Formation of Soil

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As we know we have many type of soil around us. Soil may be classified in many type. But, today we will see formation of soil.

Soils are formed by weathering of rocks and decomposition of organic matter. So soils are organic or inorganic depends upon source of origin.

The weathering of soil occurs with time will decrease cohesive property of soil within the grain and this results in disintegration of the big rock masses into small particles. We called this small particles as soil. Hence the soil formation is the result of weathering action.

Types of Weathering:

Generally, the soils are formed either by,

     (1)   Mechanical weathering

     (2)   Chemical weathering

(1) Mechanical weathering:

Mechanical weathering occur due to physical disintegration of the parent rock. Physical disintegration can occur due to following reasons:

Temperature changes: 

All types of rocks may not have same thermal coefficient. So they behave differently for the different temperatures values. This will cause the thermal expansion and contraction with change of the temperature. If this process repeated several times, its results in disintegration of and soil are formed.

Wedging action of ice:

All rocks are have some pores that gets filled up with water. During low temperature, this water freeze and convert into ice and little increase in volume occur. This volume change will make area expand in rock pores. This result into cracks and further expansion will propagate the cracks. This will lead to break the rock and convert as soil.

Spreading of roots of plants: 

Sometime there are trees and shrubs grown near the rocks. The roots of these trees and shrubs grow inside the rocks and formed cracks in rock mass. The segment of the rock are forced apart and this action disintegrate the rock and further it will results in formation of soil.

Abrasion: 

Movement of wind, water and glaciers over the rock surface will result in abrasion and scouring. It result in soil formation.

All this physical disintegration of parent rock won’t bring any change in chemical composition of rock. The property of soil will be similar to that of parent rock. The soil formed by physical weathering are sand, gravel and some other coarse-grained soils.

(2)  Chemical Weathering:

Transformation of hard rock into soft and erodible material is conducted through process of chemical weathering. Let’s see some process of chemical weathering:

Hydration: 

In this process, water combines with the rock minerals and results in the change in chemical composition. The chemical reaction causes a change in volume and decomposition of rock. As example of hydrolysis of SiO₂.

Carbonation: 

In carbonation, carbon dioxide in the atmosphere combines with water to form carbonic acid. This carbonic acid reacts chemically with rock and causes their decomposition. Sedimentary rocks which contains calcium carbonates are the formed by chemical reaction of rocks by carbonation.

Oxidation: 

Oxidation occur due to oxygen ions combine with rock minerals. Oxidation results in decomposition of parent rock.

Solution: 

Some rock minerals make solution with water when they get dissolved in water. Some chemical reaction takes places in this solution and because of this soil are formed.

Hydrolysis: 

Hydrolysis is chemical process in which water gets dissociated into H⁺ and OH^-- ions. Hydrogen cation replace some metallic ions such as sodium, calcium and potassium present in the rock minerals and this will result into soil formation.

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Types of Columns in building Construction

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Types of Columns in Building Construction:

Columns are classified based on some conditions which include:

1.     Based on Types of Reinforcement

2.     Based on Types of Loading

3.     Based on Slenderness Ratio

4.     Based on Shape

5.     Based on Construction Material

Based on Types of Reinforcement 

1. Tied Column

This column is usually construction from reinforced concrete. Longitudinal reinforcement is confined closely within spaced tie reinforcement. It is estimated that 95% of all columns used in buildings construction are tied.

2. Spiral Column

This column is also construction from reinforced concrete. In spiral column, longitudinal reinforcement bars are confined within closely spaced and continuously wound spiral reinforcement.

Some lateral restrains (Poisson's effect) and delays axial load failure is provided by Spiral reinforcement.

3. Composite column

In composite column longitudinal reinforcement is in the form of structural steel section or pipe with or without any longitudinal bars.

This type of column consists high strength with small cross section, in addition to exhibit good fire performance too.

