Experimental Study on the Effects of New Foam on the Improvement of Sandy Soil for Earth Pressure Balance Shield
Abstract
:1. Introduction
2. Experimental Study on Foam Agent for Shield
2.1. Choice of Foaming Agent
2.2. Performance Evaluation of a Single Surfactant
- Two surfactants, hexadecyl trimethyl ammonium chloride and hexadecyl trimethyl ammonium bromide, have the best foaming properties. Both are cationic surfactants, but they are expensive and do not conform to the principle of economy.
- Compared with several anionic surfactants, AS can achieve good foaming properties at very small concentrations. However, because of its short half-life, it cannot be used as a foaming agent alone;
- SDS and ABS have relatively good bubbles and half-lives. OP-10, dodecyl dimethyl betaine (BS-12), itself is a liquid; it is very conducive to the preparation of a water-based foam agent.
- Therefore, the selected experimental drugs are SDS, OP-10, ABS, AS and (BS-12).
- (1)
- Record the time corresponding to the solution level falling to 150 mL, then stop the solution flow, and measure the foam volume for 30 s, 3 min and 5 min.
- (2)
- If the upper center of the foam is low-lying, record the reading by the arithmetic mean between the center and the edge.
- (3)
- Repeat the test to achieve a minimum of 3 errors in the allowable range.
- (4)
- The results are expressed as the number of milliliters of foam formed after the flow stops at 30 s, 3 min, and 5 min, and the corresponding curve can be drawn if necessary. Using the arithmetic mean of the repeated measurement results as the final result, the difference between the repeated measurement results should not exceed 15 mL.
2.2.1. Program I: A/B Multiplexing System
2.2.2. Program II: A/C Multiplexing System
2.2.3. Program III: A/D Multiplexing System
2.2.4. Program IV: A/E Multiplexing System
2.3. Bubble Stabilizer
2.3.1. Effect of Polyacrylamide (W) on the Foaming System
2.3.2. Effect of Sodium Carboxymethyl Cellulose (X) on the Foaming System
2.3.3. Effect of Dodecanol (Y) on the Foaming System
2.4. Adhesives
2.5. Configuration of Foam Agent Finished Products
2.6. Foam Agent Performance Evaluation Study
2.6.1. Experimental Analysis of Foaming Rate and Stability
2.6.2. Foam Microscopic Morphological Observation and Analysis
2.6.3. Foam Resistance Study
3. Test on Improvement Effect of New Foam Sand
- i
- The particle grade of the formulated soil must conform to the particle grade of the actual soil.
- ii
- The prepared soil should be representative and typical.
- iii
- The preparation of 3 soil bodies should be repeatable, making the test process of soil body improvement repetitive.
3.1. Analysis of Results of Agitation Test
3.2. Analysis of Friction Coefficient Test Results
3.3. Analysis of Adhesion Resistance Test Results
3.4. Analysis of Collapse Test Results
3.5. Analysis of the Straight Shear Test
3.6. Comprehensive Analysis of Soil Improvement Tests
4. Conclusions
- The new foam agent formulation is obtained by experimenting and combining with the actual product configuration method: 1.6% sodium dodecyl sulfate (SDS) + 8% dodecyl dimethyl betaine (BS-12) + 7% dodecanol + 0.06% guar gum + 0.6% ammonium chloride.
- The foaming rate, stability, microstructure and temperature resistance of the new foam are evaluated. Compared with the domestic foam and imported foam commonly used in shield construction at present, the performance of the new foam meets the requirements of shield construction.
- The effect of foam on soil improvement is also related to the amount of foam added. Because of the structural characteristics of the foam itself, too little foam is added to the opposite effect and too much is added to the foam to produce waste. The cost is too high for actual construction, which should be avoided resolutely in shield construction.
- In the test of foam-improved sand soil, all three foam agents have an obvious improvement effect on sand soil. By comparing the test data, it can be found that the new foam is dominant in the friction coefficient test and adhesion resistance test. Imported foam is dominant in the mixing test and collapse test, and the improvement effect of domestic foam in the straight shear test is dominant. According to the comprehensive analysis, the combined effects of three kinds of foam-improved sand and soil are basically the same, which can meet the requirements of shield construction.
- The foam soil improvement effect test was carried out, and the allocated soil was anhydrous soil. Although it had a certain reference value for soil improvement, the water content of each stratum was different in specific engineering practice. In the next test, it is necessary to improve the soil mass with different water contents, evaluate the impact of water content on the improvement effect of foam soil mass, and more closely link the new foam with the project.
- The soil parameters selected in this project are few, and the measurement of improved soil parameters needs to be expanded in the next step. For example, the permeability coefficient, compression coefficient, etc., for further design of an indoor simulation test is required.
- In the soil improvement test of this subject, the concentration of the foam agent only uses a preset value. In the next step, the improvement effect of different foam agent concentrations on soil can be studied through a simulation test.
