hazards, particularly in shallow landslides, in which plant roots improve the shear strength of shallow soil. To measure such improvement, a series of drained and undrained triaxial tests were performed to investigate the role of Cunninghamia R. Br roots in loess soil mechanical behavior collected from Longchi Forest Center, southwest China. The specimens were prepared by distributing roots in four (4) distinct spatial orientations types, i.e., Horizontal, Vertical, Horizontal-Vertical (grid), and Randomly mixed in the soil. All specimens were first fully saturated and subsequently sheared in compression tests under drained and undrained conditions. The test results are evaluated in terms of monotonic stress-strain behavior, volume change, development of excess pore water pressure, and critical state behavior. The results showed that the addition of roots increased the soil shear strength, provides additional resistance to volumetric deformations and increased the positive excess pore water pressure as compared to plain loess soil. The results also revealed that the mechanical response of the soil-root composite depends on the type of root orientation. The shear strength improved highest with horizontal-vertical (grid) root orientation in both drained and undrained conditions among four root orientations. In contrast, the horizontal root orientation showed the least shear strength improvement. Additionally, for the same root orientation type, the shear strength improvement was more pronounced in undrained conditions compared to drained conditions. The plain and soil-root composite shear strength parameters showed that the addition of roots increased the cohesion with little effect on the mobilized angle of friction in both drained and undrained conditions. The findings of this research will provide a strong baseline for developing a predictive constitutive model for soil–root composite.

Analysis of deformation and failure characteristics of undisturbed loess under three axis test

The water content has a very obvious influence on the deformation and strength characteristics of loess, which is related to the safety of geological environment. In this paper, the triaxial test of loess is carried out, and the deformation characteristics of the loess are studied. The strength characteristics of different loci are studied. The study shows that as the water content increases, the effective cohesion of loess decreases and the effective internal friction angle changes. The amplitude is not large, indicating that the water content only affects the effective cohesion of the loess and does not affect the effective internal friction angle. When the water content reaches a certain value, the effective cohesion is no longer reduced and remains stable. The corresponding moisture content corresponds to the plastic limit. The Mohr-Coulomb strength theory is suitable for fitting shear failure and bulging deformation. While Griffith The strength theory is more suitable for fitting the splitting failure, indicating that the strength theory suitable for different failure modes is different.

Experimental study of the shear strength of soil from the Heifangtai Platform of the Loess Plateau of China

Loess landslides induced by irrigation are common geological disasters in the Loess Plateau, China. Long-term watering decreases the matric suction and soil strength of loess, thus causing the frequent occurrence of landslides. Therefore, studying the strength characteristics of unsaturated loess is of great significance for knowing how such landslides occur and, a step further, preventing them. Undisturbed loess samples in Heifangtai Platform were collected to measure their soil water characteristic curves (SWCC) and a series of direct shear tests and triaxial shear tests were carried out with unsaturated loess. Moreover, the strength characteristics of the loess were discussed. The results showed that in the direct shear test, the cohesion (c) increased linearly with increasing matric suction whereas the suction internal friction angle (φb) was approximately constant. In the triaxial shear test, c increased nonlinearly with increasing matric suction. The value of φb was a constant when matric suction was 0–100 kPa, but decreased as matric suction increased within the range of 100–200 kPa. The effective stress parameter (χ) lay in the range from 0.5 to 0.8. When the matric suction was small, the shear strength calculated by Lu’s suction theory was almost the same as that obtained by Fredlund’s theory. With the increase of matric suction, the shear strength calculated by Fredlund’s theory gradually outperformed that of Lu’s suction theory. The shear strength calculated by the curve of moisture desorption was slightly larger than that of moisture absorption. The variation trends of strength parameters with matric suction under the two tests were similar. The effective internal friction angles obtained by the triaxial shear test are slightly larger than those by the direct shear test. The suction internal friction angle (φb) was approximately a constant and smaller than φ´. The φb obtained by the direct shear test was slightly larger than that obtained by the triaxial test. Lu’s theory can be used to evaluate the stability of unsaturated soils on some loess slopes with high soil moisture content.

Research on Physical-Mechanical Property of Reshaped Loess Contaminated by Acid

With the rapid development of process of industrialization in Inner Mongolia, the environmental pollution, such as phenomenon of regional acid rain is gradually increasing. The Quaternary loess spread widely in Inner Mongolia. The ecological environment must be affected the intrusion acid rain. Meanwhile the physical-mechanical properties of original loess also are significantly influenced by the acid rain. To investigate the influence of acid rain on the physical-mechanical properties of loess, a series of triaxial tests in laboratory are carried out. The results showed that changes of PH value has significant effect on the specific gravity of soil grain, the limit moisture content , maximum dry density, and strength characteristics of loess.

Experimental Study on Shear Strength Characteristics and Stress-Strain Relationship of Loess

This paper mainly concerns the non-linear strength characteristics of the loess. A series of consolidated undrained triaxial tests(CU test) and consolidated drained triaxial tests (CD test) of normal consolidation and over consolidation loess specimens are carried out by using the normal triaxial apparatus of strain control. The stress-strain relationship curves and strength characteristics of loess are investigated and analyzed. The results show that the stress-strain relationship obtained by CU tests appears strain softening, while the stress-strain relationship for CD tests appears strain hardening. Different failure modes have different stress-strain relationships. Furthermore, the results also show that the peak strength, residual strength and residual strength ratio change with the different confining pressure. Based on the triaxial shear tests of normal consolidated loess, the influences of over-consolidated loess on the stress-strain relationships and strength characteristic are discussed. Several conclusions obtained in this paper can be referenced for the loess experimental study.

Experimental Study on Dynamic Strength Characteristics of Loess with Consideration of Initial Conditions

Experimental Study on Dynamic Strength Characteristics of Loess with Consideration of Initial Conditions

Experimental Study on Dynamic Strength Characteristics of Loess with Consideration of Initial Conditions

Experimental Study on Dynamic Strength Characteristics of Loess with Consideration of Initial Conditions

Collapse and strength characteristics of loess in Thailand : Phien-wej, N; Pientong, T; Balasubramaniam, A S Engng GeolV32, N1/2, Feb 1992, P59–72

Collapse and strength characteristics of loess in Thailand : Phien-wej, N; Pientong, T; Balasubramaniam, A S Engng GeolV32, N1/2, Feb 1992, P59–72