Characterization and evolution of three-dimensional microstructure of Malan loess

Wei, Ya-ni; Fan, Wen; Yu, Bo; Deng, Longsheng; Wei, Tingting

doi:10.1016/j.catena.2020.104585

Cited by 94 publications

(34 citation statements)

References 39 publications

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“…e change in resistivity of compacted loess with water content and dry density can be attributed to the "water connectivity effect" and "compaction effect," which is essentially a reflection of the soil microstructure characteristics. At the same time, soil microstructure is precisely the main factor that affects loess collapsibility [29,30], and collapsibility is the external macroscopic manifestation of loess microstructure changes [31]. erefore, in theory, it is feasible to use the resistivity of loess to describe the size and variation of the collapsibility coefficient.…”

Section: Correlation Between the Loess Collapsibility Coefficient And Resistivitymentioning

confidence: 99%

Evaluation of Collapsibility of Compacted Loess Based on Resistivity Index

Nie

Wang

et al. 2021

Advances in Materials Science and Engineering

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Recently, a lot of engineering constructions have been carried out in the Loess Plateau of China. However, the collapsibility of compacted loess as a filler poses a potential threat to the safety and stability of buildings. To address this threat, the scientific evaluation of the collapsibility of compacted loess has become a key to engineering construction. This study, therefore, tested the resistivity of compacted loess under varying conditions of water content, dry density, and its collapsibility coefficient under a pressure of 200 kPa. The correlation between collapsibility and electrical parameters was determined, and based on the resistivity, a new method to evaluate the collapsibility of the compacted loess is proposed. The results show that the resistivity of compacted loess decreases with an increase in water content and dry density and that the effect of water content is more significant. There is a critical water content value that causes the resistivity decay rate to slow down. The collapsibility coefficient also decreases with an increase in water content and dry density, and under the same dry density or same water content, the collapsibility coefficient and resistivity are positively correlated. According to the normalized resistivity value ρ / ρ w , the relative collapsibility coefficient δ s /0.015, and the water content ω obtained in the experiment, a collapsibility coefficient prediction model based on the resistivity of compacted loess was established. Using resistivity to evaluate the collapsibility of loess is nondestructive and provides a new method to accurately and quickly evaluate the collapsibility of compacted loess.

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Section: Correlation Between the Loess Collapsibility Coefficient And Resistivitymentioning

confidence: 99%

Evaluation of Collapsibility of Compacted Loess Based on Resistivity Index

Nie

Wang

et al. 2021

Advances in Materials Science and Engineering

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“…There are many studies on the classification of pores in loess at home and abroad [40][41][42][43], but there is still no unified conclusion. In this study, we divided pores into four groups according to the PSD characteristics (Figure 12): Macropores (pore diameter >20 µm), mesopores (4-20 µm), small pores (0.1-4 µm), and micropores (<0.1 µm).…”

Section: Analysis Of Microstructural Characteristicsmentioning

confidence: 99%

Farming Influence on Physical-Mechanical Properties and Microstructural Characteristics of Backfilled Loess Farmland in Yan’an, China

Zheng

et al. 2020

Sustainability

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A gigantic project named Gully Land Consolidation (GLC) was launched in the hill-gully region of the Chinese Loess Plateau in 2011 to cope with land degradation and create new farmlands for cultivation. However, as a particular kind of remolded loess, the newly created and backfilled farmland may bring new engineering and environmental problems because the soil structure was disturbed and destroyed. In this study, current situations and characteristics of GLC are introduced. Test results show that physical-mechanical properties and microstructural characteristics of backfilled loess of one-year and five-year farmland are significantly affected by the Gully Land Consolidation project. Compared to natural loess, the moisture content, density, and internal friction angle of backfilled loess increase. On the contrary, the porosity, plasticity index, particle size index, and cohesion index decrease. Through SEM tests, it is observed that the particles of backfilled loess are rounded, with large pores filled with crushed fine particles, which results in skeleton strength weakness among particles and pores. The pore size distribution (PSD) of the four types of loess (Q3 loess, Q2 loess, one-year farmland, and five-year farmland) was measured using mercury intrusion porosimetry (MIP) tests, showing that the pore size of Q3 loess is mainly mesopores 4000–20,000 nm in size, accounting for 67.5%. The Q2, five-year, and one-year farmland loess have mainly small pores 100–4000 nm in size, accounting for 52.5%, 51.7%, and 71.7%, respectively. The microscopic analysis shows that backfill action degrades the macropores and mesopores into small pores and micropores, leading to weak connection strength among soil particles, which further affects the physical-mechanical properties of loess. The disturbance of backfilled loess leads to an obvious decrease in cohesion and a slight increase in internal friction compared to natural loess. The farming effect becomes prominent with increased backfill time, while the loess soil moisture content increases gradually. Both the cohesion and internal friction of the backfilled loess soil decrease to different degrees. This study is helpful to investigate sustainable land use in the Chinese Loess Plateau and similar areas.

