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Reginald Morrison
Facilities manager
Asked a question last year

Why is the degree of saturation of soil treated as constant throughout the consolidation process?

As the consolidation process continues, water will be expelled out. Why is the degree of saturation of soil treated as constant throughout the consolidation process?

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The degree of saturation is the ratio of the volume of water to the volume of voids. Consolidation happens when the soil is in a fully saturated condition. That is, after all, air from voids got expelled by compaction of soil it will be fully saturated and then the consolidation starts. Thus as the volume of water reduces by consolidation, the volume of voids also reduces at the same rate. So there will be a constant degree of saturation. Finally, almost all water gets expelled out and the volume of voids will become negligible and then the plastic rearrangement of soil particles (secondary consolidation) will take place.

Seth Morgan
Construction Superintendent

Degree of consolidation of saturated soil:

Well, consolidation is simply a process of settlement of soils due to reducing in the volume of soil and it is occurs due to the expulsion of water from the vaults of a given soil mass.

Whenever all the voids in the soil sample are filled with water then that type of saturation is 100% Consolidation occurs when a reduction in the volume of a soil which equals to the volume of water expelled out Whenever does given salt sample is not 100% saturated then above criteria will not be satisfied and hence such type of phenomenon is called as compression.

Therefore consolidation can occur only hundred percent saturation condition

I hope so my answer is helpful to you.

Thank you.  

Peter Smith
Heating and ventilation engineer

Consolidation is the process of settlement of soils due to reduce in the volume of soils, which occurs to the expulsion of water form the voids of soil mass.

Consolidation theory is applicable only for saturated clayey soils. The soil has to necessarily be saturated during the test. If the soil is completely saturated, the degree of saturation is 100%. So , during the process of consolidation, the degree of saturation always remains 100%

What is consolidation? Consolidation is the process of settlement of soils due to reduce in the volume of soils, which occurs to to expulsion of water form the voids of soil mass.

What is 100% percent saturation? All the voids in the soil mass is filled with water. No pore is left unfilled.

Now, you think of a situation where the soil mass of 1 m3 has (0.6 m3 of solids, 0.3 m3 of water and 0.1 m3 of air-filled). In this case saturation is not 100%, which is 80% percent here. In this case when the load is applied on the soil, soil will settle down due the reduction in the air filled voids. Which is called compression not consolidation.

So, if consolidation has to occur, reduce in volume of soil must be equal to the volume of water expelled out. If soil is not saturated 100%, above criteria will not be satisfied, hence such phenomenon will be called as compression.

So, consolidation can occur only in 100% saturation condition

  • Consolidation theory is applicable only for saturated clayey soils.
  • The soil has to necessarily be saturated during the test.
  • If the soil is fully saturated, the degree of saturation is 100%. So, while the process of consolidation, the degree of saturation always remains 100%.

The degree of saturation denotes the actual relationship between the weight of moisture existing in a space and the weight that would exist if the space were saturated.

It can be also said as the percentage of water that occupies the pore spaces present in soil and is said to be degree of saturation. Basically, the soil has three phases soil solid, water and air. If the pore and void space in the soil is fully occupied by water, then it is fully saturated and the degree of saturation is 100%. If the void space in the soil is partially occupied by water, then it is said to be partially saturated.

Lillian Holmes
Director of Public Works

Hi,

  1. Consolidation itself means that reduction in the volume of soil if it is fully saturated.
  2. Otherwise, it is called compaction If saturation is not equalled to a hundred per cent.
  3. In the consolidation process, we need to decrease the volume but not decrease the amount of water in it. This process is called a consolidated undrained process. In this way, the degree of saturation must be maintained up to 100% to get the final result of consolidation test.
  4. Whereas in the consolidated drained test, water allows to remove from the wall pore, and there is no need to maintain the degree of saturation up to 100%.

Hope you the concept.