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Using Triaxial Tests to Determine the Shearing Strength of Geogrid-Reinforced Sand

Šarūnas Skuodis
Šarūnas Skuodis
, 
Neringa Dirgėlienė
Neringa Dirgėlienė
 and 
Jurgis Medzvieckas
Jurgis Medzvieckas
   | Sep 25, 2020
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Article Category: Original Study
Published Online: Sep 25, 2020
Page range: 341 - 354
Received: Mar 16, 2020
Accepted: Jul 16, 2020
DOI: https://doi.org/10.2478/sgem-2020-0005
Keywords
© 2020 Šarūnas Skuodis et al., published by Sciendo
This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

Figure 1

Granulometric curve of the investigated soil.
Granulometric curve of the investigated soil.

Figure 2

Sample reinforcement with geogrid: left – flexible Basetrac® Grid PP 40 geogrid; middle – flexible Basetrac® Grid PET 40 geogrid; right – rigid Secugrid 40/40 Q1 geogrid.
Sample reinforcement with geogrid: left – flexible Basetrac® Grid PP 40 geogrid; middle – flexible Basetrac® Grid PET 40 geogrid; right – rigid Secugrid 40/40 Q1 geogrid.

Figure 3

Sample failure shape (from left to right): unreinforced; reinforced with Basetrac® Grid PP 40 geogrid; reinforced with Basetrac® Grid PET 40 geogrid; reinforced with Secugrid 40/40 Q1 geogrid.
Sample failure shape (from left to right): unreinforced; reinforced with Basetrac® Grid PP 40 geogrid; reinforced with Basetrac® Grid PET 40 geogrid; reinforced with Secugrid 40/40 Q1 geogrid.

Figure 4

Dependence of stress deviator on the vertical strain of unreinforced and reinforced soil samples with geogrids when the cell pressure σ3 = 100 kPa.
Dependence of stress deviator on the vertical strain of unreinforced and reinforced soil samples with geogrids when the cell pressure σ3 = 100 kPa.

Figure 5

Dependence of stress deviator on the vertical strain of unreinforced and reinforced soil samples with geogrids when the cell pressure σ3 = 200 kPa.
Dependence of stress deviator on the vertical strain of unreinforced and reinforced soil samples with geogrids when the cell pressure σ3 = 200 kPa.

Figure 6

Dependence of stress deviator on the vertical strain of unreinforced and reinforced soil samples with geogrids when the cell pressure σ3 = 300 kPa.
Dependence of stress deviator on the vertical strain of unreinforced and reinforced soil samples with geogrids when the cell pressure σ3 = 300 kPa.

Figure 7

Basetrac® Grid PET 40 geogrid condition: left – geogrid without damages before test; right – geogrid damages after test.
Basetrac® Grid PET 40 geogrid condition: left – geogrid without damages before test; right – geogrid damages after test.

Figure 8

Distribution of stress deviator in vertical cross section when the cell pressure σ3 = 100 kPa: left – unreinforced sample; middle – sample reinforced with Basetrac® Grid PP 40 geogrid; right – sample reinforced with Basetrac® Grid PET 40 geogrid.
Distribution of stress deviator in vertical cross section when the cell pressure σ3 = 100 kPa: left – unreinforced sample; middle – sample reinforced with Basetrac® Grid PP 40 geogrid; right – sample reinforced with Basetrac® Grid PET 40 geogrid.

Figure 9

Distribution of stress deviator in the horizontal plane at the geogrid position when the cell pressure σ3 =100 kPa: left – unreinforced sample; middle – sample reinforced with Basetrac® Grid PP 40 geogrid; right – sample reinforced with Basetrac® Grid PET 40 geogrid.
Distribution of stress deviator in the horizontal plane at the geogrid position when the cell pressure σ3 =100 kPa: left – unreinforced sample; middle – sample reinforced with Basetrac® Grid PP 40 geogrid; right – sample reinforced with Basetrac® Grid PET 40 geogrid.

Figure 10

Distribution of tension forces along axis 1 in the geogrids when the cell pressure σ3 = 300 kPa: left – sample reinforced with Basetrac® Grid PP 40 geogrid; right – sample reinforced with Basetrac® Grid PET 40 geogrid.
Distribution of tension forces along axis 1 in the geogrids when the cell pressure σ3 = 300 kPa: left – sample reinforced with Basetrac® Grid PP 40 geogrid; right – sample reinforced with Basetrac® Grid PET 40 geogrid.

