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1. COMPOSITION OF SOIL

2. COMPOSITION OF SOIL
Soil deposit
consists of solid particles
and void spaces between
particles, either partially
or completely filled with
water.

3. COMPOSITION OF SOIL
The properties of soil deposit, especially the
strength and compressibility is necessary to determine
so that we can know the bearing capacity and it’s
stability when it is used for concrete.

4. COMPOSITION OF SOIL
The strength and compressibility of the soil is
directly related to:
- Soil Density
- Water content of soil
- Void ratio
- Degree of Saturation

5. RELATIONSHIP BETWEEN VOLUME AND WEIGHT

6. Total Weight
- It is equal to the weight of the solid + Weight of the
water.
Wt = Ws + Ww
Similarly ; for mass measurement;
Mt = Ms + Mw

7. For total volume:
Vt = Vs + Va + Vw
since : Volume of Voids (Vv) = Va + Vw
Therefore:
Vt = Vs + Vv

8. The relationship between the weight and volume:
W = Vg Uw
While Mass and Volume:
M= Vg Dw
Where:
W = Weight of the material (solid, liquid or gas)
V = Volume occupied by the material
Uw = Unit weight of water at 40
M = Mass of Materials
Dw = Density of water

9. SPECIFIC GRAVITY
- The Specific Gravity of most commonly occurring
rock or soil or soil materials is between 2.30 and
3.10.
- The Specific Gravity of soil solids lies within the range
of 2.60 to 2.75.

10. MATERIAL SPECIFIC GRAVITY
Borax 1.7
Iron oxide 5.3
Quartz 2.65
Feldspar 2.55-2.75
Other soil 2.6-2.7

11. UNIT WEIGHT OF SOIL (U)
Wet Unit Weight (Uwet)
- Which varies between limits that are fixed by the dry
unit weight and by the unit weight when the soil is
saturated with water.
Uwet = Wt
Vt

12. UNIT WEIGHT OF SOIL (U)
Dry Unit Weight (Udry)
- which is the unit weight of a soil when all void spaces
of the soil are completely filled with air, with no water.
Uwet = Ws
Vt

13. SOIL DENSITY(D)
Wet Density
- is the ratio of the total mass of soil to its total
volume
Dwet = Mt
Vt

14. SOIL DENSITY
Dry Density
-Dry density is used because it is esentially a
"normalized" density value.
Dwet = Mt
Vt

15. WATER CONTENT
- It is the ratio of the weight of water in soil volume to
the weight of the soil solids, or of the mass of water
in a soil to the mass of solid.
W% = Ww or Mw
Ws Ms
Where:
W% = Water content in percentage
Ww= Weight of Water
Ws= Weight of dry soil
Mw= Mass of water
Ms= Mass of Solid

16. VOID RATIO
- It is the convinient measure of a soil dry density that
is not affected by the specific gravity of the soilo
particle or by moisture content .
e = Volume of Voids (Vv)
Volume of Solid (Vs)

17. POROSITY
- describes the fraction of void space in the material,
where the void may contain, for example, air or water
P% = Volume of Voids * 100%
Total Volume

18. RELATIONSHIP BETWEEN VOID RATION
AND POROSITY
e= pVt
__100%__
Vt – pVt
100%
Therefore:
e= p%
_100%__
1 – p%
100%
DERIVATION
e = Vv
(Vs)
e = pVt
__100%__
Vt – Vv
e = p%
__100%__
1 – p%
100%
When: Vv= p% (Vt)
100%

19. RELATIONSHIP BETWEEN VOID RATION
AND POROSITY
p % = __e__ *100%
1 + e
When:
Vv= eVs
Vs = Vt - Vv
DERIVATION
p %= __eVs__ *100%
Vs + Vv
p % = _e(Vt-Vv)*100%
(Vt- Vv) + eVs
P%= _____e(Vt-Vv)____*100%
(Vt- Vv) + e(Vt-Vv)
Therefore:
p % = __e__ *100%
1 + e

20. DEGREE OF SATURATION
- Indicates the porton of the void spaces in a soil
material that is filled with water
S% = Vw * 100%
Vv

21. PROBLEM#1
One cubic foot of soil
sample weighing 130 lbs.
was taken from the test pit.
The entire sample is
throughly dried and finally
weighted 120 lbs. Solve for
the water content, wet unit
weight and the dry unit
weight
Block Diagram

22. Given:
Ws= 120
Wt= 130
Vt= 1 cu. Ft
For water content:
w% = Ww * 100% = 130-120 *100%
Ws 120
w%= 8.3%

23. For Wet Unit Weight
Uwet = Wt = 130
Vt 1.0
Uwet = 130 lbs/ cu. ft
For Dry Unit Weight
Udry = Ws = 120
Vt 1.0
Udry= 120 lbs/ cu. ft

24. PROBLEM#2
Compute for the wet
density, dry unit weight,
void ratio, water
contentand the degree of
saturation from a sample
of moist soil with mass
weight of 20 kg that
occupies a total volume of
0.008 cu. M. and 0.006
cu.m volume of solid. The
sample is dried in oven
and weighted 18 kg. The
specific gravity of the soil
solid is 2.60
Block Diagram

25. For wet density:
Dwet = Mt = 20
Vt 0.008
Dwet= 2500 kg/cu.m
For dry unit weight:
Udry= Ws = Msg = 18 kg (9.81 kN/ cu. m)
Vt Vt 0.008 cu.m
Udry= 202.072 kN/cu.m

26. For water content:
w%= Mw * 100 = (20-18) * 100
Ms 18
w%= 11.1%
For Void Ratio:
e= Vv = 0.008 – 0.006
Vs 0.006
e= 0.33

27. For Degree of Saturation:
S% = Wgs = 11.1 * 2.60
e 0.33
S % = 87%

28. SUBMERGED SOIL
For under water condition, the solid is buoyed up by pressure of the
surrounding body of water. Therefore the weight of submerged soil,
become lighter compared with the soil above water. Thus the
effective soil weight becomes the unit weight when weighed under
water, the weight of water in the voids of soil is zero when
submerged, because all voids were assumed to be filled with and the
weight of the solid reduced by the weight of water displaces
Wsub = Vs gs Uw - Vs gw Uw
= Vs Uw ( gs – gw)
Wsub = Vs Uw (gs – 1)