Structural Characteristics of Natural Loess in Northwest China and its Effect on Shear Behavior

Wang, Yong; Hui, Yang; Xu, Jing

doi:10.1007/s10706-020-01420-4

Cited by 9 publications

(7 citation statements)

References 36 publications

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“…The mechanical properties of soil are closely related to its microstructure. The relationship between the shear characteristics of soil and its microstructural changes was discussed by some scholars [ 26 , 27 ]. Moreover, the dynamic characteristics of loess and the variation of the characteristics in the micro-mechanisms therein have also been explored [ 28 , 29 ].…”

Section: Introductionmentioning

confidence: 99%

Microstructural Variation of Clay during Land Subsidence and the Correlation between Macroscopic and Microscopic Parameters

Jia

Ding

et al. 2022

Materials

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The nonlinear deformation, visco-elasto-plasticity and other macroscopic properties of soil are the concentrated manifestations of its microstructural state. In order to study the microstructural characteristics and variations of the clay under the action of additional stress caused by groundwater exploitation, borehole sampling was carried out on the clay layers at different depths in a typical land subsidence area. Consolidation tests, freeze-drying, ion sputtering, and scanning electron microscope (SEM) were conducted in order to scan and analyze the microstructure of the test samples at different scales. The Particles and Cracks Analysis System (PCAS) was used to quantify the microscopic parameters, the variations of the microstructural parameters with consolidation loads at different sizes were revealed, and the correlation between the macroscopic and microscopic parameters were discussed. The results show that: (1) the microstructural characteristics of soils with different buried depths have directivity, to a certain extent; (2) as the consolidation load increases, the average unit area and average form factor of the soil microstructure generally decrease, the structural arrangement of the unit gradually tends to be orderly, and the average pore area, apparent void ratio and the number of pores generally show a decreasing trend; (3) under the action of a consolidation load, when the microstructure at a relatively large scale is basically stable, the microstructure at a smaller scale will continue to adjust; (4) the apparent void ratio has a good linear regression relationship with the conventional void ratio, and the apparent void ratio has a good exponential growth relationship with the compressibility.

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Section: Introductionmentioning

confidence: 99%

Microstructural Variation of Clay during Land Subsidence and the Correlation between Macroscopic and Microscopic Parameters

Jia

Ding

et al. 2022

Materials

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“…It can be seen from Fig 12 that under the same vertical pressure, the shear stress-shear displacement curves of low water content 4 # and 22 # specimens are hardening type. When the specimen with higher water content reaches the peak strength, the corresponding shear deformation is small, and the strength softening is also easy to occur (the softening phenomenon of 23 # specimen with the water content of 19% is obvious), that is, the process of attenuation from the peak strength includes two stages: the first stage is that the shear dilatancy increases the pore water content and then leads to strain softening, and the second stage is that with the increase of shear strain, the loess particles gradually reach the residual strength along the shear direction [ 5 ]. When the shear displacement reaches about 60 mm, the shear stress of each water content specimen has basically reached a stable value, and the specimens have reached the residual strength.…”

Section: Methodsmentioning

confidence: 99%

“…Mitchell [ 1 ] believed that the structure of soil was based on the arrangement and cementation between particles. Wu [ 2 ], Tan [ 3 ] studied the macroscopic mechanical characteristics of loess through triaxial test and Li [ 4 ], Wang [ 5 ] explained the microstructure characteristics of loess specimens before and after triaxial test. Jing [ 6 ], Xie [ 7 ] studied the interfacial shear behavior between loess and structure from the macro and micro perspectives.…”

Section: Introductionmentioning

confidence: 99%

“…R-V. Matalucci [ 16 – 18 ] combined with triaxial tests with the structure model using Vixburg loess as granular soil material to explain that the structure has a significant impact on the ultimate strength. Li [ 19 ], Deng [ 20 ], Wang [ 5 ], Wei [ 21 ], Samoilych [ 22 ], Ng C.W.W. [ 23 ], Sadeghi [ 24 ], Ding [ 25 ], Nan [ 26 ], et al analyzed the influence of microstructure and structural changes on the strength and deformation characteristics of soil.…”

Section: Introductionmentioning

confidence: 99%

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Influence mechanism of structure on shear mechanical deformation characteristics of loess-steel interface

et al. 2022

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The mechanical properties of loess-steel interface are of great significance for understanding the residual strength and deformation of loess. However, the undisturbed loess has significant structural properties, while the remolded loess has weak structural properties. There are few reports on the mechanical properties of loess-steel interface from the structural point of view. This paper focused on the ring shear test between undisturbed loess as well as its remolded loess and steel interface under the same physical mechanics and test conditions (water content, shear rate and vertical pressure), and explored the influence mechanism of structure on the mechanical deformation characteristics of steel-loess interface. The results show that the shear rate has little effect on the residual strength of the undisturbed and remolded loess-steel interface. However, the water content has a significant influence on the residual strength of the loess-steel interface, moreover, the residual internal friction angle is the dominant factor supporting the residual strength of the loess-steel interface. In general, the residual strength of the undisturbed loess-steel interface is greater than that of the remolded loess specimen (for example, the maximum percentage of residual strength difference between undisturbed and remolded loess specimens under the same moisture content is 6.8%), which is because that compared with the mosaic arrangement structure of the remolded loess, the overhead arrangement structure of the undisturbed loess skeleton particles makes the loess particles on the loess-steel interface re-adjust the arrangement direction earlier and reach a stable speed relatively faster. The loess particles with angular angles in the undisturbed loess make the residual internal friction between the particles greater than the smoother particles of the remolded loess (for example, the maximum percentage of residual cohesion difference between undisturbed and remolded loess specimens under the same vertical pressure is 4.29%), and the intact cement between undisturbed loess particles brings stronger cohesion than the remolded loess particles with destroyed cement (for example, the maximum difference percentage of residual cohesion between undisturbed and remolded soil specimens under the same vertical pressure is 33.80%). The test results provide experimental basis for further revealing the influence mechanism of structure, and parameter basis for similar engineering construction.

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“…Quantitative data on loess particles and pore structure have been analyzed through SEM images to summarize the changes in pore quantity, area, and form corresponding to different dynamic loading stages Lian et al, 2022). The MIP technique is widely used in the study of loess pore size and collapsibility (Mu et al, 2020;Wang et al, 2021). Based on MIP tests, scholars have explored the impacts of different cycles on soil mechanics and pore characteristics, indicating that the cycling effects play a dominant role in the deterioration of loess engineering properties (Li et al, 2019;.…”

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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Structural Characteristics of Natural Loess in Northwest China and its Effect on Shear Behavior

Cited by 9 publications

References 36 publications

Microstructural Variation of Clay during Land Subsidence and the Correlation between Macroscopic and Microscopic Parameters

Microstructural Variation of Clay during Land Subsidence and the Correlation between Macroscopic and Microscopic Parameters

Influence mechanism of structure on shear mechanical deformation characteristics of loess-steel interface

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

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