Types of soil
Soil is a natural aggregate of mineral particles with or without organic content, which can be separate easily by mechanical means such as, agitation in water, frost, wind etc. Rock, on the other side, is also a material of earth crust which supports a building. It is a hard and compact natural aggregate of mineral particles cementing by strong permanent bonds. Knowledge is very essential for achieving safety and economy in foundation design and construction.
TYPES OF SOIL, ENCOUNTER IN CONSTRUCTION OF A BUILDING
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Gravel ( soil particles varying from 4.75 mm to 80 mm )
The soil particles varying from 4.75 mm to 80 mm are refer as gavel. These are formed due to the disintegration of rocks and are transport by water from their source. Gravel do not exhibit swelling and shrinkage properties on wetting and drying respectively. These provide the best foundation surface, other than rock, for all types of structure. these are cohesion less soil particles.
Sand ( soil particles varying from 0.75 mm to 4.75 mm )
The soil particles varying from 0.75 mm to 4.75 mm are refer as sands. These are the cohesion less particles of silica derive from the disintegration of rocks. These are more permeable but do not allow water to rise up through the capillary action. It provides a good foundation surface provide it is enclose with the help of sheet piles wall etc. Sand is further classified according to particle size as coarse sand ( 2 mm – 4.75 mm ), medium sand ( 0.425 mm – 2 mm ) and fine sand ( 0.075 mm – 0.425 mm )
Silt ( particles varying from 0.002 mm to 0.075 mm )
The soil particles varying from 0.002 mm to 0.075 mm are refer as silt. It is a fine grain soil with little or no plasticity. It is less permeable as compare to sand. The non plastic variety consists of same size particles of quartz and plastic variety consists of appreciable percentage of flaky particles.
Silt exhibits the slight tendency of swelling and shrinkage and therefore, is not regard as good foundation material.
Clay ( particles having sizes less than 0.002 mm )
The soil particles having sizes less than 0.002 mm are refer as clay. These are derive from the chemical decomposition and disintegration of rock constituents. Clay exhibits the plastic property within a moderate range of water content. The permeability is very low and it is also exhibits the properties of swelling, shrinkage and capillary rise of moisture in the soil. The bearing power is very low and hence liable to cause more settlements. It provides cohesion and it cracks on drying because moisture is always present in its pores.
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