1. SOIL COMPOSITION
-Ms Ikmalzatul

2. Soil: A 3-Phase Material
Air
Water
Solid

3. The Mineral Skeleton
Solid Particles
Volume
Voids (air or water)

4. Three Phase Diagram Air Water Solid Idealization: Mineral Skeleton

5. Fully Saturated Soils
Water
Solid
Mineral Skeleton
Fully Saturated

6. Dry Soils
Air
Solid
Dry Soil
Mineral Skeleton

7. Partly Saturated Soils
Solid
Air
Water
Mineral Skeleton
Partly Saturated Soils

8. Three Phase System Air Water Solid Volume Weight Va Wa~0 Vv Vw Ww WTVT Vs Ws
Volume
Weight

9. Weight Relationships Weight Components: Weight of Solids = Ws
Weight of Water = Ww
Weight of Air ~ 0

10. Volumetric Relationships
Volume Components:
Volume of Solids = Vs
Volume of Water = Vw
Volume of Air = Va
Volume of Voids = Va + Vw = Vv

11. Volumetric Relationships
Volume Components:
Volume of Solids = Vs
Volume of Water = Vw
Volume of Air = Va
Volume of Voids = Va + Vw = Vv

12. Specific Gravity Unit weight of Water, w
w = 1.0 g/cm3 (strictly accurate at 4° C)
w = 62.4 pcf
w = 9.81 kN/m3

13. Specific Gravity Iron 7.86 Aluminum 2.55-2.80 Lead 11.34 Mercury 13.55
Granite 2.69
Marble 2.69
Quartz 2.60
Feldspar

14. Specific Gravity, Gs

15. Example: Volumetric Ratios
Determine void ratio, porosity and degree of saturation of a soil core sample
Data:
Weight of soil sample = 1013g
Vol. of soil sample = 585.0cm3
Specific Gravity, Gs = 2.65
Dry weight of soil = 904.0g

16. Example Air Water Solid Wa~0 134.9cm3 W =1.00 243.9cm3 109.0g
Volumes
Weights

17. Example Air Water Solid 134.9cm3 W =1.00 243.9cm3 109.0cm3 585.0cm3
Volumes
s =2.65
341.1cm3
109.0cm3
243.9cm3
134.9cm3
W =1.00

18. Soil Unit weight (kN/m3)
Bulk (or Total) Unit weight
 = WT / VT
Dry unit weight
d = Ws / VT
Buoyant (submerged) unit weight
b = - w

19. Typical Unit weights

20. THE END