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MSE, BARIPADA
DEPARTMENT OF CIVIL ENGINEERING
PRESENTATION
ON
SPECIFIC GRAVITY
BY :- ER. ANKIT JOSHI
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Specific Gravity
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Specific Gravity Gs
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Phase Material
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The Mineral Skeleton
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Three Phase Diagram
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Fully Saturated Soils
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Dry Soils
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Partly Saturated Soils
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Phase Diagram
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Objectives of a Phase Diagram
To compute the weights (or masses) and volumes of the three different phases.
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Volume Relationships
Void ratio (e): is a measure of the void volume
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Volume Relationships
Porosity (n): is also a measure of the void volume, expressed as a percentage.
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Volume Relationships
Degree of saturation (S): is the percentage of the void volume filled by water.
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Weight Relationships
Water content (w): is a measure of the water
present in the soil.
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Unit Weight Relationships
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Unit Weight Relationships
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Phase Relations
Consider a fraction of the soil where Vs = 1.
The other volumes can
be obtained from the
previous definitions.
The weights can be obtained from:
Weights = Unit Weights x Volume
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Phase Relations
From the previous definitions,
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Phase Relations
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Definitions
Bulk (natural), saturated, dry and submerged
densities (ρ) are defined in a similar manner.
Here, you can also use mass (kg) instead of weight (kN).
γ / g = ρ = M/V
Where:
γ =N/m3 , g= m/s2, ρ = kg/m3
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Specific Gravity
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Specific Gravity, In Terms of Density
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Relationship between parameters
These definitions can be used to determine any desired relationships between above quantities, and hence to determine void ratio, degree of saturation, etc. That can not be measured directly by laboratory tests. Some relationships are as follows:
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Relationship between parameters
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A Gentle Reminder
Try not to memorize the equations. Understand
the definitions, and develop the relations from the phase diagram with VS = 1;
Assume GS ( 2.6-2.8) when not given;
Do not mix densities and unit weights;
Soil grains are incompressible. Their mass and volume remain the same at any void ratio.