1. ENROLLMENT NO: STUDENT NAME: DARSHAN P MANANI NAREN H PATEL BRIJESH PRAJAPATI DHARMISTHA SOLANKI

2. GEOTECHNICS & APPLIED GEOLOGY
( )
TOPIC:
SOIL CLASSIFICATION & SOIL WATER

3. SOIL CLASSIFICATION OBJECTIVE OF SOIL CLASSIFICATION:
To arrange various types of soils into group according to their engineering or agricultural properties.
To decide the suitability of soil as a construction material for the construction of roads, earthen dams, embankment, etc.
To decide the suitability of soil for the foundation of structures.
A soil classification system provides a common language between engineers dealing with soils. It is useful in exchange of information and experience between the geotechnical engineers.

4. BASIC REQUIREMENTS OF SOIL CLASSIFICATION:
It should have a limited number of groups.
It should have scientific approach.
It should be simple and should use the terms which are easily understood.
The properties considered should have meaning for the engineering profession.
It should be acceptable to all engineers.

5. SOIL CLASSIFICATION SYSTEM:
For general engineering purposes, soils may be classifies by following systems.
Particle size classification
Textural classification
Unified soil classification
IS classification

6. Particle size classification:
The size of individual particles has an important influence on the behavior of soil. In the particle size classification, soils are designated according to the grain size or particle size.
These terms are use only as designation of particles size, and do not signify the naturally occurring soil types.
A number of grain size classification have evolved, but the commonly used ones are:
U.S Bureau of soils and PRA classification
International classification
M.I.T. classification
I.S classification (IS : )

7. Textural classification:
Soil occurring in nature are composed of different percentage of sand, silt and clay. Soil classification of composite soils exclusively based on the particle size distribution is known as textural classification.
The triangular classification system suggested by U.S. Bureau of Public Roads is commonly known as textural classification.
The term texture is used to express the percentage of the three constituents of soil, namely sand, silt and clay.

9. UNIFIED SOIL CLASSIFICATION:
The unified soil Classification system was first developed by casa grained in 1948, was intended for use in airfield construction during world war II.
Coarse grained soils:
If more than 50% of the soil is retained on No.200 (0.075 mm) sieve, it is designated as coarse grained soils.
If the course grained soils contains less than 5 % fines
And are well graded(w), they are given the symbol GW and SW , and if poorly graded (P) , symbols GP and SP.

10. Coarse grained Soils Gravels (G) Sands (S)
50% or more of coarse fraction retained on 4.75 mm sieve
Sands (S)
More than 50% of coarse fraction passing through 4.75 mm sieve

11. 2. Fine grained soils:
Fine grained soils
Silts and clay liquid limit 50% or less symbols ML,CL,OL
Silts and clay liquid limit more than 50% symbols MH,CH,OH

12. Organic soil (O) are included in this group
Organic soil (O) are included in this group. The plasticity chart devised by casagrande and used for the USCS. The A-line in the chart has the equation Ip=0.73(WL -20).
This A-line generally separates the ore clay like materials from silty soils and also the organic soils from inorganic soils.
Slit clay and organic fractions are further subdivided in to soils possessing low (L) or high (H) plasticity when the liquid limit is less than 50% and more than 50%, respectively.

13. (GRAVITATIONAL WATER)
SOIL WATER
SOIL WATER
FREE WATER
(GRAVITATIONAL WATER)
HELD WATER
TYPES OF SOIL WATER:
The water present in the voids of soil mass is called soil water.
The soil water is broadly classification into two main categories as under:
Structural Water
Adsorbed Water
Capillary Water

14. FREE WATER:
‘Free water’ is the water in excess of the moisture that can be retained by the soil. Free water moves in the pores of the soil under the influence of gravity, it is also known as ‘gravitational water’
Free water flows from one point to the other where there is a difference of head . The rate at which the head is lost along the flow passage is equal to the hydraulic gradient.
The flow of free water in soils is just like laminar flow in pipes.
It is capable of transmitting pressure when free water fills completely all voids the soil is said to be saturated.
The upper surface of the zone of full saturation of soil, at which the ground water is subjected to atmospheric pressure is called the ‘Ground water table’ .

15. HELD WATER:
‘Held Water ‘ is that water which is held in the pores of the soil mass because of certain forces of attrition. It is not free to move under the influence of gravity.
Held water is further divided in to three types:
Structural water:
The water chemically combined in the crystal structure of the mineral of soil is called ‘ Structural water’ This water cannot be removed with out breaking the structure of the mineral.
A temperature of more than 300 C is required for removing the structure water. In soil engineering , the structural water is considered as an integral part of the soil solids.

16. 2. Adsorbed water:
Water held by electrochemical forces existing on the soil surface is known as ‘Adsorbed water’.
Properties of adsorbed water are:
It has more viscosity.
Greater surface tension.
It is heavier than normal water.
The boiling point is higher than normal water
The freezing point is lower than the normal water.
It imparts plasticity to soils.

17. 3.Capillary water:
The water held in the interstices of soils due to capillary forces is called ’capillary water ’.
This water is in suspended condition within the interstices and pores of capillary rise of the soil.

18. Capillary water exists in soils so long as there is an air- water interface.
As soon the soil is submerged under water, the interface is destroyed, and the capillary water becomes normal, free water.
The capillary water is always under tension (negative pressure).
However, the properties of capillary water are the same as that of normal, free water.
Surface tension :
Surface tension is defined as the force oer unit length of a line drawn on the surface of water.
It acts in the direction of normal to that line.
The surface tension of water at normal temperature is about N/m at 20C.
It decreases with an increase in temperature.

19. Due to surface tension, he top surface of water acts like a thin film and a small needle can float on water, insects can walk on water surface.
Capillary Rise :
If the lower part of mass of dry soil comes into contact with water, the water rises in the voids to a certain height above the free water surface.
The upward flow into the voids of the soil is attributed to the surface tension of water.
The height to which water rises above the water table against the force of gravity is called a capillary rises.
The height of capillary rise is greatest for very fine grained soil materials.

20. THANK YOU