Introduction
Materials and Method
Soil Properties
Soil properties | Values |
---|---|
Liquid limit (%) | 79.2 |
Plastic limit (%) | 33.2 |
Plasticity index (%) | 46 |
Soil classification (USCS) | CH |
Optimum moisture content (OMC, %) | 26.7 |
Maximum dry density (MDD, g/cm3) | 1.35 |
Specific gravity | 2.71 |
Hydraulic conductivity (m/day) | 1.18 × 10–4 |
Geosynthetics Properties
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GS1: non-woven geosynthetic is a highly porous material that allows water to pass through while preventing soil migration. It provides excellent filtration, and it is commonly used in the construction of roads, railways, and embankments where the ground is soft and unstable.
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GS2: woven geosynthetic that is commonly used as the dewatering system for a range of engineering applications including ground stabilization, railroad support, and aggregate separation (Fig. 2a).
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GS3: geogrid can be used for aggregates and soil stabilization, and it is primarily used in railways and road works for pavement reinforcement (Fig. 2b). In this study, GS3 was combined with the GS1 to increase the stiffness of the non-woven geosynthetic which may result in improvement in the load carrying capacity of the soil [24].
Geosynthetics | Geosynthetic type | Thickness (mm) | Ultimate tensile strength, (kN/m) | Pore size distribution, O95, micron | Flow rate, (l/m2/s) | |
---|---|---|---|---|---|---|
MD | CMD | |||||
GS1 | Non-woven | 3 | 26.5 | 23 | 75 | 135 |
GS2 | Woven | 1.8 | 78.8 | 109.4 | 195 | 13.55 |
GS3 | Geogrid | 2 | 390 | – | N/A | N/A |
California Bearing Ratio (CBR)
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Soil (without geosynthetics).
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Soil with GS1 combined with GS3.
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Soil with GS2.
Soil Column Equipment
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MP 306 Moisture Probe which has a range of 0–100% and an accuracy of ± 2%.
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Suction Sensor used were Meter Teros-21, which has a range of – 9 kPa to – 2000 kPa with an accuracy of ± 10%. It also measures the temperature of the soil with a range of − 40 to + 60 °C, with an accuracy of ± 1 °C.
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Panasonic HG-C1100 Digital Laser sensor were used for measuring the vertical displacement (L1 and L2). The sensor has a range of ± 35 mm from an initial measuring distance of 100 mm with an accuracy of 70 μm.
Sample Preparation
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Test 1: Non-reinforced soil.
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Test 2: Soil with a single layer of GS1 supported by GS3.
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Test 3: Soil with a single layer of GS2
Column Test Procedure
Day | 1 | 2 | 3 | 4 | 5 | 6 | Total |
---|---|---|---|---|---|---|---|
Total precipitation during 2011 rainfall event, mm | 68 | 17 | 23 | 5 | 84 | 123 | 320 |
Water introduced to soil column, l | 6.1 | 1.5 | 2.1 | 0.5 | 7.6 | 11.0 | 28.8 |
Results and Discussion
CBR Test Results
No. | Experimental condition | Average CBR value |
---|---|---|
1 | Soil | 1.62 |
2 | GS1 combined with GS3 | 1.67 |
3 | GS2 | 1.19 |
Soil Column Experiment Results
Soil Column Tests with Geosynthetics
Soil Mass Swell
Conclusions
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Both types of geosynthetics did not improve the CBR of the studied soil. The CBR values obtained for the reinforced and non-reinforced soil were below 2, which can be attributed to extremely high plasticity of the tested soil.
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Both types of geosynthetics were effective in reducing the total vertical displacement (swell) of the soil mass. The non-woven geosynthetic combined with geogrid provided a greater reduction in vertical swell due to higher flow rate of the material compared to the woven geosynthetic and non-reinforced soil.
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The reduction in total vertical swell of the soil was directly related to the degree of saturation (S) of the soil mass. When the soil reached a high value of S (80–85%) after the initial wetting phase, the rate of vertical swell significantly decreased which cause a lower swell rate for the remainder of the experiment.
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The geosynthetic materials used in this study produced better drainage conditions for the soil mass compared to non-reinforced soil. This limited the time of soil–water interaction in the top part of the soil mass resulting in a lower vertical swell observed from the tests.