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“…The in uences of pore structure on soil permeability have been quantitatively addressed (Ren and Santamarina 2018). The microstructure evolution of loess induced by water, loading and landslide has also been studied (Wei et al 2020;Zuo et al 2019;Yuan et al 2019). The characteristics of particles in loess are commonly utilized as indicators of the paleoclimatic environment (Sun et al 2018).…”

Section: Introductionmentioning

confidence: 99%

“…Numerous studies have adopted these methods to qualitatively investigate the microstructure of loess, including its particle, pore, and contact characteristics, and an increasing number of studies have quantitatively analyzed the loess microstructure in terms of size, shape, and arrangement, by combining these methods with image processing techniques (Deng et al 2020;Giménez et al 2012;Assallay 1998;Gao 1988). Recently researchers began to analyze the three-dimensional (3D) loess microstructure with the development of X-ray CT that can provide nondestructive testing (Li and Shao 2020; Yu et al 2020;Wei et al 2020;Li et al 2019;Wei et al 2019;Li et al 2018). However, great efforts are still required, especially in the aspect of 3D quantitative study of loess microstructure.…”

Section: Introductionmentioning

confidence: 99%

“…However, most of the previous works on loess microstructure by CT were conducted at resolution of dozens of micrometers, which are insu cient to identify particles. Recently, a limited number of studies investigated the microstructure of loess at particle resolution by using X-ray micro-computed tomography (Yu et al 2020;Wei et al 2020;Wei et al 2019). Nevertheless, a systematic analysis of the loess microstructure at the micrometer scale is still rare.…”

Section: Introductionmentioning

confidence: 99%

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Quantitative Study of Loess Microstructure At Micrometer Scale Via X-Ray Computed Tomography

Yuan¹,

Fan²

2021

Preprint

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The macroscopic properties of loess are significantly controlled by its microstructure. Quantitative analysis of loess microstructure is essential for modeling the microstructure and further incorporating the microstructural effects into geotechnical practice. However, loess has a multi-scale microstructure ranging from nanometer to millimeter scales, and researches at the particle resolution are still inadequate. This study systematically investigates the micrometer-scale microstructure of loess from Jingyang, China, via X-ray computed tomography and the image segmentation method that was explored for loess. The statistical analyses of three-dimensional (3D) microstructure reveal that the particle size follows the Weibull distribution, and the distributions of pore and pore throat sizes obey the gamma distribution. Most particles are blade-shaped, with a peak length ratio of (1.53–1.64):1.28:1. The particles are oriented in the polar directions but not azimuthally, in a spherical coordinate system, exhibiting a transversely isotropic structure. The quantitative microstructures of the loess and paleosol samples were slightly different irrespective of the large aggregates developed in paleosol sample. Moreover, the representative elementary volume obtained through porosity is also applicable for the analysis of microstructural parameters such as size distribution, shape factor, orientation angle, and pore connectivity. Besides, the two-dimensional (2D) distributions of the particle, pore, and pore throat sizes agree with the 3D distributions, except that the former were marginally smaller. However, the 2D sectional analysis of shape, arrangement, and pore connectivity cannot adequately represent the 3D characteristics.

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Characterization and evolution of three-dimensional microstructure of Malan loess

Cited by 94 publications

References 39 publications

Evaluation of Collapsibility of Compacted Loess Based on Resistivity Index

Evaluation of Collapsibility of Compacted Loess Based on Resistivity Index

Farming Influence on Physical-Mechanical Properties and Microstructural Characteristics of Backfilled Loess Farmland in Yan’an, China

Quantitative Study of Loess Microstructure At Micrometer Scale Via X-Ray Computed Tomography

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