From Civil Engineering Wiki Encyclopedia

Contents 1 Soil 1.1 Definition 1.1.1 Dry soil 1.1.2 Partially saturated soil 1.1.3 Saturated soil 1.2 Formation of Soil 1.3 Composition of soil 1.4 Physical Properties of soil 1.4.1 Soil texture 1.4.2 Soil structure 1.5 Soil color 1.5.1 Bulk density 1.6 Strength of Soil

Soil

Definition

It is an aggregate of particles and voids. It can also be defined as Material which nourishes and supports growing plants; includes rocks, water, snow, air etc. It is a mixture of mineral matter, organic matter, water, and air.

In soil voids there may be air or water or both at the same time, so on the basis of this soil is divided into three classes given below:

Dry soil

If only air is present in the voids, then it is called as the dry soil.

Partially saturated soil

If air along with water is present in the voids then it is called as the partially saturated soil.

Saturated soil

If the voids contain only water then it is called as the saturated soil.

Formation of Soil

Soil is formed by one or combination of the following processes:

• Trans-locations
• Transformations
• Additions
• Losses

Composition of soil

Soil is composed of Mineral matter, Organic matter, Air and Water. The inorganic components of soil are:

• Sand
• Silt
• Clay

The inorganic materials are the rocks that have been broken down into smaller pieces. The size of the pieces varies. It may appear as pebbles, gravel, or as small as particles of sand or clay.

Physical Properties of soil

Soil texture

Soil structure may be

• Granular
• Platy
• Wedge
• Blocky
• Prismatic
• Columnar etc.

Soil structure

Soi Structure means:

• The arrangement into aggregates of desirable shape and size
• The stability of the aggregate
• The configuration of the pores

Soil color

Soil color is :

• The indicator of different soil types
• The indicator of certain physical and chemical characteristics
• Due to humus content and chemical nature of the iron compounds present in the soil

Bulk density

• Bulk density is determined by dividing the weight of oven-dry soil in grams by its volume in cubic centimeters.
• The variation in bulk density is due largely to the difference in total pore space

Strength of Soil

As soils are frictional materials so the strength of soil mainly depends upon the applied stress, type of soil, its composition and the type of drainage condition in the soil. Strength of Soil can be measured by:

• Shear Test
• Triaxial Test