Case Study of a Collapse Investigation of Loess Sites Covered by Very Thick Loess–Paleosol Interbedded Strata

Deng, Longsheng; Fan, Wen; Yin, Yueping; Cao, Yanbo

doi:10.1061/(asce)gm.1943-5622.0001160

Cited by 28 publications

(6 citation statements)

References 31 publications

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“…Then have conducted research the combines microscopic experiments with macroscopic physical and mechanical experiments, leading to fruitful results. These results could provide a reference basis for multi-scale analysis of loess disasters [13][14][15][16][17][18][19][20][21][22][23][24]. In his research on the permeability properties of unsaturated loess, Wang Haiman assessed the permeability of densely packed loess and examined the microstructure changes in loess before and after rainfall using SEM and NMR methods.…”

Section: Introductionmentioning

confidence: 99%

Quantitative characterization of microstructure and research on spatial variation characteristics of loess of different strata in Luochuan, Shaanxi, China

Chang,

Yuan

2024

PLoS ONE

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The complete sequence of loess strata in Luochuan has become a typical section in loess strata, and is the main focus of research for many scholars studying loess. We were based on the theory of aeolian loess and established a set of quantitative index parameters for loess microstructure through our previous research, such as equivalent diameter, sphericity, morphology ratio, orientation angle Phi, orientation angle Theta, pore Eq-Radius, throat Eq-Radius and throat channelLength. Through the quantitative characterization of various index parameters of the Luochuan loess, we found that the probability density of each index parameter meets a specific distribution well, and in terms of spatial dimension, it shows that as the depth of the strata increases, the average particle size and the mode of pore Eq-Radius, throat Eq-Radius and throat channelLength generally increase, while the mode of particle morphology ratio generally decreases. In addition, loess particles in deeper strata are less prone to vertical sedimentation and tend to deposit gently or horizontally. Most particles in different strata are distributed in a northwest or southwest direction. During the formation period of strata, the main cause for spatial differences is the material carrying force. We conducted a statistical analysis on the correlation between the macroscopic physical properties of loess and its microstructure index parameters. Specifically, we found a positive correlation between loess density and the average particle size and the mode of particle equivalent diameter, Additionally, we found a negative correlation between loess liquid limit and plastic limit, and the mode of particle morphology ratio. Furthermore, there was a negative correlation between permeability coefficient and the mode of pore Eq-Radius, throat Eq-Radius, and throat channelLength.

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Section: Introductionmentioning

confidence: 99%

Quantitative characterization of microstructure and research on spatial variation characteristics of loess of different strata in Luochuan, Shaanxi, China

Chang,

Yuan

2024

PLoS ONE

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“…Several laboratory tests and field tests for common physical and mechanical indexes of loess have been conducted [7,8], and the collapsible behavior of loess was studied by analyzing the composition and mechanical properties [9,10], which contributed to the knowledge of collapsible characteristics. Nevertheless, the stress state and path of the loess sample taken in the laboratory tests are different from the actual state in the stratum, resulting in the collapse type and settlement amount of loess determined by the calculated value being distinct from the field immersion experiments, which were carried out for numerous projects [11][12][13][14] to directly obtain the water diffusion range and the cumulative settlement of the site loess, with favorable accuracy and reliability.…”

Section: Introductionmentioning

confidence: 99%

Collapsibility Mechanisms and Water Diffusion Morphologies of Loess in Weibei Area

Zhang

Zhao

2023

Sustainability

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A large-scale immersion experiment was carried out to assess the collapsibility characteristics of loess in Bu Li village located in the Weibei Loess Tableland, and the seepage characteristics and collapsibility evolution of loess were determined. The effects of void ratio, natural moisture content, material composition, and microstructure evolution on the loess collapsibility were characterized by X-ray diffraction, scanning electron microscopy, and water-soluble salt analysis to elucidate the collapsibility mechanisms. The water diffusion morphologies considering various foundation lithologies, initial water contents, and stratum combinations were studied with the numerical simulation method, and an inverted-box-shape barrier measure preventing loess from the water immersion was proposed. The results showed that the maximum consolidation settlement was approximately 380.5 mm for the test site, and the expansion of clay minerals and the dissolution of soluble salts during wetting were the critical reasons for loess collapse. The void ratio and natural moisture content showed a positive and negative correlation with the collapsibility coefficient, respectively, and the concept of collapsibility potential was introduced. The water diffusion morphologies in distinct stratum combinations significantly depended on the permeability capacity of the lower soil layer, and the optimal depths of the vertical barrier were recommended to be set at the maximum inflection point in the diffusion morphology or the main action layer.

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“…Loess is mainly distributed in the northwest region of China known as the Loess Plateau [1][2][3]. This plateau is situated in arid and semi-arid climatic zones, and has experienced intensive and large-scale irrigation activities that have led to numerous geological disasters like landslides and subsidence [4][5][6][7]. Heifangtai in Gansu Province serves as a resettlement area for the Liujiaxia Reservoir, and has experienced frequent loess landslides due to large-scale agricultural irrigation.…”

Section: Introductionmentioning

confidence: 99%

Effects of Sample Preparation Methods on Permeability and Microstructure of Remolded Loess

Ma,

Qiu,

Gao

et al. 2023

Water

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To explore the influence of sample preparation methods on the permeability and microstructure of remolded loess, remolded loess collected from Heifangtai was taken as the research object. A total of 40 sets of falling-head permeability tests were conducted using two commonly used sample preparation methods, and five different dry density and four initial water content conditions. Additionally, the electrical conductivity of the leachate and the microscopic structure of the samples were analyzed. The results demonstrate that compared to the transfer wetting method, the homogeneity of samples prepared using the pre-wetting method is inferior. This difference is particularly evident when the initial water content is high. Due to the long duration of the permeability test, the pore structure is prone to change, resulting in relatively higher permeability coefficients. Moreover, the total dissolved solids (TDS) of the leachate exhibit a significant decrease with increasing seepage time, indicating the loss of soluble salts. Microscopic structural analysis reveals that samples prepared using the pre-wetting method exhibit a greater number of large pores and aggregates, which are intrinsic factors contributing to the observed differences in permeability between the two sample preparation methods. Furthermore, it should be noted that the impact of the sample preparation method on the permeability of remolded loess is more significant when the dry density is relatively low (specifically, less than 1.45 g/cm3). Conversely, when the dry density is higher, the influence becomes less pronounced.

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Case Study of a Collapse Investigation of Loess Sites Covered by Very Thick Loess–Paleosol Interbedded Strata

Cited by 28 publications

References 31 publications

Quantitative characterization of microstructure and research on spatial variation characteristics of loess of different strata in Luochuan, Shaanxi, China

Quantitative characterization of microstructure and research on spatial variation characteristics of loess of different strata in Luochuan, Shaanxi, China

Collapsibility Mechanisms and Water Diffusion Morphologies of Loess in Weibei Area

Effects of Sample Preparation Methods on Permeability and Microstructure of Remolded Loess

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