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Different Soil Tests in Construction

Soil tests are an important part of construction. You may be surprised to know that soil is one of the most important things in any construction project. This is because the type, quality, and structure of the soil directly affect the future stability and performance of a building.

Soil tests involve analyzing samples from the ground to determine their strength, moisture content, pH value, and other factors that may influence construction activities. Construction projects that involve excavating dirt — such as building foundations or digging tunnels — increase the risk of encountering challenging soil conditions.

The first step in determining if there are any issues with your soil is coming up with a plan for testing it. Different projects require different kinds of tests for soil to ensure success before breaking ground. Here are some common types of tests available:

Types of Soil Tests

  1. Moisture Content test on Soil
  2. Atterberg Limits Test
  3. Proctor Compaction Test
  4. Consolidation Test
  5. Permeability Test
  6. Specific Gravity Test
  7. Dry Density Test
  8. Gradation of Soil
  9. Standard Penetration Test (SPT)
  10. Cone Penetration Test (CPT)
  11. Macintosh
  12. Plate Bearing Test
  13. pH value
  14. Triaxial Test
  15. Proctor’s Compaction Test
  16. California Bearing Test (CBR)

Let’s discuss each type of soil test in detail.

Gradation of Soil

Out Come: Particle Size Distribution

The soil gradation test is a more common type of test, and it is also called the sieve analysis test. When it is required to have a certain soil sample with a certain consistency, we check the gradation. With this test we can obtain the particle size distribution of the soil sample.

The consistency of the soil is determined by certain ratios developed based on particle size. Further, the gradation will be used to assess the actual materials used for the construction. For example, in the construction of the dam clay core, we specify the range of gradation (two gradation curves). The actual sample used for the construction shall lie in between the two gradation curves specified.

By this method, we make sure the soil has met the specified criteria.

Moisture Content Soil Tests

You may want to test the moisture content of your soil if you’re concerned that there may be a high-water table nearby, or if you’re working in a coastal area that is regularly affected by flooding.

If you’re planning a project in a flood-prone area, you may want to test the moisture content of the soil before beginning construction.

This will allow you to adjust your design to compensate for the possibility of flooding. If you’re working in an area where water tables are very high, it’s best to test the soil’s moisture content to ensure that it isn’t too wet.

The moisture content of soil can be defined as the mass of water in a soil sample expressed as a percentage of dry mass.

Moisture Content = [ Mass of water in the soil sample / Dry mass of soil] x100%

Testing can be done as per the ASTM D-2216-90 or AASHTO T 265. Depending on the specification we follow the relevant testing standard that could be selected.

There are different methods for evaluating the moisture content of the soil.

  1. Oven drying method
  2. Torsion balance method
  3. Sand bath method
  4. Alcohol method
  5. Radiation method
  6. Calcium carbide method

Atterberg Limits Test

This test is helpful if you are planning to build on or near clay soil. If your soil is clay, it will have a high-water content and be very sticky. Clay is an ideal material for building foundations, but it can become extremely hard when it’s dry.

Testing the soil to determine its Atterberg Limits can help you determine exactly how sticky it is and what adjustments need to be made to your project.

The Atterberg limits are used to classify the soils. Further, they are used to distinguish clay and silt.


It has three limits

  1. Plastic Limit (PL): Soil changing its state from semi-solid to solid
  2. Shrinkage Limit (L): Soil changes its state from plastic to semi-solid.
  3. Liquid Limit (LL): Soil changes from liquid to plastic

Plastic Limit Test

The following apparatus is required for the test.

  1. Glass plate
  2. Drying oven
  3. Pill knife having blade of about 20mm width and 100-130mm long
  4. Metallic road having a diameter of 3.2mm and 100mm long
  5. Containers
  6. Weighing machine having an accuracy of 0.01g

The following procedure could be followed in testing.

  1. Preparation of soil Sample: Take about 20g of a soil sample from the soil to be tested. Mix with water to a level that it can be rolled easily without sticky nature.
  2. Let the sample dry properly and take a specimen weighing of about 1.5-2g.
  3. The soil was sampled and then molded to an ellipsoidal mass. This can be done by hand or by rolling a device. Let’s see the procedure for doing it by hand.
  4. Rolling will be done until the soil mass has a uniform diameter through its length
  5. Thread shall be further deformed on each stroke. So that diameter reaches 3.2mm and takes no more than 2 minutes.
  6. Normally 80-90 stores per minute is recommended. The count a stroke is one complete motion of the hand forward and back to the starting position. The rate of rolling shall be declined for very fragile soils.
  7. When the diameter of the thread becomes 3.2 mm, break the thread into several pieces. Squeeze the pieces together, knead between the thumb and first finger of each hand, reform them into an ellipsoidal mass, and re-roll. Continue this alternate rolling to a thread 3.2 mm in diameter, gathering together, kneading, and re-rolling, until the thread crumbles under the pressure required for rolling and the soil can no longer be rolled into a 3.2-mm diameter thread.
  8. Gather the portions of the crumbled thread together and place them in a container of known mass. Immediately cover the container.
  9. Select another 1.5 to 2.0-g portion of soil from the plastic limit specimen and repeat steps 1 and 2 until the container has at least 6 g of soil.
  10. Repeat steps 1 to 5 to make another container that contains at least 6 g of soil.
  11. Determine the water content of the soil contained in the containers by Test Method D 2216.
  12. Calculate the average of the two water contents (trial plastic limits) and round to the nearest whole number; this value is the plastic limit, PL.

