Soil

 

Soil - According to the general definition, soil is a heterogeneous, pigmented substance in which particles of soft and hard clay, loam, silt and gravel etc. According to civil engineers, soil is that hard layer of mineral and organic particles in various types of small stones etc. Different types of soils have different amounts of different components which are shown in Table 6.1. The main source of soil is rocks. Rock - It is a naturally hard and dense group of mineral particles in which different particles are firmly bound to each other. There are generally three types of rocks.

1. Igneous rock It is formed by the cooling of molten material of lava. Good examples are granite, basalt, etc.

2. Sedimentary rock – It is formed by the solidification of sediment carried by water. Sandstone is an example of that.

3. Metamorphic rock Rocks formed by the effect of pressure and temperature on igneous or sedimentary rocks are called metamorphic rocks like slate.

Soil formation The geological cycle continues on the surface of the earth, due to which soil compaction takes place. The following activities usually take place in the geological cycle.

1. Weathering

2. Transportation

3. deposition

4. Upheaval

(1) Weathering - The weathering of natural rocks occurs by atmospheric effect, due to which the rocks are divided into small pieces. • Weathering effects can be divided into two main categories.< /span>

(i) Physical Components - Physical weathering of rocks occurs due to temperature change, flow of water on rocks, friction and impact of ice and air.

(a) Effect of heat- As we know that rock is made up of various mineral and organic elements whose expansion coefficients are different, due to change of temperature, the expansion of different particles of the rock or

Contractions are also different, due to which different particles of rock are separated or separated from each other. Apart from this, due to the generation of tensile and compressive forces due to temperature change in rocks, cracks develop in them. When water gets filled in these cracks, it turns into ice, due to which its volume increases and the internal stress increases in different components of the rock.

Which breaks the rock into pieces. This process is also called ice funnel or wedge process.

(ii) Roots of tres growing on the surface of rocks also act like snow and help in dissolution of rocks.

(iii) Weathering of rocks also occurs due to the impact and friction caused by flowing water, moving wind, and sliding of ice. Chemical components present in the atmosphere, gas, acid vapor and other components are helpful in weathering rocks. The following processes usually take place between rock particles and atmospheric components.

(a) Oxidation

 (b) Hydration

(c) Carbonation 

(d) Water Analysis

(a) Weathering by Oxidation

 In this process, oxygen (ions) react with the mineral particles of rocks and di singer ate them. The weathering of rocks that contain ferrous minerals is due to oxidation.

(b) Hydration 

 In this process the structure water of the rock reacts with the mineral elements of the rock and weather it. Soil with fine particles are formed by the process of hydration.

(c) Carbonization

Acid is formed! The chemical reaction of the dust and organic acids of the mineral elements of the rock is called carbonization. Limestone is particularly affected by this action. Generally, organic acids also affect rocks containing mineral like iron, calcium, magnesium, sodium, potassium etc.

Water analysis - 

in this process the ions of the mineral substances of the rock 164

When replaced by hydrogen ions, a new more stable substance is formed. On the basis of geological, soils can be classified as follows.

Residual soil - The soils which remain on the same rocks from which they are formed are called residue soils. The thickness of the residual soil layer is relatively small.

Transported soil - The soils which are removed from their parent rocks by water or wind and deposited at some other place are called transported soils. The thickness of this type of soil layer is relatively high.

Colloid: A colloid is a particle whose relative surface is so large that its properties are governed by its surface energy rather than its mass energy. That is, it is a very fine particle. Its maximum size is 2x 103 mm.

Transport and Deposit The following means of soil transport and deposition

(agencies) are: (1) water,

(2) snow,

(3) Air,

(4) gravity

Of these, water and air are the main means of soil transport and deposition. The effect of wind occurs in the following three ways:

(a) It removes loose particles of rocks from there. From

(b) With the help of these particles, they cause weathering of other rocks by means of abrasion.

 (c) To deposit these particles at some other place.

Fine particles of soil are removed from one place by wind and deposited on another. Soil formed in this way is called sand dune or dune. Some scientists say that the soil of Rajasthan is formed by the wind. Many such sand dunes are found here.

