Abstract
To study the strength degradation mechanism of compacted loess during dry‐wet cycles, 0–5 dry‐wet cycles tests and many triaxial compression tests were carried out on loess with an optimal moisture content. During the dry‐wet cycles, the loess samples were analyzed by nuclear magnetic resonance and scanning electron microscopy. Studies have shown that at the macro level, with increasing numbers of wet and dry cycles and increasing cycle amplitude, the cohesive force and internal friction angle of the loess decrease, and the shear strength of the loess deteriorates significantly. At the micro level, with the number of wet and dry cycles increasing, the connection between particles changes from surface‐to‐surface contacts to point‐to‐point or point‐to‐surface contacts. The edges and corners of the particles decrease, the roundness increases, the large pores gradually decrease, the small pores gradually increase, and the fractal dimension gradually increases. In terms of microscopic view, the NMR test shows that with increasing numbers of dry‐wet cycles, the T2 peak curve increases, the curve width increases slightly, the peak area gradually increases, and the porosity increases. From the macroscopic, mesoscopic, and microscopic multiscale analysis, the structure of loess is degraded under the action of dry and wet cycles; the strength of the loess is degraded significantly after 0 to 3 cycles and then gradually stabilizes. These research results can provide a certain reference value for the management of loess collapse geological disasters in semiarid climates.
Highlights
In Northwest China, loess is distributed everywhere
Razouki et al [4] conducted a systematic experimental study on the strength and deformation of gypsum-rich sand used in subgrade construction under the action of dry-wet cycles and obtained certain results
Wu et al [6] studied the mechanical properties of improved expansive soil under the action of dry-wet cycles and provided a reference for the construction of Advances in Materials Science and Engineering roadbeds and other projects. de Oliveira et al [7] used X-ray computed tomography to study the porosity changes in cultivated soil under the action of dry-wet cycles; Liu et al [8] used triaxial strength tests, nuclear magnetic resonance, and scanning electron microscopy on expansive soil under the action of dry-wet cycles to study the macromechanical behavior and the microstructure damage to the regularity of soil
Summary
In Northwest China, loess is distributed everywhere. due to the complex terrain, vertical and horizontal ravines, harsh environment, and unique climate in the loess area, and under natural and anthropogenic actions, loess is extremely prone to disasters such as landslides, collapses, and soil erosion, which seriously endanger engineering construction and the safety of people’s lives and property and restrict the sustainable development of the local economy [1, 2]. is article focuses on water, a key factor that causes loess collapse, and studies loess bodies through the evaporation of water, that is, dry-wet cycles; the results reveal the mechanism of loess structural degradation from a multiscale perspective. e study has important academic value, scientific significance, and essential practical value and significance for the construction of basic projects in the future. e research results will provide a more scientific theoretical basis for the engineering practice of disaster prevention and mitigation in the process of project site selection, construction, and operation in the loess area. E research results will provide a more scientific theoretical basis for the engineering practice of disaster prevention and mitigation in the process of project site selection, construction, and operation in the loess area. Wu et al [6] studied the mechanical properties of improved expansive soil under the action of dry-wet cycles and provided a reference for the construction of Advances in Materials Science and Engineering roadbeds and other projects. Based on the macroscopic triaxial test, the author used electron scanning microscopy (SEM) and nuclear magnetic resonance (NMR) technology to analyze the pore structure of loess under different cycles and conducted a multiscale analysis of the changes in the mechanical properties of loess under the action of dry-wet cycles from different perspectives. Based on the macroscopic triaxial test, the author used electron scanning microscopy (SEM) and nuclear magnetic resonance (NMR) technology to analyze the pore structure of loess under different cycles and conducted a multiscale analysis of the changes in the mechanical properties of loess under the action of dry-wet cycles from different perspectives. is study aims to provide a reference for the management of loess collapse geological disasters in semiarid areas
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