Experimental Study on the Influence of Soil Structure Index on Loess Permeability

The micro pores in loess show regional variation in structure on the Loess Plateau and greatly influence the physical properties and macro behaviors of loess. In this study, the 3D microstructures of Malan loess from Lanzhou (LZ), Qingyang (QY), Hengshan (HS) and Jingyang (JY) were established based on μ-CT scanning, and the corresponding microstructural parameters were compared and analyzed quantitatively. The results indicate that the LZ and HS loess both show overall homogeneous structures with dominant inter-particle pores, while the QY and JY loess have more intra-aggregate and constricted pores. Overall, the LZ loess has the largest pore size, followed by the JY loess, QY loess and HS loess, which is consistent with the throat sizes of the four loess samples. The average coordination numbers (CNs) of the LZ and HS loess are lower than those of the QY and JY loess, while the throat lengths of the former two loess are larger than those of the latter two loess. Analysis of the correlation between the micropore parameters and macro behaviors of the loess suggests that the void ratio is the precondition for loess collapse, but it shows weak relevance to collapsibility; meanwhile, the size of pores contributing to the major pore space presents a strong positive correlation. The throat length representing the pore structure is more closely related to loess permeability compared with the void ratio, average CN and throat size.

Section: Permeability and Pore Structurementioning

confidence: 99%

Quantitative 3D Characterization of Pore Structure in Malan Loess from Different Regions of the Loess Plateau

Nan,

Wei,

Liu

et al. 2023

“…The permeability of loess is closely linked to the pore channels between its soil particles. Due to its high water sensitivity, loess undergoes structural changes upon contact with water, leading to alterations in its permeability [68]. Compaction and water content are crucial factors that affect the microstructure of compacted loess [69].…”

Section: Pore Distribution Characteristics Under Sample Preparation M...mentioning

confidence: 99%

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

Ma,

Qiu,

Gao

et al. 2023

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.

Responses of Soil Moisture to Gully Land Consolidation in Asian Areas with Monsoon Climate

Lin,

Zhang,

Cao

et al. 2024

Groundwater resources are essential for sustaining ecosystems and human activities, especially under the pressures of climate change. This study employed Electrical Resistivity Tomography (ERT) to assess the impact of Gully Land Consolidation (GLC) engineering on the groundwater hydrological field of small watersheds in the China Loess Plateau (CLP). Results revealed ample subsurface water storage in backfilled areas, primarily migrating along the original river path owing to topographical limitations. Although the distribution patterns of soil moisture in each backfilling block varied slightly, the boundaries of soil moisture content and variation mainly appeared at depths of 8 m and 20 m underground. Significant moisture variation occurred across the 0–20 m underground layers, suggesting the 8–20 m layer could function as a groundwater collection zone in the study area. Human activities could disturb groundwater, altering migration pathways from the original river path. An optimized “Drainage–Conveyance–Barrier” system is proposed to enhance GLC sustainability, involving upstream groundwater level control, midstream soil moisture management, and downstream hydrological connectivity improvement. These findings carry substantial implications for guiding the planning and execution of GLC engineering initiatives. The novelty of this study lies in its application of ERT to provide a detailed spatial and temporal understanding of soil moisture dynamics in the GLC areas. Future research should focus on factors such as soil types and topographical changes for a comprehensive assessment of GLC’s impact on small watershed groundwater hydrology.