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This reference soil is, composed by a matrix and inclusions (the ratio between the average size of the matrix (ds0,mat) nd that of the inclusions (ds0,inci), ds0,inci /ds0,mat Must be greater than 10 [12, 13] so that the matrix can be considered omogeneous in relation to the inclusions). Also, the inclusions are arranged randomly and are not in contact [13, 14] Ficure 1).

Figure 1 This reference soil is, composed by a matrix and inclusions (the ratio between the average size of the matrix (ds0,mat) nd that of the inclusions (ds0,inci), ds0,inci /ds0,mat Must be greater than 10 [12, 13] so that the matrix can be considered omogeneous in relation to the inclusions). Also, the inclusions are arranged randomly and are not in contact [13, 14] Ficure 1).

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Table 2. Characteristics of the sand used
Table 2. Characteristics of the sand used
Figure 2. Granulometric spread of the sand used The physical characteristics of the sand are listed in Table 2.
Figure 2. Granulometric spread of the sand used The physical characteristics of the sand are listed in Table 2.
Figure 3. View of the gravel: 10/20 mm gravel (a) and 4/60 mm gravel (b) The selected inclusions are natural gravels with density ps = 2.65 g/cm’, and a maximum diameter of 60 mm (Figure 2.2. Experimental Procedure
Figure 3. View of the gravel: 10/20 mm gravel (a) and 4/60 mm gravel (b) The selected inclusions are natural gravels with density ps = 2.65 g/cm’, and a maximum diameter of 60 mm (Figure 2.2. Experimental Procedure
Figure 4. Fabrication of a soil test specimen The specimens are made by compacting the material in successive layers of ten layers of soil, each 6 cm thick (Figure 2.3. Experimental Program
Figure 4. Fabrication of a soil test specimen The specimens are made by compacting the material in successive layers of ten layers of soil, each 6 cm thick (Figure 2.3. Experimental Program
Figure 6. The typical test performed on pure sand (In=0.8% and o'.=100kPa): (a) shear curve; (b) volumetric deformation curve
Figure 6. The typical test performed on pure sand (In=0.8% and o'.=100kPa): (a) shear curve; (b) volumetric deformation curve
From these tests (Figures 7 and 8), we define the repeatability spindle (the envelope of the curves corresponding to these tests). This spindle for fv = 20 % will be used thereafter and will make it possible to conclude on the influence of the fundamental parameters on the behavior of the studied coarse soils.
From these tests (Figures 7 and 8), we define the repeatability spindle (the envelope of the curves corresponding to these tests). This spindle for fv = 20 % will be used thereafter and will make it possible to conclude on the influence of the fundamental parameters on the behavior of the studied coarse soils.
Figure 8. Repeatability tests on pure sand (In=0.8% and o'=100kPa)
Figure 8. Repeatability tests on pure sand (In=0.8% and o'=100kPa)
Figure 9. Influence of the volume proportion of gravel fv: (a) shear curves; (b) volumetric deformation curves (G 30/60mm, In=0.8% and o'.=100kPa)
Figure 9. Influence of the volume proportion of gravel fv: (a) shear curves; (b) volumetric deformation curves (G 30/60mm, In=0.8% and o'.=100kPa)
Figure 11. Grain contact areas during the triaxial test: (a) fv = 12%; (b) fv = 35% An increase in the deviator at failure with the proportion of inclusions is observed (Figure 9-a). The softening phas« is more significant than the proportion fv is high. We also notice a "ductile" behavior for the pure sand with rupture reached for deformation of 8%, to a "fragile" behavior for the sand-gravel mixture with a peak of resistance reached fo deformation of 2%. These observations can be explained by the fact that with the increase of fv, the contact betwee gravels becomes more important contributing to the reinforcement of the soil [17-19] (Figure 11). This forms during th: test a more shear-resistant surface.
Figure 11. Grain contact areas during the triaxial test: (a) fv = 12%; (b) fv = 35% An increase in the deviator at failure with the proportion of inclusions is observed (Figure 9-a). The softening phas« is more significant than the proportion fv is high. We also notice a "ductile" behavior for the pure sand with rupture reached for deformation of 8%, to a "fragile" behavior for the sand-gravel mixture with a peak of resistance reached fo deformation of 2%. These observations can be explained by the fact that with the increase of fv, the contact betwee gravels becomes more important contributing to the reinforcement of the soil [17-19] (Figure 11). This forms during th: test a more shear-resistant surface.