Author Contributions
Funding
Data Availability Statement
Conflicts of Interest
References
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Type | Name of Surfactant | Specifications | Place of Origin |
---|---|---|---|
Anionic surfactant | Sodium dodecyl sulfate (SDS) | Chemically pure | Sinopharm Chemical Reagents Co., Ltd. (Shanghai, China) |
Sodium dodecyl sulfonate (AS) | Chemically pure | Sinopharm Chemical Reagents Co., Ltd. | |
Sodium dodecyl benzene sulfonate (ABS) | Chemically pure | Sinopharm Chemical Reagents Co., Ltd. | |
Non-ionic surfactant | OP-10 (Qulatong X-100) | Chemically pure | Beijing Chemical Reagent Company (Beijing, China) |
Cationic surfactant | Cetyltrimethylammonium chloride | Chemically pure | Tianjin Nankai Yungong Synthetic Technology Co., Ltd. (Beijing, China) |
Cetyltrimethylammonium bromide | Chemically pure | Sinopharm Chemical Reagents Co., Ltd. | |
Zwitterionic surfactant | Dodecyl dimethyl betaine (BS-12) | Industrial | Tianjin Xianguang Chemical Co., Ltd. (Tianjin, China) |
Concentration of W (Mass Fraction) | 0 | 0.05% | 0.1% | 0.15% | 0.2% | 0.25% | 0.3% | 0.35% | 0.4% | 0.45% | 0.5% |
---|---|---|---|---|---|---|---|---|---|---|---|
Foam volume/mL | 940 | 930 | 910 | 910 | 900 | 870 | 840 | 840 | 760 | 750 | 750 |
Half-life/s | 450 | 560 | 640 | 700 | 720 | 820 | 840 | 930 | 1080 | 1210 | 1020 |
Concentration of X (Mass Fraction) | 0 | 0.05% | 0.1% | 0.15% | 0.2% |
---|---|---|---|---|---|
Foaming capacity/mL | 940 | 840 | 750 | 680 | 540 |
Half-life/s | 450 s | 21 min | 65 min | 2 h 27 min | 3 h 41 min |
Concentration of Y (Mass Fraction) | 0 | 0.05% | 0.1% | 0.15% | 0.2% | 0.25% | 0.3% | 0.35% | 0.4% |
---|---|---|---|---|---|---|---|---|---|
Foam volume/mL | 940 | 990 | 1020 | 1030 | 1030 | 1040 | 1000 | 980 | 950 |
Half-life/s | 450 | 515 | 555 | 715 | 1080 | 1200 | 765 | 840 | 730 |
Imported Foam | Domestic Foam | New Foam | |
---|---|---|---|
Foam volume Vf/mL | 2000 | 2000 | 2000 |
Volume of the foam agent solution Vl/mL | 120 | 170 | 190 |
Foaming rate ER/times | 16.7 | 11.7 | 10.5 |
Half-life | 14 min 32 s | 8 min 10 s | 7 min 35 s |
Particle Size Interval (µm) | Imported Foam | Domestic Foam | New Foam | |||
---|---|---|---|---|---|---|
Interval Distribution (%) | Cumulative Distribution (%) | Interval Distribution (%) | Cumulative Distribution (%) | Interval Distribution (%) | Cumulative Distribution (%) | |
1.00–10.92 | 7.52 | 7.52 | 3.01 | 3.01 | 0.27 | 0.27 |
10.92–20.83 | 22.65 | 30.18 | 1.34 | 4.36 | 0.61 | 0.88 |
20.83–30.75 | 24.95 | 55.13 | 0 | 4.36 | 10.36 | 11.24 |
30.75–40.67 | 22.84 | 77.96 | 0 | 4.36 | 8.42 | 19.66 |
40.67–50.58 | 15.83 | 93.8 | 0 | 4.36 | 2.83 | 22.49 |
50.58–60.50 | 2.26 | 96.06 | 0 | 4.36 | 15.9 | 38.38 |
60.50–70.42 | 3.94 | 100 | 0 | 4.36 | 26.55 | 64.93 |
70.42–80.33 | 0 | 100 | 95.64 | 100 | 14.61 | 79.54 |
80.33–90.25 | 0 | 100 | 0 | 100 | 20.46 | 100 |
90.25–100.17 | 0 | 100 | 0 | 100 | 0 | 100 |
100.17–110.08 | 0 | 100 | 0 | 100 | 0 | 100 |
110.08–120.00 | 0 | 100 | 0 | 100 | 0 | 100 |
Modifier | Mixing Test | Friction Coefficient Test | Adhesion Resistance Test | Slump Test | Direct Shear Test | |||||
---|---|---|---|---|---|---|---|---|---|---|
W (kW) | Rate of Change (%) | f | Rate of change (%) | F (N) | Rate of Change (%) | S (cm) | Rate of Change (%) | T (kPa) | Rate of Change (%) | |
New foam | 0.140 | −65.0% | 0.34 | −26.7% | 21.36 | −41.5.0% | 16 | −5.9% | 97.96 | −30.8% |
Domestic foam | 0.137 | −80.0% | 0.31 | −35.0% | 24.01 | −34.2% | 20 | 17.6% | 86.9 | −38.6% |
Imported foam | 0.135 | −90.0% | 0.29 | −39.0% | 23.42 | −35.8% | 23 | 35.3% | 109.2 | −23.0% |
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Sun, Y.; Liu, D.; Wang, G. Experimental Study on the Effects of New Foam on the Improvement of Sandy Soil for Earth Pressure Balance Shield. Buildings 2023, 13, 682. https://doi.org/10.3390/buildings13030682
Sun Y, Liu D, Wang G. Experimental Study on the Effects of New Foam on the Improvement of Sandy Soil for Earth Pressure Balance Shield. Buildings. 2023; 13(3):682. https://doi.org/10.3390/buildings13030682
Chicago/Turabian StyleSun, Yongshuai, Dapeng Liu, and Guihe Wang. 2023. "Experimental Study on the Effects of New Foam on the Improvement of Sandy Soil for Earth Pressure Balance Shield" Buildings 13, no. 3: 682. https://doi.org/10.3390/buildings13030682