https://orcid.org/0000-0001-8317-7423
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ABSTRACT
To study the influence of climate and the environment on the stability of loess slopes in Yan’an, China, the macromechanical deterioration and changes in its internal structure were explored by simulating its behavior during drying, wetting, freezing and thawing under natural conditions. A triaxial apparatus was used to conduct multiple shear tests to obtain stress‒strain relationships and shear strength parameters of the soil under different cycle modes, and the results were applied to analyze the macromechanical changes of the loess samples with increasing numbers of cycles. The results of the stress‒strain curves and the trends of the shear strength parameters showed that when a sample experienced coupled dry‒wet and freeze‒thaw cycles, its shear strength was considerably lower than that under a single type of cycle. Additionally, dry‒wet cycles had a stronger negative effect than freeze‒thaw cycles on soil strength. Microscopic tests showed that the contact mode of particles tended to be unstable due to the effects of dry‒wet and freeze‒thaw cycles, resulting in the reduction of soil cementation. The results of this multiscale research provide a reference for future work on geological disaster prevention and engineering control in areas where loess is present.
Nomenclature
| B | = | Short axis length of soil particles (μm) |
| C | = | Unit abundance |
| CU | = | Solidified undrained shear test |
| Fi(α) | = | Parameter directional frequency |
| Hm | = | Probabilistic entropy of soil particle orientation |
| i | = | Soil particle orientation interval sequence number Valued from 1 to 18 |
| IPP | = | Integrated image processing software |
| L | = | long axis length of soil particles (μm) |
| M | = | Total number of soil particles |
| mi | = | Number of soil particles grouped in the nth interval in the long axis direction |
| N | = | Number of cycles corresponding to dry-wet, freeze-thaw or coupled cycles |
| n | = | Number of oriented intervals of soil particles in a two-dimensional plane from 0° to 180°, 10° equidistant intervals, 18 in total |
| NMR | = | Nuclear magnetic resonance |
| Q3 | = | Late Pleistocene (geological epoch from 2400 m years ago) |
| St | = | Target saturation of soil (%) |
| Stc | = | The target saturation value corresponding to the viscosity cohesion c as a variable |
| Stφ | = | The target saturation value corresponding to the variable internal friction angle φ |
| T2 | = | Relaxation time (ms) |
| α | = | Angle of orientation of soil particles in a two-dimensional plane from 0° to 180° (°) |
Acknowledgments
This work was supported by the National Natural Science Foundation of China (Grant no. 42072319).
Disclosure statement
No potential conflict of interest was reported by the author(s).
Data availability statement
All data, models, or code that support the findings of this study are available from the corresponding author upon reasonable request.