Figure 11

Distribution of shear forces in the geogrids when the cell pressure σ3 = 300 kPa: left – sample reinforced with Basetrac® Grid PP 40 geogrid; right – sample reinforced with Basetrac® Grid PET 40 geogrid.
Distribution of shear forces in the geogrids when the cell pressure σ3 = 300 kPa: left – sample reinforced with Basetrac® Grid PP 40 geogrid; right – sample reinforced with Basetrac® Grid PET 40 geogrid.

Figure 12

Distribution of total volumetric strains εv when the cell pressure σ3 = 100 kPa: left – unreinforced sample; middle – sample reinforced with Basetrac® Grid PP 40 geogrid; right – sample reinforced with Basetrac® Grid PET 40 geogrid.
Distribution of total volumetric strains εv when the cell pressure σ3 = 100 kPa: left – unreinforced sample; middle – sample reinforced with Basetrac® Grid PP 40 geogrid; right – sample reinforced with Basetrac® Grid PET 40 geogrid.

Figure 13

Distribution of total volumetric strains εv when the cell pressure σ3 = 300 kPa: left – unreinforced sample; middle – sample reinforced with Basetrac® Grid PP 40 geogrid; right – sample reinforced with Basetrac® Grid PET 40 geogrid.
Distribution of total volumetric strains εv when the cell pressure σ3 = 300 kPa: left – unreinforced sample; middle – sample reinforced with Basetrac® Grid PP 40 geogrid; right – sample reinforced with Basetrac® Grid PET 40 geogrid.

Density of investigated samples.

SampleDensity, g/cm3
Unreinforced1.72–1.73
Basetrac® Grid PP 401.67–1.69
Secugrid 40/40 Q11.69–1.70
Basetrac® Grid PET 401.69–1.72

The main properties of flexible and rigid geogrids (taken from the technical brochures of suppliers).

PropertiesBasetrac® Grid PP 40Secugrid 40/40 Q1Basetrac® Grid PET 40
Nominal tensile strength (machine direction), nominal tensile strength (cross-machine direction)≥40 kN/m≥40 kN/m≥40 kN/m
Strain at nominal tensile strength7%7%10%
DurabilityPredicted to be durable for a minimum of 100 years in natural soils with 4 ≤ pH ≤ 9 and soil temperatures ≤25 C if covered within 30 days after installationPredicted to be durable for a minimum of 100 years in natural soils with 4 ≤ pH ≤ 9 and soil temperatures ≤25 C if covered within 30 days after installationPredicted to be durable for a minimum of 100 years in natural soils with 4 ≤ pH ≤ 9 and soil temperatures ≤25 C if covered within 30 days after installation

Unreinforced and reinforced soil with geogrid shearing strength.

Peak strength
Test conditionsCell pressure σ3, kPaMax stress deviator σ1–σ3, kPaVertical strain ɛ, %Angle of internal friction ϕ′, °Cohesion c′ kPaShearing strength ratio (reinforced/unreinforced)
Unreinforced104.54380.671.581040.770.00-
202.98627.851.5758-
305.391202.453.4799-
Basetrac® Grid PP 40106.68484.873.323442.2822.821.31
204.78966.783.46151.31
305.301308.824.42831.12
Secugrid 40/40 Q1106.20521.383.003339.7843.471.43
205.65916.873.32321.31
305.131233.043.63461.09
Basetrac® Grid PET 40107.01526.763.317141.9020.271.32
206.10908.435.06381.27
306.441328.614.11521.11

Simulated unreinforced and reinforced soil shearing strength with PLAXIS 3D.

Test conditionsExperimental resultsSimulation
Cell pressure σ3, kPaMax stress deviator σ1–σ3, kPaCell pressure σ3, kPaMax stress deviator σ1–σ3, kPa
Unreinforced104.54380.67100.0365.0
202.98627.85200.0740.0
305.391202.45300.01110.0
Basetrac® Grid PP 40106.68484.87100.0470.0
204.78966.78200.0960.0
305.301308.82300.01410.0
Basetrac® Grid PET 40107.01526.76100.0510.0
206.10908.43200.0910.0
306.441328.61300.01460.0
eISSN:
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Language:
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Journal Subjects:
Geosciences, other, Materials Sciences, Composites, Porous Materials, Physics, Mechanics and Fluid Dynamics
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