Effect of Water Content on Strength of Alluvial Silt in The Lower Yellow River
Abstract
:1. Introduction
2. Test Equipment and Method
2.1. SWCC Test
2.2. Direct Shear Test of Unsaturated Soil
3. Test Result and Analysis
3.1. SWCC Test
3.1.1. SWCC Test Results
3.1.2. SWCC Model Fitting
3.2. Direct Shear Test
3.2.1. Direct Shear Test Results
3.2.2. Effect of Moisture Content on Shear Strength Parameters
3.3. Prediction of Shear Strength Parameters of Unsaturated Silt in the Lower Yellow River
3.3.1. Study on the Effective Stress Parameters χ
3.3.2. Prediction of Effective Stress Parameters χ of Unsaturated Silt in The Lower Yellow River
3.3.3. Prediction of Shear Strength of Unsaturated Silt in The Lower Yellow River
4. Conclusions
- The drying curve of silt samples from the lower Yellow River can be fitted by using the VG model, and the fitting parameters are as follows: a = 13.699 (kPa−1), m = 0.554, n = 2.241, and Sr = 9.965 (%);
- As moisture content changes from a lower state to a higher state, the shear displacement and shear stress curves show shear softening and shear hardening behavior, respectively;
- Moisture content has a nonlinear inverse relationship with cohesion. The increase in moisture content results in a variation of friction angle and no clear law for this variation is defined. Furthermore, compared with the internal friction angle, moisture content has a greater influence on cohesion;
- The relationship between effective stress parameters and the degree of saturation of the silt in the lower Yellow River is proposed and validated by tests on the specific sample material in this study, which can be expressed as follows:
- 5.
- Based on the Bishop’s shear strength equation, this study suggests an empirical equation of shear strength for silt in the lower Yellow River channel, which includes the function of cohesion, friction angle and suction. The shear strength can be evaluated at the corresponding suction with a certain cohesion and friction angle, by using the equation below.
Author Contributions
Funding
Data Availability Statement
Acknowledgments
Conflicts of Interest
References
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Yellow River Silt | Natural Moisture Content ω/% | Natural Gravity Gs/kN/m3 | Void Ratio e | Natural Saturation S′/% |
15.38 | 25.10 | 0.663 | 58.23 |
Fitting Parameters | a/kPa−1 | m | n | Sr/% |
---|---|---|---|---|
VG model fitting values | 0.0730 | 0.554 | 2.241 | 9.965 |
Moisture Content ω (%) | Degree of Saturation S (%) | Normal Stress σ (kPa) | τmax (kPa) | ctotal (kPa) | φtotal (°) |
---|---|---|---|---|---|
5.30% | 20% | 25 | 48 | 30.5 | 37.52 |
50 | 73 | ||||
75 | 85 | ||||
100 | 108 | ||||
10.60% | 40% | 25 | 42 | 21.5 | 38.24 |
50 | 58 | ||||
75 | 84 | ||||
100 | 99 | ||||
15.85% | 60% | 25 | 37 | 17 | 37.67 |
50 | 53 | ||||
75 | 78 | ||||
100 | 93 | ||||
21.10% | 80% | 25 | 33 | 15.5 | 38.10 |
50 | 57 | ||||
75 | 76 | ||||
100 | 92 | ||||
37.86% | 100% | 25 | 24 | 7 | 39.21 |
50 | 52 | ||||
75 | 70 | ||||
100 | 86 |
Name | Unsaturated Soil Strength Equation is Commonly Used Currently | Meaning of Physical Quantity |
---|---|---|
The Effective Stress Parameters in the Shear Strength Equation Are Summarized | ||
Bishop’s shear strength equation [7] | τf is shear stress at failure; c′ is effective cohesion of saturated soil; σ is net normal stress; ua is the pore water pressure; uw is the pore gas pressure; χ is effective stress parameters; φ′ is effective angle of internal friction of saturated soil. | |
Khalili’s equation for predicting additional suction strength from soil–water characteristics curves [29] | θ(ψ) is volumetric water content under different suction forces which is represented by the soil–water characteristics curve equation; θs is saturated volumetric water content; K is a fitting parameter for effective stress. | |
Vanapalli and Fredlund’s equation for unsaturated soil strength at different moisture content [30] | θ is volumetric water content; θr is residual volumetric water content; Se is the effective degree of saturation; Sr is the residual degree of saturation. | |
Degree of Saturation S/% | Matric Suction/kPa | Normal Stress /kPa | Shear Strength/kPa | Angle of Internal Friction/° | Cohesion/kPa | Effective Stress Parameters χ | Average Value of χ |
---|---|---|---|---|---|---|---|
0 | / | / | / | / | / | / | 0.000 |
20 | 79.52 | 25 | 48 | 37.52 | 30.5 | 0.087 | 0.115 |
50 | 73 | 0.182 | |||||
75 | 85 | 0.064 | |||||
100 | 108 | 0.126 | |||||
40 | 31.04 | 25 | 42 | 38.24 | 21.5 | 0.319 | 0.286 |
50 | 58 | 0.168 | |||||
75 | 84 | 0.425 | |||||
100 | 99 | 0.233 | |||||
60 | 18.19 | 25 | 37 | 37.67 | 17 | 0.548 | 0.498 |
50 | 53 | 0.313 | |||||
75 | 78 | 0.719 | |||||
100 | 93 | 0.413 | |||||
80 | 10.69 | 25 | 33 | 38.10 | 15.5 | 0.585 | 0.836 |
50 | 57 | 1.110 | |||||
75 | 76 | 1.038 | |||||
100 | 92 | 0.609 | |||||
100 | 0 | / | / | 39.21 | 7 | / | 1.000 |
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Cheng, Y.-Y.; Gao, X.-G.; Liu, T.-H.; Li, L.-X.; Du, W.; Hamad, A.; Wang, J.-P. Effect of Water Content on Strength of Alluvial Silt in The Lower Yellow River. Water 2022, 14, 3231. https://doi.org/10.3390/w14203231
Cheng Y-Y, Gao X-G, Liu T-H, Li L-X, Du W, Hamad A, Wang J-P. Effect of Water Content on Strength of Alluvial Silt in The Lower Yellow River. Water. 2022; 14(20):3231. https://doi.org/10.3390/w14203231
Chicago/Turabian StyleCheng, Yang-Yang, Xu-Guang Gao, Tai-Heng Liu, Lian-Xiang Li, Wei Du, Abu Hamad, and Ji-Peng Wang. 2022. "Effect of Water Content on Strength of Alluvial Silt in The Lower Yellow River" Water 14, no. 20: 3231. https://doi.org/10.3390/w14203231
APA StyleCheng, Y. -Y., Gao, X. -G., Liu, T. -H., Li, L. -X., Du, W., Hamad, A., & Wang, J. -P. (2022). Effect of Water Content on Strength of Alluvial Silt in The Lower Yellow River. Water, 14(20), 3231. https://doi.org/10.3390/w14203231