Collapsibility, composition, and microstructure of loess in China

Liu, Zhen; Liu, Fengyin; Ma, Fuli; Wang, Mei; X, Bai; Zheng, Yonglai; Yin, Huiming; Zhang, Guoping

doi:10.1139/cgj-2015-0285

Cited by 250 publications

(91 citation statements)

References 35 publications

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“…In the unamended condition, the fine sand particles are largely cohesionless and weakly structured (Abousnina et al, 2015), and can not withstand high shear stress values. The amend ments provided either clay or biochar coating on the finesand particles, which act synergistically to augment interparticle cementation depending on the chemical properties of the biochar and clay materials and the matric potential (Liu et al, 2015). Additionally, the amendment furthermore affects the cation exchange capacity (CEC) and reduces the water repellency risk (McKissock et al, 2000;Meisl et al, 2013).…”

Section: Discussionmentioning

confidence: 99%

Comparing the potentials of clay and biochar in improving water retention and mechanical resilience of sandy soil

Ajayi¹,

Horn²

2016

International Agrophysics

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A b s t r a c t. Changing climate is threatening rainfall regularity particularly in the semi-arid and arid regions; therefore, strategies to conserve water within their coarse-grained soils and to improve water use efficiency of crops are critical. This study compared the effectiveness of biochar and two types of clay materials in augmenting water retention and improving mechanical resilience of fine sand. The amendment of fine sand with woodchip-biochar and kaolinite (non-swelling clay) and Na-bentonite (swelling clay) improved the water retention capacity and interparticle bonding of the substrate depending of the rate of amendment and water content of the substrates. Na-bentonite was more effective at increasing water retention capacity at more negative matric potentials. Biochar was more effective at saturation due to the increased porosity, while kaolinite responds similarly to biochar. It is, however, shown that most of the water retained by the Na-betonite may not be available to plants, particularly at high amendment rate. Furthermore, the clay and biochar materials improved particle bonding in the fine sand with the Na-bentonite being more effective than biochar and kaolinite (in that order) in strengthening interparticle bonds and improving the resilience of fine sand, if the rate of amendment is kept at ≤50 g kg -1 .

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Section: Discussionmentioning

confidence: 99%

Comparing the potentials of clay and biochar in improving water retention and mechanical resilience of sandy soil

Ajayi¹,

Horn²

2016

International Agrophysics

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“…Moreover, collapsible loess is developed with a relatively large thickness in the tunnel area. In engineering characteristics, collapsible loess belongs to a metastable structure which can withstand high vertical loads with a small amount of settlement at dry, but this soil is particularly susceptible to certain water conditions, which shows an upsurge in settlement, a plunge in load capacity upon wetting and contributes to a safety hazard for infrastructures constructed in this region [49][50][51]. e collapsible thickness of general eolian loess Q 3 eol is 0∼20 m, with Grade II-III self-weight collapsibility.…”

Section: Engineering Overviewmentioning

confidence: 99%

Displacement and Stress Characteristics of Tunnel Foundation in Collapsible Loess Ground Reinforced by Jet Grouting Columns

Liu

et al. 2018

Advances in Civil Engineering

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Collapsible loess tunnel foundation reinforcement is a new challenge in the construction process of tunnel engineering. According to the field displacement and stress monitoring of the Fujiayao loess tunnel, this paper investigates the reinforcing effect of a high-pressure jet grouting pile on a collapsible loess tunnel foundation in the deep large-span tunnel. The field monitoring method was employed to address the performance of tunnel foundation settlement, additional stress, earth pressure, rock pressure, etc. The results indicate that the stress on the pile tops and the earth pressure between piles increase gradually over time in two stages: stress increases rapidly in the first 45 days and, after this period, stress tends to gradually stabilize. Further, stress increases uniformly with the distance from the centerline of the tunnel, and the rock pressure of the tunnel sidewalls tends to be stable within two months of being constructed. Additional stress on the tunnel foundation increases linearly with time, and it is uniformly distributed in the vertical and horizontal directions of the tunnel section. Settlement of the tunnel foundation also gradually increases with time, and it tends to be stable at 50 days from the time of construction. Additionally, the settlements of different monitoring points are similar at the same depth. The research results will further improve the theoretical knowledge of tunnel bottom reinforcement in the loess tunnel, which not only can effectively guide the design and construction of the loess tunnel and reduce disease treatment cost but also can provide the necessary basic research data and scientific theoretical basis for revision of the corresponding specifications of highway tunnels and railway tunnels.

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“…At the same time, the strength will suddenly decrease drastically and the deformation will be greatly accelerated, which may lead to various geological disasters. (Liu et al, 2015;Xie et al, 2018;Lal, 2019).…”

Section: Introductionmentioning

confidence: 99%

DEM analyses of true triaxial and wetting tests on unsaturated structural loess

Jiang

Wang

Lei

et al. 2020

JGS Special Publication

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Three-dimensional DEM (discrete element method) simulations of the true triaxial and wetting tests were conducted to study the macroscopic and microscopic mechanical properties of unsaturated structural loess under complex stress state. The simulation results were analyzed in terms of stress-strain relationships, void ratio responses and bond breakage number with water content. It is shown that collapsing failure occurs when the deviatoric stress approaches or exceeds the peak shear strength of the corresponding saturated structural loess sample. There is little difference in the axial strain between the quick wetting (QW) method and gradual wetting (GW) method, and the volumetric strain of the samples wetted by QW are larger than that by GW specimen. The bond breakage number of the sample wetted by QW is slightly higher than that by GW. However, the bond breakage number of the sample wetted by the two wetting methods is slightly higher than that of the saturated structural loess sample subjected to the same stress state.

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Collapsibility, composition, and microstructure of loess in China

Cited by 250 publications

References 35 publications

Comparing the potentials of clay and biochar in improving water retention and mechanical resilience of sandy soil

Comparing the potentials of clay and biochar in improving water retention and mechanical resilience of sandy soil

Displacement and Stress Characteristics of Tunnel Foundation in Collapsible Loess Ground Reinforced by Jet Grouting Columns

DEM analyses of true triaxial and wetting tests on unsaturated structural loess

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