How to Determine the Specific Gravity of Soil in Lab | Using Pycnometer Method | Geotech with Naqeeb

Summary

In this video, the process of performing a specific gravity test on soil is demonstrated, including an overview of the necessary apparatus such as volumetric flasks, balance scales, and heating equipment. The steps involve weighing soil samples, preparing a slurry with water, and boiling the samples to remove air bubbles. After allowing the samples to cool, the final weight measurements are recorded, and specific gravity is calculated using a formula. The video follows ASTM guidelines for conducting the test on silty clay, providing clear instructions on how to achieve accurate results for determining soil's specific gravity.

Takeaways

• 😀 The specific gravity test of soil is performed to determine the density of the soil sample.
• 😀 The necessary apparatus for the test includes a volumetric flask, funnel, soil sample, balance, hot plate, and more.
• 😀 The soil sample used must be oven-dried and pass through a sieve with a number 4 mesh.
• 😀 For silty clay soil, the recommended amount of soil for the test is 35 ± 5 grams.
• 😀 The initial step involves weighing the volumetric flask to record its mass.
• 😀 The soil sample is then placed into the volumetric flask using a funnel.
• 😀 Two trials are performed, and the average specific gravity value is taken for accuracy.
• 😀 Distilled water is added to the flask up to the 1/3 or 1/2 depth of the flask's main body, according to ASTM standards.
• 😀 The flask is agitated to create a slurry, and the entrapped air is removed either by heating or using a Bunsen burner.
• 😀 The heating method involves boiling the soil slurry while continuously agitating it until air bubbles are removed.
• 😀 After the heating process, the flask is cooled to room temperature before filling the flask with water to the 250 ml mark for measurement.
• 😀 The final weight of the flask, water, and soil is recorded to calculate the specific gravity of the soil using a formula.
• 😀 The specific gravity of the soil calculated from the given test procedure is 2.61.

Q & A

What is the purpose of the specific gravity test of soil?

The specific gravity test of soil is used to determine the density of the soil particles, which helps in understanding its characteristics and behavior in construction projects.

What equipment is needed to perform the specific gravity test of soil?

The equipment required includes a 250 ml volumetric flask, a funnel, wash bottles, an oven-dried soil sample (passing sieve #4), a water-filled cylinder, a china dish, a scoop, a cleaning cloth, balances, and a hot plate.

How do you prepare the soil sample for the test?

The soil sample should be oven-dried and must pass through sieve #4. The weight of the sample is usually 35 ± 5 grams for silt or clay soils, based on ASTM standards.

Why is the mass of the flask important during the test?

The mass of the flask is crucial as it ensures that the weight of the flask plus the dry soil is accurately recorded. This helps prevent any errors in calculation during the test.

What is the purpose of agitating the flask during the test?

Agitating the flask ensures that the soil and water mix thoroughly, forming a slurry. This helps in eliminating air bubbles and ensures uniform distribution of the soil particles.

What method is used to remove air bubbles from the slurry?

Air bubbles are removed by using the hot plate method. The flask is heated while continuously agitating the mixture, which helps in eliminating the entrapped air bubbles.

Why is it necessary to boil the soil sample during the test?

Boiling the soil sample helps to break down any air bubbles trapped within the slurry. This ensures a more accurate measurement of the soil's specific gravity.

What is the role of the 250 ml volumetric flask in this test?

The 250 ml volumetric flask is used to hold the soil slurry and water mixture. The volume of water is adjusted to fill the flask between one-third and one-half of its total depth initially, and then up to the 250 ml mark after boiling and cooling.

How do you calculate the specific gravity of the soil?

The specific gravity of the soil is calculated using the formula that involves the weight of the flask plus soil, the weight of the flask with water, and the weight of the water alone. This calculation is performed after the slurry is prepared and the flask is filled to the 250 ml mark.

What is the significance of using 35 ± 5 grams of soil for this test?

Using 35 ± 5 grams of oven-dried soil ensures consistency in the test. The amount of soil needed varies depending on the type of soil, but this range is standard for silt or clay, as per ASTM guidelines.