What is consolidation? , Primary consolidation, secondary consolidation

 Consolidation:-

The the compression of a saturated soil under static pressure is known as consolidation.
It is occurs due to expulsion of water from the voids.
The the soil particles shift from one position to other by rolling and sliding thus they attain a closer packing.
The decrease in soil volume occurs not due to compression of solids or water but due to shifting of soil particles as water escapes.
Consolidation can occurs due to one or more of the following factors.

1. Due to external static loads from the structure.

2. Due to self weight of soil such as recently placed fills.

3. Due to lowering of the ground water table.

4. Due to desiccation.

Primary consolidation:-

After initial consolidation further reduction in volume occurs due to the expulsion of water from the voids.
When saturated soil is subjected to a load or pressure initially all the pressure is taken up by water as an excess pore water pressure.
As water is almost incompressible as compared with soil solid particles a hydraulic gradient develops and water start flowing out and decrease in volume occurs.
The decrease depends upon the permeability of soil and is therefore time-dependent.
This reduction in volume is called primary consolidation.


Secondary consolidation:-

The reduction in volume continues at a very slow rate even after the excess hydrostatic pressure developed by the applied pressure is fully dissipated primary consolidation is complete.
The additional reduction in volume is called secondary consolidation.
It is attributed to the plastic readjustment of the solids particles and the the adsorbed water to new stress system.
Primary and secondary consolidation


Comments

Post a Comment

Popular posts from this blog

What is castiglious I and II theorem and it's applications 2021

Image
Castiglious I theorem:- If the material is linearly elastic,supports are unyielding and temperature is constant,Then the first partial derivative of total strain energy with respect to the diflection/slope will give the load/moment at that point.      Derivative of total strain energy w.r.t diflection Derivative of total strain energy w.r.t slope Where:- U= strain energy P= load M= moment ∆= diflection   θ    = slope Assumptions:- 1. Material is linearly elastic 2. supports are unyielding   3. temperature is constant  Castiglious II theorem:- The  The first partial derivative of the total strain energy w.r.t. the load/ moment will give the diflection/ slope    first partial derivative of the total strain energy w.r.t. the load/ moment will give the diflection/ slope  Derivative of total strain energy w.r.t load Derivative of total strain energy w.r.t moment
Read more

Kaolinite, illite, montmorilonite, How the clay minerals kaolinite, illite and montmorillonite are formed by schematic diagram.

Image
 Kaolinite:- Kaolinite is the most common minerals of the kaolinite group of clay minerals. Its basic structural unit consists of gibbsite  sheet with aluminium atoms at the center. It is joined to silica sheet through the unbalanced oxygen atoms at the apexes of silica sheet. The total thickness of the basic structural unit is about 7 angstrom. The basic structural unit of kaolinite minerals is symbolised as shown in figure. Kaolinite minerals The basic structural units of kaolinite minerals are joined together by hydrogen bond. It develops between the oxygen atoms of silica sheet and the hydroxyls of gibbsite sheet. Since the hydrogen bond is fairly strong, it is extremely difficult to separate the layers, and hence, kaolinite minerals is relatively stable. Moreover, water cannot penetrate through the layers of the structural units of kaolinite minerals. Kaolinite shows relatively little swell on wetting. China clay is almost pure Kaolinite. Montmorillonite Montmorillonite is the mos
Read more

Bettie's law (Rayleigh theorem),What is Bettie's law? 2021

Image
  Bettie's law (Rayleigh      theorem):- When material is linearly elastic, supports are unyielding and temperature is constant Then the virtual work done by P-system of forces in going through displacement caused by Q-system of forces is equal to the virtual work done by Q-system of forces in going through displacement caused by P-system of forces. Limitations :- 1.material is linearly elastic 2.temperature is constant 3.supports are unyielding Example:- Special cases for Bettie's law:- Case -1 :- If theta-1 be the rotational displacement in the direction of M1 caused by  M2 and theta-2 be the rotational displacement in the direction of M1 caused by M1.
Read more