Geotechnical Engineering

DHARM

COMPOSITION OF SOIL TERMINOLOGY AND DEFINITIONS 27

Vs =

WW

G

s

s

s

γγw

==

. ×

210

26 001

= 80.77 cm^3

Vv = (V – Vs) = (150 – 80.77) = 69.23 cm^3

Degree of saturation, S =

V

V

w
v
S = 40/69.23 = 0.578
∴ S = 40/69.23 = 0.578
∴ Degree of saturation = 57.8%
Thus, it may be observed that it may sometimes be simpler to solve numerical problems
by the use of the soil-phase diagram.
Note. All the illustrative examples may be solved with the aid of the soil-phase diagram or the
unit-phase diagram also ; however, this may not always be simple.

Summary of Main Points

1. Soil is a complex physical system ; generally speaking, it is a three-phase system, mineral grains
   of soil, pore water and pore air, constituting the three phases. If one of the phases such as pore
   water or pore air is absent, it is said to be dry or saturated in that order ; the system then reduces
   to a two-phase one.


2. Phase-diagram is a convenient representation of the soil which facilitates the derivation of use-
   ful quantitative relationships involving volumes and weights.
   Void ratio, which is the ratio of the volume of voids to that of the soil solids, is a useful concept in
   the field of geotechnical engineering in view of its relatively invariant nature.


3. Submerged unit weight is the difference between saturated unit weight and the unit weight of
   water.


4. Specific gravity of soil solids or grain specific gravity occurs in many relationships and is one of
   the most important values for a soil.

References

1. Alam Singh & B.C. Punmia : Soil Mechanics and Foundations, Standard Book House, Delhi-6,
   1970.


2. A.R. Jumikis : Soil Mechanics, D. Van Nostrand Co., Princeton, NJ, USA, 1962.


3. T.W. Lambe and R.V. Whitman : Soil Mechanics, John Wiley & Sons, Inc., NY, 1969.


4. D.F. McCarthy : Essentials of Soil Mechanics and Foundations, Reston Publishing Company,
   Reston, Va, USA, 1977.


5. V.N.S. Murthy : Soil Mechanics and Foundation Engineering, Dhanpat Rai and Sons, Delhi-6,
   2nd ed., 1977.


6. S.B. Sehgal : A Text Book of Soil Mechanics, Metropolitan Book Co., Ltd., Delhi, 1967.


7. G.N. Smith : Essentials of Soil Mechanics for Civil and Mining Engineers, Third Edition, Metric,
   Crosby Lockwood Staple, London, 1974.