Shear behavior and microstructural variation in loess from the Yan'an area, China

Nan, Jingjing; Peng, Jianbing; Zhu, Feng-ji; Ma, Penghui; Liu, Ru; Leng, Yanqiu; Meng, Zhenjiang

doi:10.1016/j.enggeo.2020.105964

Cited by 33 publications

(14 citation statements)

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“…The shear strength of loess is mainly composed of the cohesion (c) and the friction strength (σtanφ). (Li, 2018;Nan et al, 2021) found that the in uence of water on the shear strength of soil is mainly the in uence on the cohesion of soil rather than the internal friction angle. The reason is that the internal friction angle of loess is mainly affected by the internal factors such as soil density, particle grading, particle shape and mineral composition (Zhao, 1994).…”

Section: Moisture Content Effect On the Shear Strength Of Loessmentioning

confidence: 99%

Effect of moisture content on the time-dependent mechanical characteristics of loess

et al. 2022

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It is of great signi cance to study the time-dependent mechanical properties of loess, as loess landslides are closely related to them. The purpose of this study is to investigate the effect of moisture content on instantaneous and time-dependent deformation, strength and failure behaviors of undisturbed loess specimens from Nangou in Yan'an City, Shanxi Province, China, via triaxial shearing tests and multi-loading triaxial creep tests under moisture contents of 5%, 10%, 17% and 22%. The results show that the timedependent deformation of loess increase with the moisture content, while the time-dependent deformation rate decreases slowly. The soil deformation is divided into four stages based on the peak strain rate. Furthermore, the instantaneous and long-term strength of loess decrease with increasing moisture content, and the instantaneous strength decreases more than the long-term strength. The failure mode of undisturbed loess changes from shear failure to homogeneous failure with increasing moisture content; when the failure mode is shear failure, the thickness of the shear band that forms at the specimen surface over time is smaller than the corresponding thickness that forms instantaneously. Finally, the macroscopic morphology and microstructure of loess specimens were considered together to analyze the effect of moisture content on the instantaneous and long-term mechanical behavior of loess and to discuss the process of loess deformation to failure.

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Section: Moisture Content Effect On the Shear Strength Of Loessmentioning

confidence: 99%

Effect of moisture content on the time-dependent mechanical characteristics of loess

et al. 2022

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“…12b), which makes the loess structure reach a relatively stable state (elastoplastic deformation stage), the strength of soil is mainly provided by the friction between particles. According to the above analysis, the instantaneous shear process of loess can be regarded as the process of interparticle bond damage (e.g., particle slippage, particle structure collapse, and particle damage), particle recombination (e.g., compression, extrusion, and rearrangement) and nally the formation of a relatively stable structure (e.g., from an overhead structure system to an interlocked-cementation structure system) (Nan et al 2021;Taylor 1948;Wang 1997;Xu et al 2019) However, the variations in strength caused by interparticle bond damage and particle recombination are related to time under certain factors (e.g., the viscosity of a water lm around a solid particle in soil or the connection of soil particles) (Chen et al 2001;Вялов 1987), and the deformation of soil in the process of internal stress adjustment is time-dependent deformation. Figure 4h is taken as an example to analyze the generation and development of time-dependent strain in undisturbed loess.…”

Section: Analysis Of the Shearing Process Of Loessmentioning

confidence: 99%

Effect of Moisture Content On The Time-Dependent Mechanical Characteristics of Loess

Chen

Peng

Xie

et al. 2021

Preprint

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It is of great significance to study the time-dependent mechanical properties of loess, as loess landslides are closely related to them. The purpose of this study is to investigate the effect of moisture content on instantaneous and time-dependent deformation, strength and failure behaviors of undisturbed loess specimens from Nangou in Yan'an City, Shanxi Province, China, via triaxial shearing tests and multi-loading triaxial creep tests under moisture contents of 5%, 10%, 17% and 22%. The results show that the time-dependent deformation of loess increase with the moisture content, while the time-dependent deformation rate decreases slowly. The soil deformation is divided into four stages based on the peak strain rate. Furthermore, the instantaneous and long-term strength of loess decrease with increasing moisture content, and the instantaneous strength decreases more than the long-term strength. The failure mode of undisturbed loess changes from shear failure to homogeneous failure with increasing moisture content; when the failure mode is shear failure, the thickness of the shear band that forms at the specimen surface over time is smaller than the corresponding thickness that forms instantaneously. Finally, the macroscopic morphology and microstructure of loess specimens were considered together to analyze the effect of moisture content on the instantaneous and long-term mechanical behavior of loess and to discuss the process of loess deformation to failure.

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“…Loess is a Quaternary sedimentary soil widely distributed in Asia, Europe, America, and Africa (Wei et al, 2019a;Nan et al, 2021). In China, the loess covers an area of 631,000 km 2 .…”

Section: Introductionmentioning

confidence: 99%

“…The integration of loess dynamic properties with loess microstructure has become a critical issue, with promising findings (Nan et al, 2021;Wang et al, 2021). To simulate the earthquake process, undisturbed loess is preloaded.…”

Section: Introductionmentioning

confidence: 99%

Three-dimensional characterization and quantitative research of Malan loess microstructure under seismic loading

Wei

Chen

et al. 2023

Front. Earth Sci.

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The deformation and failure of loess in areas of high seismic intensity are closely related to the dynamic vulnerability, which is primarily controlled by the loess microstructure. This study performed a series of dynamic triaxial tests and microstructure tests on intact loess to track and quantitatively characterize the evolution of the three-dimensional microstructure during deformation. The microstructural observations were performed using micro-CT on the samples after varying vibration times. The microstructure parameters (including pore radius, elongation, orientation, coordination number, pore throat area, and channel length) were obtained using a reconstructed pore network model. The results of this study demonstrated that the loess seismic subsidence originated from both compositional and microstructural characteristics. The intact loess had a loose structure with high porosity and limited cementation. Upon cyclic loading, cementation and contact breakdown led to the failure of the loess structure, followed by particle rearrangement. With increasing vibration times, the spaced and inter-aggregate pores became intra-aggregate pores, the pore throat size tended to decrease while the pore number tended to increase, the connectivity tended to weaken, and the shape tended to be long and flat. Pores >28 μm mainly provided spatial conditions for collapse deformation under seismic load. In addition, under the ultimate loading, large-volume cracks occurred inside the sample. The findings of this study provide further insights into loess seismic subsidence from the perspective of three-dimensional microstructures and a research basis for analyzing the stability of loess in relation to construction projects by combining finite and discrete elements.

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Shear behavior and microstructural variation in loess from the Yan'an area, China

Cited by 33 publications

References 40 publications

Effect of moisture content on the time-dependent mechanical characteristics of loess

Effect of moisture content on the time-dependent mechanical characteristics of loess

Effect of Moisture Content On The Time-Dependent Mechanical Characteristics of Loess

Three-dimensional characterization and quantitative research of Malan loess microstructure under seismic loading

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