Types of Soil & Suitable Soil for Foundations Bed

Type of Soil (Civil-Ideas.com)

In this article you will learn about different types of Soil and Suitable soil for any structure’s foundation bed.


Soil is sediments or other unconsolidated accumulations of solid particles produced by the chemical and physical disintegration of rocks which may or may not contain organic matter.

Types of Soil

The soil on which the foundations of various types of structure is to be constructed are classified into:

(1) Sand

The grain size of Sand varies between 0.075mm to 2mm. The shape of the grains may be angular, rounded or irregular and silica is the major constituents of sand.

Image result for sand for construction

Properties of Sand

  • It doesn’t shrink when dry.
  • It doesn’t swell when wet.
  • It is cohesionless.
  • It doesn’t affected by the action of frost.
  • It doesn’t allow water to rise up by capillary action.


Coarse sand provides a good foundation bed. Since it is angular shape that’s why it prevent the structures from slipping and also from escaping from under surface of the foundation concrete. Fine and saturated sand are not suitable for foundation use.

(2) Gravel and Shingle

This type of soil consists of mostly big size particles of coarse material resulting from the disintegration of rocks and often transported by water from their original source. Size of the particles varies from 3 mm to 200 mm. The stone particles having size more than 200 mm are termed as boulders.

Image result for gravel and shingle in construction

Properties of Gravel and Shingle

  • It is not affected by freezing of water.
  • It doesn’t swell when wet.
  • It doesn’t shrink when dry.
  • It has great power and strength of load bearing.
  • It doesn’t settle over the load.


Gravel and Shingle provides a good foundation bed and is suitable for foundation of almost all types of structures.

(3) Clay

It consists of particles having grain less than 0.002. It is composed of microscopic and sub-microscopic particles of weathered rocks. It consists of particle having grain size less than 0.002 mm.

Wet Clay

Properties of Clay

  • Clay can retain it shape vertically when hard but flows down when wet and exert pressures.
  • It consolidates under load and may cause settlement of the structure.
  • It is cohesive type of soil.
  • It shrinks and cracks when dry.
  • It swells and heaves when wet.


It is suitable for foundation of ordinary and light structures. But when heavy structure is to be constructed then must check through various laboratory tests because it is can settle down when saturated. It is also difficult to excavate when dry or when heavily saturated.

(4) Silt

It is finer variety of soil having grain size of 0.002 mm to 0.6 mm.

Silty Soil

Properties of Silt

  • It has slight tendency towards swelling and shrinkage.
  • It is relatively impervious.
  • It is not as superior is sand.
  • It is generally found in beds of river, canals and reservoirs.


It is not considered as a good foundation material.

(5) Alluvial Soil

This soil is transported by water forces and mixed with soils of different origin. When velocity of water reduced then large size particles are start settling down. On further reduction of the velocity of water, still smaller fraction separates out. Thus the alluvial soils are deposited according to the grains sizes.

Alluvial Soil Deposit

Properties of Alluvial Soil

  • It is a cohesive soil.
  • It is plastic but consolidate under load.
  • It Cracks on Drying.


This type of soil are suitable for light Structures.

(6) Black Cotton Soil

This type of soil is inorganic in nature. It is also called peat and bungum.

Black Cotton Soil

Properties of Black Cotton Soil

  • It swell when confined between walls.
  • It can withstand a high pressure in dry state.
  • It becomes so soft during rains that even mam cannot walk through it.
  • It is dark, grey or black in color.


It is the most unreliable soil for foundation bed.

(7) Reclaimed soil

This is also known as made-up soil. This types of soil consist of ballast or brick bats, ashes, old iron pieces etc used for filling the low lying areas or back filling

Properties of Reclaimed Soil

  • Its bearing strength is very low.
  • It is usually porous in nature.


This type of soil is not suitable for laying or constructing structure over it.

Author: Engineer-Nisar

Civil Engineer

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