Physical and Numerical Models of Mechanically Stabilized Earth Walls Using Self-Fabricated Steel Reinforcement Grids Applied to Cohesive Soil in Vietnam
Abstract
:1. Introduction
2. Full-Scale Experimental Model
2.1. Model Design
2.1.1. Wall-Facing Panels
2.1.2. Backfill Material
2.1.3. Reinforcement
2.1.4. Ground Foundation
2.1.5. Loading System
2.2. Construction and Instrumentation of the MSE Wall
3. Numerical Modelling
- If z > z0 = 6 m;
- If z ≤ z0 = 6 m;
4. Results and Discussion
4.1. Full-Scale Model Results
4.1.1. MSE Wall Loading
4.1.2. Tensile Forces in the Reinforcement Bars
4.1.3. Failure Load
4.1.4. Lateral Displacement of the Wall Facing
4.2. Numerical Model Results
5. Conclusions
- The retaining wall suddenly collapsed due to internal instability (reinforcement rupture) at a load level of 302 kN/m2, which was 15 times greater than the design load. At that failure mode, the maximum lateral displacement at the top of the wall facing was 3899 µm, which was much less than the allowable displacement of the wall (3 cm). The failure surface within the reinforced soil block was similar to theoretical studies.
- It was noted that when the test load was lower than the design load (<20 kN/m2) the tensile forces in the deepest reinforcement layer showed the highest value. However, the upper reinforcement layers achieved the highest tensile forces when the test load increased. Thus, it is essential to enhance the bearing capacity of the reinforcement layers near the ground surface in special constructions with a very high surcharge load.
- The measured data from the full-scale model were validated by the numerical model using FLAC software. The tensile load distribution pattern in the reinforcement layer and the lateral displacement of the wall were similar to the research results from other studies and were in good agreement with the current standards.
- The experimental results also demonstrated that when using a self-fabricated galvanized steel reinforcement (CB300V; Φ 10) for the MSE wall, the wall maintained its stability under the applied load considering a metal loss of 65% of the initial tensile strength. Deformations to the reinforcement were minimal, and the wall was capable of withstanding high surcharge loads. Therefore, self-fabricated galvanized steel reinforcement grids and the specific soil material in the Danang area could be used as the reinforcement material for MSE walls with high stability.
Author Contributions
Funding
Institutional Review Board Statement
Informed Consent Statement
Data Availability Statement
Conflicts of Interest
Nomenclature
MSE walls | Mechanically stabilized earth walls |
GSG | Galvanized steel grid |
F0 | Initial tensile strength of the reinforcement |
ΔF | Proportional loss of tensile strength of the reinforcement |
La | Length of the reinforcement bars in the failure zone |
Le | Length of the reinforcement bars in the backfill zone |
f* | Apparent friction coefficient for the steel reinforcement and backfill interfaces |
Cu | Coefficient of uniformity of the backfill soil |
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Parameter | Unit | Value |
---|---|---|
Saturated density, γ | kN/m3 | 2.070 |
Dry density, γk | kM/m3 | 1.816 |
Friction angle, φsoil | Degrees | 34.3 |
Cohesion, csoil | Pa | 5100 |
Plasticity index, IP | - | 8.55 |
Uniformity coefficient, Cu | - | 45.6 |
pH | - | 5.9 |
Ion, Cl− | mg/g | 0.094 |
Ion, SO42− | mg/g | 0.497 |
Parameter | Unit | Value |
---|---|---|
Initial tensile strength of the steel reinforcement | N | 49,000 |
Loss of tensile strength | N | 17,150 |
Remaining tensile strength within the reinforcement | N | 31,850 |
Drilling the reinforcement bars to reduce their cross-sectional area | % | 26.6 |
Drilling depth (Φ 5) | mm | 8.1 |
Parameter | Unit | Value |
---|---|---|
Concrete panel | ||
Width | m | 0.75 |
Height | m | 0.15 |
Length | m | 1.5 |
Young’s modulus | Pa | 2 × 1011 |
Compressive strength of concrete | Pa | 35,000 |
Foundation soil | ||
Unit weight, γFound | kg/m3 | 2700 |
Friction angle, φFound | Degrees | 51 |
Cohesion, cFound | Pa | 5.51 × 107 |
Bulk modulus | Pa | 4.39 × 1010 |
Shear modulus | Pa | 3.02 × 1010 |
Backfill soil | ||
Unit weight, γsoil | kg/m3 | 2070 |
Friction angle, φsoil | Degrees | 34.3 |
Cohesion, csoil | Pa | 5100 |
Bulk modulus | Pa | 1.5 × 107 |
Shear modulus | Pa | 6 × 106 |
Steel reinforcement | ||
Length | m | 2.1 |
Steel bar thickness | m | 0.010 |
Calculation width | m | 1.5 |
Number of longitudinal bars per calculation width | Strip | 4 |
Young’s modulus | Pa | 2 × 1011 |
Tensile strength | N/m | 31,850 |
Tensile failure strain | % | 0.19 |
Shear stiffness | N/m2 | 2 × 107 |
Parameter | Unit | Value |
---|---|---|
Backfill soil: concrete panel | ||
Normal stiffness | Pa/m | 2.4 × 106 |
Shear stiffness | Pa/m | 2.4 × 106 |
Friction angle | Degrees | 26 |
Backfill soil: steel reinforcement | ||
Shear stiffness | N/m2 | 2 × 107 |
Cohesion | N/m | 1 × 105 |
Initial apparent friction coefficient | ||
Layer 4 | 1.917 | |
Layer 3 | 1.751 | |
Layer 2 | 1.586 | |
Layer 1 | 1.420 |
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Chau, T.-L.; Nguyen, T.-H.; Pham, V.-N. Physical and Numerical Models of Mechanically Stabilized Earth Walls Using Self-Fabricated Steel Reinforcement Grids Applied to Cohesive Soil in Vietnam. Appl. Sci. 2024, 14, 1283. https://doi.org/10.3390/app14031283
Chau T-L, Nguyen T-H, Pham V-N. Physical and Numerical Models of Mechanically Stabilized Earth Walls Using Self-Fabricated Steel Reinforcement Grids Applied to Cohesive Soil in Vietnam. Applied Sciences. 2024; 14(3):1283. https://doi.org/10.3390/app14031283
Chicago/Turabian StyleChau, Truong-Linh, Thu-Ha Nguyen, and Van-Ngoc Pham. 2024. "Physical and Numerical Models of Mechanically Stabilized Earth Walls Using Self-Fabricated Steel Reinforcement Grids Applied to Cohesive Soil in Vietnam" Applied Sciences 14, no. 3: 1283. https://doi.org/10.3390/app14031283