Disturbed And Undisturbed Soil Sample | Disturbed VS Undisturbed Soil Sample | Importance Of Soil Samples

The collection of different types of the soil samples is done during the sub-surface exploration which is done by different methods of Boring such as-

1. Auger Boring
2. Wash Boring
3. Rotary Drilling
4. Percussion Drilling

When we hear the word “soil sampling” in civil engineering then a question arises What is soil sampling? The soil sample is basically an amount of soil that is collected for the study of different properties of the soil to get a better understanding of the site where we are going to start our construction project.

Let’s talk about the different types of soil samples:

Types Of Soil Sample

Basically, in civil engineering, there are two main types of soil sample that is collected for the study of the properties of soils:

1. Disturbed Soil Samples
2. Undisturbed Soil Samples

Disturbed Soil Samples

During the sampling process of the soil sample If the natural structure of the soil gets disturbed, then this type of soil sample is called a Disturbed Soil Sample.

The Disturbed Soil Samples can be used for the determination of the grain size, plasticity characteristics, and specific gravity of the soil.

Here is a question that arises How do we collect the disturbed soil samples? The collection of disturbed soil samples is done by different methods such as Auger Boring, Wash Boring, Rotary Drilling, and Percussion Drilling, even if the disturbed soil sample is collected by hand excavating of soil with picks and shovels.

Undisturbed Soil Samples

During the sampling process of the soil sample, if the natural structure of the soil and water content does not disturb, that means the soil retained its natural structure and water content, then these types of soil samples are called undisturbed soil samples.

But we have to remember that it is impossible to get a truly undisturbed soil sample. The top and bottom of the soil sample were disturbed during the collecting time of soil samples. During the test time, the engineers ignore the disturbing portion of the samples.

The undisturbed soil samples are used for the determination of engineering properties of soils such as shear strength, permeability, and compressibility.

The undisturbed soil samples are collected by Thin-walled samplers.

 Design Factors Affecting Sample Disturbance

The disturbance of soil depends mainly depends upon the following design features:

1. Area Ratio
2. Inside Clearance
3. Outside Clearance
4. Inside Wall Friction
5. Design Of Non-Return Valve
6. Method Of Applying Force

Area Ratio– For obtaining a good quality of undisturbed soil sample, the area ratio should be 10% or less.

The area ratio is calculated by the formula that is given in the below image.

Inside Clearance– For an undisturbed sample the inside clearance should be between 0.5 to 3%.

The inside clearance is calculated by the formula that is given in the below image.

Outside Clearance- For an undisturbed soil sample the outside clearance should be lies between 0 and 2%.

The outside clearance is calculated by the formula that is given in the below image.

Inside Wall Friction– The inside surface of the sampler should be smooth, so the disturbance due to friction is less.

Design Of Non-Return Valve– The non-return valve should be of proper design so it allows water, air, slurry to escape quickly when the different types of the sampler are driven.

Method Of Applying Force– Soil sample how much going to disturb mainly depends on In which manner we apply the forces.

Difference Between Disturbed And Undisturbed Soil Samples

Here are the following difference between disturbed and undisturbed soil samples:

Disturbed Soil Samples	Undisturbed Soil Samples
The disturbed soil samples are basically those soil samples whose natural structure gets disturbed during the sampling process of soil.	The undisturbed soil samples are basically those soil samples that retain their natural structure and water content during the sampling process of soil.
The disturbed soil sample is required for tests like to determination of specific gravity, grain size, plasticity, etc.	The undisturbed soil sample is required for tests like to determination of compressibility, permeability, etc.
It is obtained by auger boring, wash boring, rotary boring, etc.	It is obtained by Thin-walled samplers.

Importance Of Soil Sampling In Civil Engineering

The question is Why soil sampling is so important from a civil engineering point of view? So from the civil engineering point of view, soil sampling is the most important step because before starting the construction process as a civil engineer we have to know the different properties of the soil like what is the bearing capacity of the soil, the grain size of soil, the permeability, compressibility, specific gravity, etc.

The soil sample test gives exact information like how much building load the soil is going to sustain, and what type of foundation we should provide so the differential settlement would be minimum, and we got a lot of information that helps us to construct a better project having a long life.

Civil engineering projects like the construction of highways, railways, canals, bridges, etc required soil tests before the starting of these projects.

Frequently Asked Questions (FAQ)