PHYSICAL PROPERTIES OF SOILS
Soils are viewed by Agriculturists and Engineers are in different way. The soil which is suitable may not suitable for civil Engineer for construction. Agriculturists look the soil in growing plant life, where as Civil Engineer study the soil behaviour and its application for foundations.
1.Plasticity: It is the ability of the soil to undergo deformation without cracking. Soil contain clay and it is in wet, it can be moulded into various shapes in plastic stage. If the soil contain non plastic material like quartz, rock floor, it would not become plastic.bntl 3.2mm (18)inch
2. Cohesion: The sollcapacity to resist shear stresses is known as cohesion. When the water percentage of very fine grained saturated by consolidation the volume of voids occupied by water decreases. However volume occupied by the absorbed substances remains same.
3. Consolidation: Consolidation is defined as the gradual process of reduction in volume under sustained static loading.Consolidation is the process of reduction of volume of saturated soil due to removing out water from the soil
4. Compaction: Compaction is the artificial process of packing the soil particles together by mechanical means to reduce the void ratio of the soil and increase dry density of soil. Soil need to be compacted such as in laying of highways, formation of railway lines, formation of earth bunds etc. For cohesive soils need to be compacted by rollers and cohesionless soils by vibration.
Objects of Compaction:
1. To decrease the permeability and water absorption of soil
2. To reduce the settlement of soil under loading.
3. To increase dry density of soil leads to increase shear strength.
5. Permeability: It is defined as the property of the soil which allows flow of water through it. Soil is porous material with number of interstices and they are inter connected. Permeability varies with size, cross section and orientation of interstices for different soils
6. Compressibility: When a compressive load is applied on soil mass by moving or vibratory loads or expulsion of air from voids leads to decrease in volume under stress is known as compressibility When the voids soil mass is filled with air, compression soil occurs rapidly because of air is compressible and when volds are filled with incompressible water decrease in volume takes place when water expelled out of voids.
ENGINEERING PROPERTIES OF SOILS
1.Porosity : the ratio of volume of total voids to total volume. us ACK Porosity: it is It is denoted by the letter ‘n’ and it is expressed as percent
n = Vv/V * 100
2.Voids Ratio: It is the ratio of total volume of voids to volume of soil solids. It is denoted by the letter ‘e’ and is expressed as decimal
e = Vv/Vs
3. Water Content: The ratio of weighte of water W_{w} the weight of solids Ws in the voids, is called water content, It is denoted by ‘W’ and it is expressed as percent
W = Ww/Ws * 100
4.Specific Gravity: It is defined as the ratio of weight of a given volume of soil solids to the weight of an equal volume of water at that temperature or It is defined as the ratio of density of solids (r{1}) de density of water (rw)
Gs = rs/rw
5.Density: It is defined as the ratio of its weight to its volume. It is denoted by the letter γ
γ = W/V
TYPES OF SOILS
Soils are formed by weathering rocks due to disintegration and chemical decomposition.
The soils are classified into two types according to formation.
1. Residual soils
2. Transported soils se nove. Howto
1. Residual Soils: When the soil available at its formation just above the parent rock, it is known as residual soil. These soils are available at shallow depth and engineering properties vary from top layer to bottom layer. Bottom layer of soil resembles that of parent rock in many aspects.
2. Transported Soils: When the soil available at a place away from the place of its origin, it is called Transported soil. These soils are available at considerable depth. The different ways of transporting and redepositing soils are water, wind, ice and gravity.
(a) Water Transported Soils: The soils are transported through water flow is called water transported soils. When the velocity gets reduced coarse particles are gets deposited.
(b) Transported Soils by Wind: The soils are also transported by winds. A dust storm gives an evidence of the soil particles carried by this method.
(c) Glacier Deposited Soils: The glaciers move the soils from the formation place and carry soils varying size from fine grained to huge boulders. The deposits made by glaciers are called drift, deposits made by melting of glaciers are called ’till’
(d) Gravity Deposited Soils: Soils transported by gravity force is called talus and it consists of irregular coarse particles.