Based on Types of Loading

1. Axially Loaded Column

In this column vertical axial loads act on the CG (center of gravity) of the cross-section of the column.

This column is rare in construction since coinciding vertical loads on the center of gravity of column cross section is not practically possible in all structure.

This column is used as interior column in multi-storey buildings with symmetrical load from floor slabs to all sides.

2. Column with Uni-axial Eccentric Loading

In this column vertical loads do not coincide with center of gravity of column cross section, but rather act eccentrically either on X or Y axis of the column cross section.

This column generally come across in the case of columns rigidly connected beam from one side only such as edge columns.

3. Column with Biaxial Eccentric Loading

In this column vertical load on the column is not coincide with center of gravity of column cross section and does not act on either axis (X and Y axis).

This column is common in corner columns with beams rigidly connected at right angles at the top of columns.

Based on Slenderness Ratio

Based on slenderness ratio, (effective length/ least lateral dimension), columns are categorized as follow:

1. Short Column

In this column ratio of effective length of the column and the least lateral dimension is <12. This column is generally fails by crushing (compression failure).

2. Long Column

In this column ratio of effective length of the column and the least lateral dimension exceeds 12. Generally, this column fails by bending or buckling.

Based on Shape

Shape of Reinforced Concrete Column

1. Square or Rectangular Column

This column is used in most of building construction. The construction of this column is easy and casting is also easy compare to other shape because of shuttering and to support it from collapsing due to pressure while the concrete is still in form in flow.

2. Circular column

This column is specially design column. This column is used mostly in piling work.

3. L-Shape Column

Commonly, L-shaped column is and has similar characteristics of a rectangular or square column.This type of column is commonly utilized in the corners of the boundary wall. The characteristics of this column is similar to rectangular or square column.

4. T-Shape column

This column utilized based on design requirements of a structure. In bridge construction this type of column is mostly used.

5.Shape of Steel Column

There are different standard and built up shape of steel columns which you can see below Fig.

   Fig.: Steel column cross section shape (Standard)

                                            Fig.: Steel column cross section shape (built up)

6. Shape of some Composite Column

Some shape of composite columns is shown in Fig.

Based on Construction Material

Types of columns based on construction materials include.

I think no description is needed to understand this type of columns.

1. Reinforced Concrete, Steel, timber, Brick, Block, and Stone Column.

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Types of Beams in Construction

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A beam is a structural element that primarily resists loads applied laterally to the beam's axis. Its mode of deflection is primarily by bending. The loads applied to the beam result in reaction forces at the beam's support points. The total effect of all the forces acting on the beam is to produce shear forces and bending moments within the beam, that in turn induce internal stresses, strains and deflections of the beam.

Now we discuss about classification of beam used in building construction.

Classification of beams based on supports:

1.    Simply supported Beam:

This is type of beam which is supported on the ends which are free to rotate and have no moment resistance.

2.    Fixed Beam:

This is type of beam which is supported on both ends and restrained from rotation.

3.    Over hanging:

In this type of beam a simple beam extending beyond its support on one end.

4.    Double overhanging beam:

Its another type of overhanging beam, but in this beam a simple beam with both ends extending beyond its supports on both ends.

 

5.    Continuous beam:

Continuous beam is a beam in which a beam is extending over more than two supports.

6.    Cantilever beam:

Cantilever beam is a rigid beam that is fixed to a support usually a vertical structure or wall and the beam's other end is free.

Classification of beams based on Geometry

1.      Straight beam:

This beam has straight profile.

2.      Curved beam:

As name suggest this beam has curved profile.

3.      Tapered beam:

The cross section of this beam is tapered

4.      Based on the shape of cross section:

This type of beams is no need to explanation.

I.       I-beam:

II.      T-beam:

III.     C-beam:

Classification of beams based on materials:

This type of beam has also no need to explanation

1.    Timber Beam

2.    Steel Beam

3.    Concrete beam

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