Post on 21-Dec-2014
description
Basic Definitions and Terminology
• Soil is generally a three phase material• Contains solid particles and voids• Voids can contain liquid and gas phases
Solid
Water
Air Vs
Vw
Va
• Soil is generally a three phase material• Contains solid particles and voids• Voids can contain liquid and gas phases
Solid
Water
Air Vs
Vw
Va
• Soil is generally a three phase material• Contains solid particles and voids• Voids can contain liquid and gas phases
Solid
Water
Air
Phase Volume Mass Weight
Air Va 0 0
Water Vw Mw Ww
Solid Vs Ms Ws
Vs
Vw
Va
Units
• Length metres• Mass tonnes (1 tonne = 103 kg)• Density t/m3
• Weight kilonewtons (kN)• Stress kilopascals (kPa) 1 kPa= 1 kN/m2
• Unit weight kN/m3
• Accuracy Density of water, w = 1 t/m3
Stress/Strength to 0.1 kPa
Weight and Unit weight
• Force due to mass (weight) more important than mass• W = M g
• Unit weight
Weight and Unit weight
• Force due to mass (weight) more important than mass• W = M g
• Unit weight
= g
Weight and Unit weight
• Force due to mass (weight) more important than mass• W = M g
• Unit weight
= g
vz v = g z
v = z
Specific Gravity
• Gs 2.65 for most soils
• Gs is useful because it enables the volume of solid particles to be calculated from mass or weight
GD e n s i t y o f M a t e r i a l
D e n s i t y o f W a t e r w
GU n i t W e i g h t o f M a t e r i a l
U n i t W e i g h t o f W a t e r w
This is defined by
Specific Gravity
• Gs 2.65 for most soils
• Gs is useful because it enables the volume of solid particles to be calculated from mass or weight
GD e n s i t y o f M a t e r i a l
D e n s i t y o f W a t e r w
GU n i t W e i g h t o f M a t e r i a l
U n i t W e i g h t o f W a t e r w
This is defined by
VM M
G
W W
Gs
s
s
s
s w
s
s
s
s w
Voids ratio• It is not the actual volumes that are important but rather the
ratios between the volumes of the different phases. This is described by the voids ratio, e, or porosity, n, and the degree of saturation, S.
Voids ratio• It is not the actual volumes that are important but rather the
ratios between the volumes of the different phases. This is described by the voids ratio, e, or porosity, n, and the degree of saturation, S.
• The voids ratio is defined as
Voids ratio• It is not the actual volumes that are important but rather the
ratios between the volumes of the different phases. This is described by the voids ratio, e, or porosity, n, and the degree of saturation, S.
• The voids ratio is defined as
• and the porosity as
Voids ratio• It is not the actual volumes that are important but rather the
ratios between the volumes of the different phases. This is described by the voids ratio, e, or porosity, n, and the degree of saturation, S.
• The voids ratio is defined as
• and the porosity as
The relation between these quantities can be simply determined as follows
Vs = V - Vv = (1 - n) V
Voids ratio• It is not the actual volumes that are important but rather the
ratios between the volumes of the different phases. This is described by the voids ratio, e, or porosity, n, and the degree of saturation, S.
