Soil is defined as an unconsolidated material composed of solid particles produced by disintegration of rocks and decomposition of organic matter. The void spaces between the particles may contain air water or both. Origin of soil is a long process involving mainly physical but sometimes also chemical actions.
So soil is nothing but the disintegrated product of a big rock big rock, rocks will disintegrate or becomes finer particles because of various reasons. Soil origin is from the rocks and their disintegration.
And the soil mechanics is a branch of mechanics which deals with the action of forces on soil and with the flow of water in soil the term soil mechanics was coined by late Dr. Karl Terzaghi who is recognized as the father of soil mechanics. Soil origin or origin of soil is discussed in this soil mechanics topic.
Origin of soil
The soils are originate from the process of disintegration of rocks. Rocks disintegrate by various physical or chemical processes, hence there are two types of weathering of rocks. Types of weathering:-
Physical weathering:- It is due to the physical effects like temperature impression wedging action of the eyes penetration of plant roots etcetera.
Physical weathering results in no change in chemical composition of particles it produces coarse grained and non cohesive soils.
Examples:- Gravel, Sand etc.
Chemical weathering:- It is due to chemical action like oxidation, hydration, carbonation, solution, leaching, hydrolysis etc., organic rock minerals are transformed into clay minerals.
Chemical weathering results in fine grained and cohesive soils mainly like clayey soil. These soils have good capillary action.
Examples:- Clay soils
Classification of soil based on origin of soil:-
Sedimentary soils:- These soil particles credited at one location, transported and finally deposited in another location.
Residual soils:- These are the soils which remain on the parent rock without getting transported like black cotton soil and laterite soil etc.,
Gravitational and surfaces forces:- The gravitational force in a soil particle is proportional to it mass. Therefore the larger the particle size the greater would be the gravitational force.
The gravitational forces are predominant in the case of coarse grained soils namely gravel and sand.
Bonding or surface forces between the particles depend upon the surface area of the particles. As the particle size decreases the surface forces increases and hence the surface forces chemical forces electrical forces are predominant in clay soils.
In the case of silts, both the gravitational and surface forces are important.
Sources and the associated names of soil based on origin of soil:-
|Sl. no||Source of transportation/ deposition||Types of soil|
|4.||Wind||Aeolian soils, ex:- SAND DUNES, LOESS|
|5.||Gravitation||Colluvial soil ex:- Talus|
|6.||Glacier||Glacier deposited soils. Ex:- Drift, till, outwash.|