Soil Structure

 मृदा संरचना

"Soil particles, the arrangement of water and air in the soil body and, in these users, the working classes, say the soil body structure" is of great importance in soil structure. Soil properties such as permeability (permeability), alkali resistance (traction resistance), etc. depend on soil structure."

 You can divide the Soil particles into the following three groups based on the soil particles acting on them at the time of sedimentation .

a. Single grained structure,

b. Honeycomb structure,

c. Flocculent structure,

(These three types of structures can reunite and form new structures.)

 (a). Similar particle structure:-

This is the simplest type of structure. It consists of deposits of approximately spherical particles of similar size, such as table tennis balls filled in boxes. This structure is found in substances in which there is no possibility of particles joining. These types of substances are called cohesionless substances and in the soil are called sand or gravel. At the time of sedimentation, only their own weight is working on them. The strength of these granular soils depends on many things such as how the Soil particles are divided into groups, etc. But not all particles in sand are spherical in the same shape, but their porosity is almost equal to the ideal soil sample. Porosity of such types of soil is found to be between 50% to 20% and blank ratio between 1 to 0.3. Fig. 1. (a)

Fig. 1. (a)-Single grained structure

(b).  Honeycomb structure:-

This structure is found in very fine soils, which are synthesized due to fineness. In this structure, the molecules are located in their fixed positions due to the attraction force among themselves. When two particles come into contact with each other, the molecules of one particle exert an attractive force on the contact point of the other particle. These forces depend on the magnitude of the particles. If the size of the particles is larger then this force will be negligible. For example, the particles of sand are very large due to which the force of attraction acting at the place of contact of their particles is negligible, due to which it is called non-cohesive. The smaller the particle, the greater the force. For example, let A particle become depressed and comes in contact with B particle, which has already been depressed. Now if the mass of A particle is greater than the force of attraction, then the particle will slip on B and the structure shown in Fig. 2. (b) will be formed. If the particle is small enough that the value of the force of attraction is high, then the structure shown in Fig. 1.6 (c) will form and thus a porous structure, as shown in Fig.6 (d). This is only a graphical display. It is not possible to accurately represent the actual structure in the picture. This structure is found in fine silts and clays. The force acting at the place of contact is called fusion.

Fig. 2. (b)-Honeycomb structure

(c). Flocculant structure:-

This structure is found only in soils with very fine particles. The sedimentation speed of particles in water is proportional to the square of their diameter. It is very less in microscopic particles. These particles combine together to form Floc. These floc themselves are cellular structures. Due to the increased size, these molecules depressurize and regrow together to form a honeycomb structure (Figure 1.7). This structure is called flocculent structure. These structures come together to form new structures. They are found in most marine clays. These are very hard in an intact state, but become very soft when they are mixed with water.

Depending on the mobility, the water present in the soil can be divided into the following two parts.

1. Free water - 
This is the water present in the soil which is free to go anywhere and flows through the soil by the effect of gravitational force. It is also called Gravitational water.

2. Held Water-
 This water is present in the soil due to the effect of various forces and cannot flow freely into the voids. This is why it is called Held water.
 They can be divided again into the following parts.

2.1. Structural water - 
It is the water present in the soil which is bound by chemical reactions in the crystal structure of clay minerals. It can be separated only by breaking the crystal structure (eg by heating the soil to a high temperature). The amount of this water is very small and it is no different when the soil is heated to 110 ° C. From an engineer point of view, it is considered as an integral part of soil particles.

2.2. Absorbed water - 
A thin film of water remains as a result of electric forces around the soil particles. This type of water, which remains due to electro-chemical forces near the soil particles, is called Absorbed water. It is also called Hygroscopic water. The physical properties of this water, such as viscosity, surface tension and boiling point, are higher than ordinary water. The water near the particles is almost in solid state. When the soil is heated in the oven, the amount of adsorbed water is reduced but it is not completely eliminated. As soon as the dry soil in the oven is exposed to the humid atmosphere, it again absorbs water from the atmosphere.

2.3. Capillary water - 
Water present in the voids between capillaries due to the capillary force in the voids is called capillary water. Its volume depends on the measurement of runes. The smaller the pandra, the higher it will reach the water in the soil.

Interparticle Force in Soil Mass

soil particles

There are two types of forces acting between soil particles:

(1) Gravitational force,
(2) Surface force.
 Soils with coarse particles have a higher gravitational force value. Its value is proportional to the weight of the soil code. In such soils, the surface area of   soil particles is very less. Therefore, the surface forces are negligible, but in microfiber soils, the surface area of   particles is much higher than their weight, that is, the value of surface forces is higher.
 While the value of gravity forces, negligible surface forces can be divided into the following two parts-
 (i) Attractive force,
 (ii) Repulsive force.
There are many types of attraction forces. Due to the attraction forces, particles of microcircular soils come into contact and form a structure by joining together.