Variations in strength and deformation of compacted loess exposed to wetting-drying and freeze-thaw cycles

Li, Guoyu; Wang, Fei; Ma, Wei; Fortier, Richard; Mu, Yanhu; Mao, Yuncheng; Hou, Xingsong

doi:10.1016/j.coldregions.2018.03.021

Cited by 121 publications

(39 citation statements)

References 33 publications

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“…Then, the relationship between the amount of porosity change and freeze-thaw damage can be obtained from Equations (11) and (12).…”

Section: =mentioning

confidence: 99%

“…Wang et al [10] studied the rate of change of loess volume before and after freeze-thaw by changing the blending ratio, in order to determine the reasonable ratio so that the loess can maintain its microstructure during the freeze-thaw cycle. Li et al [11] aimed at the strength degradation and structural degradation of compacted loess under the dual effects of wet and dry and freeze-thaw. Li et al [12] used nuclear magnetic resonance (NMR) technology to study the degradation characteristics of sandstone microstructure in freeze-thaw cycles, and used fractal theory to calculate the fractal dimension of rock pore development after different freeze-thaw cycles.…”

Section: Introductionmentioning

confidence: 99%

“…Testing the strength of freeze-thaw cycle loess is of great importance for evaluating the stability of slopes and foundations in loess areas. In order to explore the changes of mechanical properties of loess under the action of freeze-thaw cycles, it is found that the change of water content and the rate of freezing have a great influence on the strength change [9,11,14]. Yan et al [15] studied the unconfined compressive strength and pore distribution characteristics of lime fly ash loess through a series of experiments under freeze-thaw cycles.…”

Section: Introductionmentioning

confidence: 99%

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The Influence of Regional Freeze–Thaw Cycles on Loess Landslides: Analysis of Strength Deterioration of Loess with Changes in Pore Structure

Yang

Liu

2020

Water

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The loess landslide in Gaoling District of Xi’an, Shaanxi in China is closely related to the seasonal freeze–thaw cycle, which is manifested by the destruction of pore structure and strength deterioration of the loess body under freeze–thaw conditions. In order to study the relationship between macro-strength damage and pore structure deterioration of saturated loess under freeze–thaw conditions and its influence on the stability of landslides, this paper explores the effect of freeze–thaw cycles on the strength of saturated undisturbed loess through triaxial compression test, and explores the micro-microstructure changes of saturated undisturbed loess through scanning electron microscopy (SEM) and nuclear magnetic resonance (NMR). This is to analyze the evolution of the pore structure and strength loss evolution of saturated loess during the freeze–thaw process, and to describe the freeze–thaw damage of saturated undisturbed loess through the change of porosity and strength deterioration. Then, the internal correlation expression between the porosity change and the strength degradation is established to realize the verification analysis of the test data based on the correlation model. The research results show that: (1) As the number of freeze–thaw cycles increases, the peak strength loss rate gradually increases, and the strength deterioration of saturated loess becomes more and more obvious. (2) The freeze–thaw cycle will lead to the development of pores and cracks in the sample, accompanied by the generation of new cracks, which will cause the deterioration of the pore structure of the sample as a whole. (3) The response of strength damage and porosity deterioration of saturated undisturbed loess is roughly similar under the freeze–thaw cycle. The change in porosity can be measured to better reflect the strength deterioration of saturated loess. Therefore, the change of pore structure of undisturbed loess under freeze–thaw cycle conditions is tested by field sampling and indoor tests to reflect the phenomenon of strength deterioration, thereby analyzing the stability of loess slopes.

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“…Then, the relationship between the amount of porosity change and freeze-thaw damage can be obtained from Equations (11) and (12).…”

Section: =mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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The Influence of Regional Freeze–Thaw Cycles on Loess Landslides: Analysis of Strength Deterioration of Loess with Changes in Pore Structure

Yang

Liu

2020

Water

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“…However, variable rainfall intensity, changes in groundwater, and surface evaporation in the Loess Plateau created a regular dry-moist cycle in local soils. These climatic changes cause the drying-wetting cycles to occur under natural conditions, which affects soil hydraulic properties (Kong et al 2017) and shear strength (Li et al 2018), important factors which influence the fill and loess slope stability.…”

