The consequences of changes in the structure of loess as a result of cyclic freezing and thawing

Ye, Wanjun; Li, Changqing

doi:10.1007/s10064-018-1252-3

Cited by 42 publications

(22 citation statements)

References 3 publications

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“…Existing engineering experience shows that there are some imperfections in normal vegetation concrete such as high density, low permeability, insufficient nutrient retention ability, and so on. However, a too loose structure can easily lead to an obvious decrease in mechanical property and nutrient retention ability 41 , which is disadvantageous for plant growth and the self-stability of vegetation on the slope. Therefore, activated carbon, of which the structure is porous and ionic adsorption ability is strong, was chosen to be mixed in vegetation concrete in this research.…”

Section: Discussionmentioning

confidence: 99%

Effects of two types of activated carbon on the properties of vegetation concrete and Cynodon dactylon growth

Gao

Liu

et al. 2020

Sci Rep

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Vegetation concrete is one of the most widely used substrates for slope ecological protection in China. However, there are still some imperfections that are disadvantageous for plant growth, such as high density, low porosity, insufficient nutrient retention ability and so on. In this paper, the effect of wood activated carbon and mineral activated carbon on the physicochemical properties of vegetation concrete is studied. The experimental results show that the activated carbon proportion in vegetation concrete is positively related to the porosity, permeability coefficient, water holding capacity, and nutrient content and retention ability, while it is negatively related to the dry density, water retention ability, cohesive force and internal friction angle. However, it should be noticed that when the proportion exceeds 2%, the average height, aboveground biomass and underground biomass of Cynodon dactylon decrease with increasing proportion of activated carbon. The effect of wood activated carbon is generally more remarkable than that of mineral activated carbon. In addition, according to the research results, the effect of activated carbon on vegetation concrete can last for at least half a year, although it does slowly deteriorate with increasing time. By comprehensive consideration of the current industry standard, previous research results and economical reasoning, the recommended type of activated carbon is wood, with a corresponding suitable proportion ranging between 1 and 2%.

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Section: Discussionmentioning

confidence: 99%

Effects of two types of activated carbon on the properties of vegetation concrete and Cynodon dactylon growth

Gao

Liu

et al. 2020

Sci Rep

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“…In cold regions, geological disasters caused by FTC occur frequently and their mechanical mechanisms have received extensive attention [20,21]. Practically, in freezing and thawing environments, the fundamental causes of change in the macroscopic mechanical properties of soil are changes to its microstructure [7,8,17].…”

Section: Introductionmentioning

confidence: 99%

“…erefore, the multiscale structural features of soils subjected to FTC have also received attention. Computed tomography (CT), scanning electron microscopy (SEM), mercury intrusion porosimetry (MIP), and other technologies have been widely applied to the microscopic characterization of soil and rock [17,20,21]. is has led to several scholars adopting a range of image processing methods to quantitatively study the microstructures of various soils [26,[28][29][30].…”

Section: Introductionmentioning

confidence: 99%

Shear Strength and Microstructure of Intact Loess Subjected to Freeze‐Thaw Cycling

Liu

Jing

2021

Advances in Materials Science and Engineering

Self Cite

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In the Loess Plateau, seasonal freeze and thaw cause great damage to the mechanical behavior and microstructure of soil, which leads to frequent geological disasters during winter and spring. To investigate the influence of freeze-thaw (FT) cycling (FTC) on the shear strength and microstructure of intact loess, triaxial shear, nuclear magnetic resonance, and scanning electron microscope tests were carried out on soil samples after target FT cycles. The results indicate that the FTC has limited changes to the soil stress-strain curve, but has a significant attenuation effect on the peak deviatoric stress. The peak deviatoric stress was attenuated by FTC but changed insignificantly after ten cycles. The cohesive force decays exponentially with the number of FT cycles, while the internal friction angle increases slightly. Moreover, under FTC, the T2 hydrogen spectra of soil samples showed a multimodal distribution, with the main peak appearing to have two obvious upward shifts that occurred at 6 and 10 FT cycles. Indeed, a depolarization phenomenon related to the directional frequency of soil particles was observed, and the mass fractal dimension of the pore network increased slightly. In an FT environment, the shear strength declines due to accumulated internal microstructural damage. These findings contribute to a better understanding of the response of loess to FTC and provide novel ideas for the prevention of frost damage in loess areas.

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“…Fan et al [4] found that with increasing freeze-thaw cycles, the static and dynamic mechanical properties of dried sandstone and saturated sandstone decreased, but the uniaxial compressive strength and dynamic strength of dried sandstone were greater than those of saturated sandstone, while its elastic modulus and dynamic energy absorption capacity were lower than those of saturated sandstone. Similarly, with increasing freeze-thaw cycles, the integrity of the loess sample decreased [5], which led to a decline in its bearing capacity. In addition, Xu et al [6,7] found that cohesion of the loess varied with the cycles of freeze and thaw until a residual value was reached while the internal friction angle has little change.…”

Section: Introductionmentioning

confidence: 99%

Field Test Study of the Artificial Ground‐Freezing Method Subsurface Excavation Construction of Watered Sandy Stratum in Collapsible Loess Area

Mei

Zhao

Wang

et al. 2020

Advances in Civil Engineering

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Saturated sandy stratum often makes tunnel excavation exceedingly difficult owing to its high water content. The artificial ground-freezing (AGF) method is an effective way to reduce the construction risks in such stratum; however, the AGF mechanism in the saturated sandy stratum of a collapsible loess area still lacks sufficient research. Based on field tests and numerical simulations, this study investigates the regularity of the temperature development, frost heave, and thaw subsidence distribution during the cross passage construction of a saturated sandy stratum in a collapsible loess area, using the AGF method. The results showed that the inward development rate of the frozen soil wall in the saturated sandy stratum was faster than its outward development rate. The gradient of the soil cooling curve was positively related to the longitudinal depth of the cross passage. The thickness of the frozen soil wall calculated by the slowest development rate of the frozen soil was conservative. The application of the pressure relief hole was beneficial to the release of the frost-heaving force and the control of the frost-heaving displacement. The pressure gauge pressure increase could be used as an identifier for the closure of a frozen soil wall. After excavation, the inner wall of the cross passage moved toward the inner space of the passage.

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The consequences of changes in the structure of loess as a result of cyclic freezing and thawing

Cited by 42 publications

References 3 publications

Effects of two types of activated carbon on the properties of vegetation concrete and Cynodon dactylon growth

Effects of two types of activated carbon on the properties of vegetation concrete and Cynodon dactylon growth

Shear Strength and Microstructure of Intact Loess Subjected to Freeze‐Thaw Cycling

Field Test Study of the Artificial Ground‐Freezing Method Subsurface Excavation Construction of Watered Sandy Stratum in Collapsible Loess Area

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