Permeability characteristics and structural evolution of compacted loess under different dry densities and wetting-drying cycles

Autor: Xi-jun Wang, Xiang-fei Lü, Kang-ze Yuan, Wan-kui Ni
Rok vydání: 2021
Předmět:
Distribution Curves
Pedology
Loess
Mosaic Structures
Spectrum analysis techniques
Soil
Materials Physics
Relaxation Time
Composite material
Microstructure
Soil mechanics
Sedimentary Geology
Multidisciplinary
Crystallography
Physics
Software Engineering
Geology
Condensed Matter Physics
Permeability (earth sciences)
Physical Sciences
Crystal Structure
Medicine
Engineering and Technology
Wetting
Saturation (chemistry)
Research Article
Statistical Distributions
Computer and Information Sciences
Materials science
Science
Materials Science
Material Properties
Soil Science
Permeability
Computer Software
NMR spectroscopy
Solid State Physics
Desiccation
Relaxation (Physics)
Petrology
Aggregate (composite)
Macropore
Water
Probability Theory
Research and analysis methods
Volume (thermodynamics)
Models
Chemical
NMR relaxation
Wettability
Earth Sciences
Sediment
Mathematics
Zdroj: PLoS ONE
PLoS ONE, Vol 16, Iss 6, p e0253508 (2021)
ISSN: 1932-6203
Popis: Permeability characteristics of compacted loess is always an important topic in soil mechanics and geotechnical engineering. This study explored the permeability characteristics of compacted loess under different dry densities and wetting-drying cycles, and found that as the dry density increases, the compacted loess surface became denser, the saturation permeability coefficient and saturation infiltration rate decreased. However, the wetting-drying cycle presented the opposite result. Meanwhile, the evolution of the microstructure was investigated by Scanning Electron Microscope (SEM) and Nuclear Magnetic Resonance (NMR) to explain the change of its permeability characteristics. The size of compacted loess aggregates was quantitatively analyzed by Image-Pro Plus (IPP) software. It showed that the size of compacted loess aggregates for different dry densities were concentrated from 10–100 μm, occupying 65.0%, 58.19%, and 51.64% of the total aggregates area respectively. And the interesting finding was that the area occupied by 10–50 μm aggregates remained basically unchanged with the number of wetting-drying cycles increasing. Therefore, the size of 10–50 μm aggregates represented the transition zone of compacted loess. NMR analyses revealed that with increasing dry density, the volume of macropores in the compacted loess rapidly decreased, the volume of mesopores and small pores increased. Meanwhile, the change in micropores was relatively small. The pore volume of the compacted loess after three wetting-drying cycles increased by 8.56%, 8.61%, and 6.15%, respectively. The proportion of macropores in the total pore volume shows the most drastic change. Variations in aggregate size and connection relationships made it easier to form overhead structures between aggregates, and the increased of macropore volume will form more water channels. Therefore, the change in permeability characteristics of compacted loess is determined by aggregate size, loess surface morphology, and the total pore volume occupied by macropores.
Databáze: OpenAIRE
Externí odkaz:
Nepřihlášeným uživatelům se plný text nezobrazuje