Section: Introductionmentioning

confidence: 99%

The Influence of Drying-Wetting Cycles on the Suction Stress of Compacted Loess and the associated Microscopic Mechanism

Nie¹,

Ni²,

Li³

et al. 2021

Preprint

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In order to better understand and analyze the unsaturated stability of loess fillings, it is necessary to study the changes in suction stress before and after the drying-wetting cycles. In this study, the soil-water characteristic curve (SWCC) of compacted loess before and after drying-wetting cycles was tested using the filter paper method. Then, the suction stress was calculated and the microstructure of the loess sample was determined by the scanning electron microscope（SEM）and nuclear magnetic resonance (NMR). The results showed that the drying-wetting cycles had an important influence on the suction stress characteristic curve (SSCC) and microstructure of compacted loess. The change in suction stress before and after the drying-wetting cycles can be explained by the loess microstructure. The drying-wetting cycles did not significantly change the basic trend of the compacted loess's suction stress, but it increased the porosity and the diameter of the dominant pore (i.e., the inter-aggregate pore) of the sample, and reduced the suction stress when the same matrix suction was applied. The main significant change in suction stress with matrix suction occurred within the range of the dominant soil pores. The larger the diameter of the dominant pore, the smaller the suction stress under the same matrix suction. In addition, this study also proposes a new method for calculating suction stress based on the pore size distribution（PSD） parameters, which is more convenient than traditional calculation methods based on SWCC parameters.

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“…Slope instability in permafrost regions is closely related to the freeze-thaw cycle. The decrease in the shear strength of the slope after freezing and thawing is the main reason for the failure of the slope [4,5]. The effect of freezing water retention can reduce the stability of loess slopes in seasonal frozen soil areas by about 25% [6].…”

Section: Introductionmentioning

confidence: 99%

Effect of Freeze-Thaw on the Stability of a Cutting Slope in a High-Latitude and Low-Altitude Permafrost Region

Zhao

Wang

2020

ASI

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In order to study the influence of freeze–thaw cycles on the stability of cutting slopes in high-latitude and low-altitude permafrost regions, we selected a cutting slope (the K105+700–800 section of National Highway 332) in the Elunchun Autonomous Banner in Inner Mongolia as the research object. Located in the Greater Xing’an Mountains, the permafrost in the Elunchun Autonomous Banner is a high-latitude and low-altitude permafrost. The area is also dominated by island-shaped permafrost, which increases the difficulty of dealing with cutting slopes, due to its morphological complexity. Surface collapse, caused by freeze–thaw erosion in this area, is the main reason for the instability of the cutting slope. Indoor freeze–thaw tests, field monitoring, and an ABAQUS numerical simulation model were conducted so as to quantify the decrease in rock strength and slope stability under freeze–thaw conditions. The following conclusions were drawn. (1) As the number of freeze–thaw cycles increased, the compressive strength of the rock specimens obtained from this slope gradually decreased. After 50 freeze–thaw cycles, the uniaxial compressive strength measured by the test decreased from 40 MPa to 12 MPa, a decrease of 37%. The elastic modulus value was reduced by 47%. (2) The safety factor of the slope—calculated by the strength reduction method under the dynamic analysis of coupled heat, moisture, and stress—gradually decreased. After 50 freeze–thaw cycles, the safety factor of the slope was only 0.74. (3) Reasonably reducing the number of freeze–thaw cycles, reducing the water content of the slope, slowing down the slope, and increasing the number of grading steps can effectively improve the stability of the slope. The results of this study can provide a reference for the design and stability analysis of slopes in permafrost regions of the Greater Xing’an Mountains.

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Variations in strength and deformation of compacted loess exposed to wetting-drying and freeze-thaw cycles

Cited by 121 publications

References 33 publications

The Influence of Regional Freeze–Thaw Cycles on Loess Landslides: Analysis of Strength Deterioration of Loess with Changes in Pore Structure

The Influence of Regional Freeze–Thaw Cycles on Loess Landslides: Analysis of Strength Deterioration of Loess with Changes in Pore Structure

The Influence of Drying-Wetting Cycles on the Suction Stress of Compacted Loess and the associated Microscopic Mechanism

Effect of Freeze-Thaw on the Stability of a Cutting Slope in a High-Latitude and Low-Altitude Permafrost Region

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