Heterogeneous evolution of pore structure during loess collapse: Insights from X-ray micro-computed tomography

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

doi:10.1016/j.catena.2021.105206

Cited by 29 publications

(9 citation statements)

References 35 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Hence, it is postulated that an increase of volume would occur, if a higher σ ’ 3 is applied to the dense sample. In addition, an alternative explanation at the micro scale is perhaps due to an internal collapse of pores in the loose samples, and it contributes to the marked volume change 29 .…”

Section: Test Results and Discussionmentioning

confidence: 99%

On characteristics of K0 value and shear behaviour of loess using triaxial test

Liu,

Xu,

Huang

et al. 2024

Sci Rep

View full text Add to dashboard Cite

Compared with conventional soils, such as sand and clay, little knowledge on the coefficient of lateral earth pressure at-rest (K0) has been established for loess in the current literature. This paper presents an experimental investigation on K0 of compacted loess and the associated impacts on undrained shear behaviour. By adopting a K0 consolidation module in the triaxial system, the K0 stress state for loess samples was achieved through a unique feedback control. During the K0 consolidation, the deviatoric stress (q) increases progressively with the premise that the volumetric strain (εv) of the sample equals to the axial strain (εa). The results show that the K0 value of compacted loess is in a range of 0.28 to 0.53, which is dependent on the packing density and the clay content. A distinguishable decrease of K0 was found in the course of K0 consolidation for the loosely compacted loess sample, whereas a similar trend was not observed in the dense sample. In the undrained shear stage, all loess specimens revealed contractive response in the stress path (q-p’) diagram, which can be quantified by a modified collapsibility index (Ic). The index is consistently higher for the K0 consolidated loess samples than for the isotropic ones. The experimental results indicate a strong impact of the initial stress state on the shear behaviour of compacted loess.

show abstract

Section: Test Results and Discussionmentioning

confidence: 99%

On characteristics of K0 value and shear behaviour of loess using triaxial test

Liu,

Xu,

Huang

et al. 2024

Sci Rep

View full text Add to dashboard Cite

show abstract

“…Additionally, the pores and structure of clay minerals are damaged by water swelling, collapsibility, and the water lock effect caused by water sensitivity. Specifically, the hydration and expansion of clay minerals may produce particle migration, which lead to the decline of reservoir porosity and permeability, and irreversible damage to the pore system of reservoir. − Collapsibility may lead to pore throat blockage, and poor porosity and permeability. − Also, the water lock effect caused by the increase of reservoir water saturation reduces the reservoir permeability. ,− In addition, it is not conducive to the formation and distribution of three-dimensional fracture networks in the reservoir fracturing process. − The interaction mechanism between water and clay minerals is extremely complex. So far, the damage mechanism of clay pore structure and the control mechanism of competitive adsorption of water and CH 4 have not been determined.…”

Section: Influence Of Clay Content On Ch4 Adsorption Capacity In a Sh...mentioning

confidence: 99%

Review of the Effect of Diagenetic Evolution of Shale Reservoir on the Pore Structure and Adsorption Capacity of Clay Minerals

et al. 2022

View full text Add to dashboard Cite

This Review summarizes the diagenetic evolution of clay mineral structure and pores in shale gas reservoirs. In the early diagenetic stage and in period A of the middle diagenetic stage, the intergranular and intragranular pores of clay minerals were altered by mechanical and chemical compaction, and V L (Langmuir volume) shows a positive linear correlation with clay content. In period B of the middle diagenetic stage and late diagenetic stage, intergranular pores almost disappeared, clay adsorption capacity significantly decreased, and there was a lack of apparent correlation between V L and clay content. Experimental and molecular simulations of clay adsorption capacity in shale are limited due to several drawbacks. (i) Shale samples in different diagenetic stages were characterized by strong heterogeneity, which affected the reliability of the evolution results of clay adsorption capacity. (ii) The method of selecting clay-rich shale samples, extracting clay minerals from shale, or applying pure clay minerals ignored the difference of diagenetic background, the damage of pores and structure of clay minerals, or the support of brittle minerals to shale pore system. (iii) Molecular simulation mostly employed a simplified plate model or single clay mineral model, which oversimplified the structure and diversity of clay minerals in real shale gas reservoirs. Therefore, innovative experimental simulations on the effect of diagenetic evolution on pore structure and adsorption capacity of clay minerals are necessary, which need to comprehensively weigh the combined effect of time and space on the reservoir diagenetic evolution. Besides, the visualization of shale structure, adsorption process, and CH 4 adsorption behavior of the shale constituents may help our understanding. Furthermore, a more accurate model of the molecular structure of clay minerals is indispensable, especially the dynamic evolution model with different water contents.

show abstract

“…Micro-CT scans have been performed on saline intact loess to investigate the relationship between loess microstructure and hydraulic conductivity under freeze-thaw cycle conditions (Xu et al, 2020b). Based on the evaluation of the 3D pore structure of loess by X-ray scanning (Chen et al, 2019;Li and Shao, 2020), two different types of pores have been extracted, providing new research ideas on loess collapse (Yu et al, 2021). With the development of micron scanning equipment, research on loess microstructure is maturing.…”

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.

View full text Add to dashboard Cite

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.

show abstract

Heterogeneous evolution of pore structure during loess collapse: Insights from X-ray micro-computed tomography

Cited by 29 publications

References 35 publications

On characteristics of K0 value and shear behaviour of loess using triaxial test

On characteristics of K0 value and shear behaviour of loess using triaxial test

Review of the Effect of Diagenetic Evolution of Shale Reservoir on the Pore Structure and Adsorption Capacity of Clay Minerals

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

Contact Info

Product

Resources

About