Experimental Study on the Effects of Freeze–Thaw Cycles on Strength and Microstructure of Xining Region Loess in China
Abstract
:1. Introduction
2. Materials and Methods
2.1. Sample Preparation
2.2. Experimental Design
2.3. Basic Physical Properties of Loess
3. Analysis of Micro-Test Results
3.1. SEM Test
3.2. XRD and XRF Test
4. Analysis of Mechanical Test Results
4.1. Unconfined Compressive Strength
4.2. Stress–Strain Curve
4.3. Elastic Modulus
5. Conclusions
- With an increasing number of freeze–thaw cycles, the unconfined compressive strength of undisturbed loess and remolded loess first increases and then decreases as the strain increases, and the stress–strain curve exhibits strain-softening characteristics. During the freeze–thaw cycle, through the mutual conversion of free water to ice water inside the sample, the structure of the loess is destroyed. At the same time, due to the influence of the primary structure, the unconfined compressive strength of the undisturbed loess is higher than remolded loess.
- The unconfined compressive strength of undisturbed loess and remolded loess decreases after 6 freeze–thaw cycles, and the strength increases after 8 to 20 freeze–thaw cycles.
- It can be seen from the SEM images that with increasing freeze–thaw cycles, the large particles inside the sample gradually decompose into small particles, increasing the fine particles inside the sample. At the same time, the larger pores inside the sample gradually reduce in size. With the increase in the number of freeze–thaw cycles, the particles inside the soil become denser, and the strength increases.
- The mineral composition of loess after freeze–thaw cycles are studied, and it is found that the internal composition of loess did not change significantly, and the mineral content is stable. Therefore, the effect of freeze–thaw cycles on the mineral composition of loess can be ignored in engineering.
Author Contributions
Funding
Institutional Review Board Statement
Informed Consent Statement
Data Availability Statement
Conflicts of Interest
References
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Type of Soil | Freeze–Thaw Cycle Test | UCS Test | SEM Test | XRD and XRF Test |
---|---|---|---|---|
Undisturbed loess | (1) Freeze–thaw cycles were 0, 2, 4, 6, 8, 10, 15, 20 | Each group has 3 samples, a totalof 48 samples | Each group has 2 samples, a totalof 32 samples | Each group has 2 samples, a totalof 32 samples |
Remolded loess | (2) The freezing and thawing temperature was set as ±15 °C | |||
(3) 12 h for freezing and 12 h for thawing as a cycle |
Specific Gravity of Soil Solids (Gs) | Natural Water Content (%) | Dry Density (g/cm3) | Liquid Limit (%) | Plastic Limit (%) |
---|---|---|---|---|
2.71 | 13.40 | 1.72 | 25.30 | 13.95 |
Chemical Constituent (Mass%) Freeze–Thaw Cycles | SiO2 | Al2O3 | CaCO3 | MgO | K2O | Na2O | Fe2O3 | Others |
---|---|---|---|---|---|---|---|---|
0 times | 48.0 | 13.5 | 25.9 | 3.15 | 2.74 | 1.26 | 4.17 | 1.28 |
2 times | 48.8 | 14.0 | 24.4 | 3.25 | 2.84 | 1.32 | 4.28 | 1.11 |
6 times | 49.4 | 13.7 | 24.1 | 3.27 | 2.82 | 1.35 | 4.28 | 1.08 |
10 times | 49.1 | 13.5 | 24.8 | 3.13 | 2.70 | 1.30 | 4.28 | 1.19 |
20 times | 48.8 | 13.5 | 24.4 | 3.06 | 2.85 | 1.29 | 4.80 | 1.30 |
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Xie, B.; Zhang, W.; Sun, X.; Huang, Y.; Liu, L. Experimental Study on the Effects of Freeze–Thaw Cycles on Strength and Microstructure of Xining Region Loess in China. Buildings 2022, 12, 795. https://doi.org/10.3390/buildings12060795
Xie B, Zhang W, Sun X, Huang Y, Liu L. Experimental Study on the Effects of Freeze–Thaw Cycles on Strength and Microstructure of Xining Region Loess in China. Buildings. 2022; 12(6):795. https://doi.org/10.3390/buildings12060795
Chicago/Turabian StyleXie, Banglong, Wuyu Zhang, Xianglong Sun, Yuling Huang, and Leqing Liu. 2022. "Experimental Study on the Effects of Freeze–Thaw Cycles on Strength and Microstructure of Xining Region Loess in China" Buildings 12, no. 6: 795. https://doi.org/10.3390/buildings12060795