Soil formed by water is called alluvial soil. of India

The silt brought by the plain water between the Ganges and the Yamuna rivers

formed due to the accumulation of This soil is usually very fertile. Soil formed by snow is called glacial soil. Upheaval - Due to the geological cycle, there is an uplift in the earth. It has been seen that where there were earlier seas, now there have become mountains and where there were earlier mountains, now there have become seas. After the completion of one cycle, the dissolution of the high places starts again and this process continues.

Classification of Soils- Soils formed by transport and deposition can be classified into following classes: (i) Alluvial soils – This soil is mixed with water.It is formed due to the deposition of flowing silt.

(ii) Aeolian Soil – This type of soil is made by transporting it by air. Like sand dunes. (iii) Lacustrine soil at the bottom of lakes

Soil formed is called lake soil. (iv) Marine soil: The soil formed at the bottom of the sea is called marine soil.

(v) Glacial soil The soil formed by transporting snow is called glacial soil.

Colluvial soil The soil formed by the accumulation of small pieces of rocks at the bottom of the mountains due to the force of gravity is called ocean.

Glacial Drift The soil formed by the melt water of the ice lifting the material from the rocks and carrying it along with it and depositing it at another place is called glacial.

In addition to the above classification, soil can also be classified as follows:

(1) Coarse grained soil (2) Fine grained soil

(3) Organic soil

(1) Coarse granular soil is also called granular or granular or non-cohesive soil. The size of their particles is so large that they can be seen with the eye. Gravel and sand fall in this category.

(2) Soils with fine particles are also called non-cohesive soils. Their particles cannot be seen with the naked eye. Silt clay or clay comes in this category.

(3) Organic soil- This soil is the result of rotting and decomposition of vegetation. Peat muck etc. come in this category. 

type of transport

Soil Classification

Water

1. Alluvial Soil

2. Marine Soil 3. Lake Soil

Wind

1. Acolian 2. Sand dunes

gravity

Sea Soil (Colluvial) Rear-ft (glacial)

ice

Soil Mechanics - This is the branch of physics that describes the properties, type and performance or function of soil as a material of foundation and construction works. It also gives an idea of ​​the application of the laws of solid and liquid mechanics on the soil. Soil Engineering - It is an applied science that deals with applying the laws of soil mechanics to solve practical problems.

Properties of soil Due to being a natural soil incompatible material, its properties are also different. Soil properties can generally be divided into the following two categories.

(1) Engineering properties In this category, the important properties of soil are permeability, compressibility, shear strength, etc. Huh.

(2) Index properties Those properties of soil which are indicative of soil engineering properties are called soil indicators. Soil indicator properties depend on the size of the soil particles. Soils can be classified into the following two groups according to the size of the particles.

(a) coarse-grained soil

(b) Soils with fine particles The main indicator properties of fine-grained soils are At Berg boundaries and soil compaction, while the main indicators of coarse-grained soils are particle size and their relative density. Mechanical Analysis The analysis of the size of particles is called mechanical analysis. This analysis can be done in two ways.

(a) Sieve analysis - This method is adopted for particles larger than 75 microns. In this method the soil is filtered through a set of sieves. Sieves of sieve size 80mm, 40mm, 20mm, 10mm and 4.75m are used. 2mm, 1mm, 600 mm, 425 mm, 212 mm, 150 mm, and 75 mm sieves are used for sieve analysis of soils with particles smaller than 4.75 mm.

is done.

(b) Sedimentation analysis – This method is used for particles smaller than 75 microns. This analysis is based on Stock's law and can be done with the help of a hydrometer and pipette. Particle Size Distribution Curves: These curves show the distribution of particles of different sizes in the soil mass. These are also called soil grading curves. These curves are drawn on semi logarithmic graph paper. Advantages of Semi-Small Counter Diagram- It has the following advantages.

1. The shape of the curves of the particles of the soils of uniformity is approximately

is identical. The actual size of the particles has no effect on the shape of the curves.

2. Due to the large difference in the size of the particles, logarithm • paper is used.