• The voids ratio is defined as
• and the porosity as
The relation between these quantities can be simply determined as follows
Vs = V - Vv = (1 - n) V
Hence
Degree of Saturation• The degree of saturation, S, has an important influence on soil
behaviour• It is defined as
Degree of Saturation• The degree of saturation, S, has an important influence on soil
behaviour• It is defined as
• The phase volumes may now be expressed in terms of e, S and Vs
• Vw = e S Vs Va = Vv - Vw = e Vs (1 - S)
Degree of Saturation• The degree of saturation, S, has an important influence on soil
behaviour• It is defined as
• The phase volumes may now be expressed in terms of e, S and Vs
• Vw = e S Vs Va = Vv - Vw = e Vs (1 - S)
Assuming Vs = 1 m3, the following table can be produced
Phase Volume Mass Weight
Air e (1 - S) 0 0
Water e S e S w e S w
Solid 1 G s w G s w
Unit Weights
• The bulk unit weight
Unit Weights
• The bulk unit weight
• The saturated unit weight (S = 1)
Unit Weights
• The bulk unit weight
• The saturated unit weight (S = 1)
• The dry unit weight (S = 0)
Unit Weights
• The bulk unit weight
• The saturated unit weight (S = 1)
• The dry unit weight (S = 0)
• The submerged unit weight
Moisture Content
• The moisture content, m, is defined as
Moisture Content
• The moisture content, m, is defined as
In terms of e, S, Gs and w
Ww = wVw = we S Vs
Ws = s Vs = w Gs Vs
Moisture Content
• The moisture content, m, is defined as
In terms of e, S, Gs and w
Ww = wVw = we S Vs
Ws = s Vs = w Gs Vs
hence
Example 1
Phase Trimmings Mass
(g)
Sample Mass, M
(g)
Sample Weight, Mg
(kN)
Total 55 290 2845 10-6
Solid 45 237.3 2327.9 10-6
Water 10 52.7 517 10-6
• Distribution by mass and weight
Example 1
Phase Trimmings Mass
(g)
Sample Mass, M
(g)
Sample Weight, Mg
(kN)
Total 55 290 2845 10-6
Solid 45 237.3 2327.9 10-6
Water 10 52.7 517 10-6
• Distribution by mass and weight
• Distribution by volume (assume Gs = 2.65)
Total Volume V = r2 l
Example 1
Phase Trimmings Mass
(g)
Sample Mass, M
(g)
Sample Weight, Mg
(kN)
Total 55 290 2845 10-6
Solid 45 237.3 2327.9 10-6
Water 10 52.7 517 10-6
• Distribution by mass and weight
• Distribution by volume (assume Gs = 2.65)
Total Volume V = r2 l
Water Volume
Example 1
Phase Trimmings Mass
(g)
Sample Mass, M
(g)
Sample Weight, Mg
(kN)
Total 55 290 2845 10-6
Solid 45 237.3 2327.9 10-6
Water 10 52.7 517 10-6
• Distribution by mass and weight
• Distribution by volume (assume Gs = 2.65)
Total Volume V = r2 l
Water Volume
Solids Volume
Example 1
Phase Trimmings Mass
(g)
Sample Mass, M
(g)
Sample Weight, Mg
(kN)
Total 55 290 2845 10-6
Solid 45 237.3 2327.9 10-6
Water 10 52.7 517 10-6
• Distribution by mass and weight
• Distribution by volume (assume Gs = 2.65)
Total Volume V = r2 l
Water Volume
Solids Volume
Air Volume Va = V - Vs - Vw
Moisture content
Moisture content
Voids ratio
Moisture content
Voids ratio
Degree of Saturation
Moisture content
Voids ratio
Degree of Saturation
Bulk unit weight
Moisture content
Voids ratio
Degree of Saturation
Bulk unit weight
Dry unit weight
Moisture content
Voids ratio
Degree of Saturation
Bulk unit weight
Dry unit weight
Saturated unit weight
Note that dry < bulk < sat
Example 2Volume and weight distributions
Phase Volume
(m3)
Dry Weight
(kN)
Saturated Weight
(kN)
Voids 0.7 0 0.7 9.81 = 6.87
Solids 1.0 2.65 9.81 = 26.0 26.0
Example 2Volume and weight distributions
Dry unit weight,
Phase Volume
(m3)
Dry Weight
(kN)
Saturated Weight
(kN)
Voids 0.7 0 0.7 9.81 = 6.87
Solids 1.0 2.65 9.81 = 26.0 26.0
Example 2Volume and weight distributions
Dry unit weight,
Saturated unit weight
Phase Volume
(m3)
Dry Weight
(kN)
Saturated Weight
(kN)
Voids 0.7 0 0.7 9.81 = 6.87
Solids 1.0 2.65 9.81 = 26.0 26.0
Example 2Volume and weight distributions
Dry unit weight,
Saturated unit weight
Moisture content (if saturated)
Phase Volume
(m3)
Dry Weight
(kN)
Saturated Weight
(kN)
Voids 0.7 0 0.7 9.81 = 6.87
Solids 1.0 2.65 9.81 = 26.0 26.0