Shrinkage Limit Test

Shrinkage Limit is performed by molding a soil pat of moist test material into a special shrinkage dish. The dish and soil are oven-dried and weighed, then the volume of the specimen is determined by water displacement.

This portion of the Atterberg test series is performed less often and is described in ASTM D4943.

Liquid Limit Test

Liquid Limit machines use a manually cranked cam or a small motor to lift a brass cup to a prescribed height and allow it to drop onto a hard rubber base. A portion of the soil sample is spread in the brass cup and divided using a grooving tool.

The moisture content when the groove closes for 1/2in after 25 drops of the cup is defined as the Liquid Limit. Testing can be done as specified in ASTM D4318.

Proctor Compaction Soil Tests

An experimental approach for establishing the ideal moisture level at which a specific soil type will become most dense and reach its maximum dry density is the Proctor compaction test.

The test is named in honor of Ralph Roscoe Proctor [de], who demonstrated in 1933 that the amount of water present in the soil at the time of soil compaction affects the dry density of soil for a given compactive effort.

Proctor compaction test

The modified Proctor compaction test was later developed from his initial test, which is more frequently known as the standard Proctor compaction test. These soil tests are more frequently done in road construction projects.

  1. Obtain 3 kilograms or so of soil.
  2. Use the No. 4 sieve to filter the soil.
  3. Weight the mold without the collar and the soil mass (Wm)
  4. Add water gradually to the soil in the mixer to get the correct moisture level (w).
  5. lubricate the collar
  6. Depending on the technique used, remove the soil from the mixer and add it to the mold in 3 or 5 layers (Standard Proctor or Modified Proctor). Start the compaction procedure for each layer with 25 blows. The drips are applied steadily either manually or automatically. A maximum of one centimeter of soil mass should fill the mold and extend into the collar.
  7. Trim the soil that extends above the mold using a sharpened straight edge after carefully removing the collar
  8. Weigh the soil that contains the mold (W)
  9. Using a metallic extruder, push the soil out of the mold while keeping the extruder and mold parallel
  10. Measure the amount of water in the sample’s top, middle, and bottom.
    Place the soil again in the mixer and add water to achieve higher water content, (w).

The dry density(Υd) of soil can be calculated as

Υd = [ W – Wm] / [ 1 + w] v


W – the weight of the mold and the soil mass in kg

Wm – the weight of the mold in kg

w – the water content of soil (%)

v – volume of the mold in m3

Consolidation Test

When stress is applied, the volume of partially or completely saturated soil reduces. This process is known as soil consolidation. A load added to a low permeability soil is initially borne by the water already present in the porous, saturated soil, which causes a sharp rise in pore water pressure.

As water drains from the soil’s voids, the extra pore water pressure is released, and it is then transferred to the soil skeleton, where it gradually compresses and causes settlements. The process of consolidation continues until the extra pore water pressure has subsided.

The amount and pace of both primary and secondary consolidation settlement of a structure or an earth fill are estimated using the consolidation parameters discovered during the consolidation test.

These kinds of estimations are crucial for the design of engineered structures and the performance assessment of those structures.

The purpose of the test is to find the consolidation parameter of the soil that can be used to calculate the consolidation settlement.

Permeability Soil Test

The permeability of the soil can be determined using a variety of in-lab and on-site experiments, each of which has benefits and drawbacks. The “constant head permeability method” and “falling head permeability method” are the two most used.

The purpose of a permeability test is to ascertain a sample’s coefficient of permeability (K), which is defined as the rate at which water moves through a porous medium area with a unit cross-section under laminar flow circumstances.

The coefficient of permeability can, however, fluctuate even by a tiny order of magnitude, making it difficult to determine.

Specific Gravity Soil Tests

A crucial characteristic of soils and other building materials is specific gravity. Calculations of soil density, void ratio, saturation, and other soil parameters are done using this dimensionless unit, which represents the ratio of material density to water density.

Applications include calculating the stability of soil embankments, designing the foundations for buildings, and determining the settling of engineered soil fills.

The mass of a unit volume of soil solids at a particular temperature divided by the mass of a unit volume of gas-free, distilled water at that same temperature is known as a material’s specific gravity (Gs). Typically, the specific gravity of soil is stated at 20 °C.

Specific Gravity (Gs) = [weight of a considered volume of soil] / [ weight of the same volume of water]

Generally, specific gravity is calculated at a certain temperature.

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