Regarding the volume deformations (Figure 9-b), the results obtained show that the soil becomes less dilatant by increasing the proportion of inclusions. The same observations for the tests carried out on the mixture of sand with gravel 10/20 mm (Figure 9). The same analysis has been established for soil with gravel G10/20mm and a compactness index ID =0.4% (Figure 12); from the point of view of volume deformation, we find a mainly contracting behavior.
Regarding the volume deformations (Figure 9-b), the results obtained show that the soil becomes less dilatant by increasing the proportion of inclusions. The same observations for the tests carried out on the mixture of sand with gravel 10/20 mm (Figure 9). The same analysis has been established for soil with gravel G10/20mm and a compactness index ID =0.4% (Figure 12); from the point of view of volume deformation, we find a mainly contracting behavior.
Figure 13. Influence of maximum gravel diameter dmax: (a) shear curves; (b) volumetric deformation curves (fv=20%, In=0.8% and o'-=100kPa)
Figure 13. Influence of maximum gravel diameter dmax: (a) shear curves; (b) volumetric deformation curves (fv=20%, In=0.8% and o'-=100kPa)
Concerning the granulometric spread, we first carried out a series of tests on specimens with 20% and 35% of gravel 10/20 mm, 30/60 mm, 10/60 mm and 4/60 mm with an ID=0.8%. Figures 16 and 17 synthesize the results obtained.
Concerning the granulometric spread, we first carried out a series of tests on specimens with 20% and 35% of gravel 10/20 mm, 30/60 mm, 10/60 mm and 4/60 mm with an ID=0.8%. Figures 16 and 17 synthesize the results obtained.
Figure 15. Influence of maximum gravel diameter dmax: (a) shear curves; (b) volumetric deformation curves (fv=12 %, In=0.8% and o'-=100kPa)
Figure 15. Influence of maximum gravel diameter dmax: (a) shear curves; (b) volumetric deformation curves (fv=12 %, In=0.8% and o'-=100kPa)
Figure 16. Influence of granulometric spread: (a) shear curves; (b) volumetric deformation curves (fv=20 %, In=0.8% and o'-=100kPa)
Figure 16. Influence of granulometric spread: (a) shear curves; (b) volumetric deformation curves (fv=20 %, In=0.8% and o'-=100kPa)
Figure 17. Influence of granulometric spread: (a) shear curves; (b) volumetric deformation curves (fv=35 %, In=0.8% and o'-=100kPa)
Figure 17. Influence of granulometric spread: (a) shear curves; (b) volumetric deformation curves (fv=35 %, In=0.8% and o'-=100kPa)
Figure 18. Influence of granulometric spread: (a) shear curves; (b) volumetric deformation curves (fv=20%, In=0.4% and o'-=100kPa)
Figure 18. Influence of granulometric spread: (a) shear curves; (b) volumetric deformation curves (fv=20%, In=0.4% and o'-=100kPa)
Figure 19. Rupture Mohr circles and intrinsic curve for a mixture with 10/20 mm inclusions and fv = 20%
Figure 19. Rupture Mohr circles and intrinsic curve for a mixture with 10/20 mm inclusions and fv = 20%
Table 3. Cohesion and friction angle values for a mixture with 10/20 mm inclusions
Table 3. Cohesion and friction angle values for a mixture with 10/20 mm inclusions
Figure 20. Evolution of the internal friction angle g' as a function of the volume proportion of gravel In order to synthesize and better analyze the results of the table, curves showing the evolution of the angle of internal friction of the different soils as a function of the proportion of gravel have been drawn (Figure 20).
Figure 20. Evolution of the internal friction angle g' as a function of the volume proportion of gravel In order to synthesize and better analyze the results of the table, curves showing the evolution of the angle of internal friction of the different soils as a function of the proportion of gravel have been drawn (Figure 20).
Table 4. Test characteristics showing the effect of sand density index ID on the shear strength qmas
Table 4. Test characteristics showing the effect of sand density index ID on the shear strength qmas
Figure 21. The evolution of qmax from a loose state to a dense state as a function of the volume fraction of the gravel It is clearly observed that the shear strength increases with the volume proportion of the inclusions in a similar way, and this independently of the compactness index Ip (Figure 21).
Figure 21. The evolution of qmax from a loose state to a dense state as a function of the volume fraction of the gravel It is clearly observed that the shear strength increases with the volume proportion of the inclusions in a similar way, and this independently of the compactness index Ip (Figure 21).
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