NBR 6459 - Solo - Determinação do Limite de Liquidez

Summary

This video tutorial explains the procedure for determining the liquidity limit of soil according to the Brazilian standard NBR 6459. It covers the preparation of soil samples, the use of the Casagrande apparatus, and the importance of minimizing moisture loss during testing. Key steps include homogenizing the soil, creating a groove, and measuring the number of blows required for closure. Results are analyzed through moisture content and blow count, with the liquidity limit defined at 25 blows. The video serves as a comprehensive guide for engineers and students interested in soil testing methodologies.

Takeaways

• 😀 The NBR 6459 standard outlines the procedure for determining the liquidity limit of soil.
• 🌡️ The test should be conducted in climate-controlled environments to minimize moisture loss.
• 💧 Start with 100 grams of prepared soil sample placed in a porcelain capsule.
• 🔄 Water should be added gradually while mixing to achieve a homogeneous paste.
• 🔨 A consistent mixture should require approximately 35 blows to close the groove.
• ⏳ Homogenization time varies; 15 to 30 minutes is recommended, especially for clay soils.
• ⚖️ Transfer soil to the Casagrande apparatus and ensure no air bubbles are present.
• ✋ A groove is created using a chiseling tool; count the blows until the groove edges unite.
• 📊 Collect data on moisture content and number of blows to generate results.
• 📈 The final liquidity limit is determined by plotting moisture content against the number of blows.

Q & A

What is the purpose of NBR 6459?

NBR 6459 provides guidelines for determining the liquidity limit of soil, which is crucial for evaluating its behavior and suitability in construction and engineering projects.

What are the initial steps for preparing the soil sample according to NBR 6459?

The soil sample should be prepared following the NBR 6457 standard, and equipment like the Casagrande apparatus must be calibrated and checked for integrity before starting the test.

Why is it important to conduct the test in a controlled environment?

Testing in a controlled environment minimizes moisture loss due to evaporation, ensuring accurate results in determining the soil's liquidity limit.

How much soil is needed for the test?

A sample size of 100 grams of soil is used for the test.

What is the desired consistency of the soil paste during the preparation?

The soil paste should be homogeneous and have a consistency that requires about 35 blows to close the groove created during the test.

How is the groove formed in the soil sample?

A cinzel is used to create a groove in the center of the soil sample, and the sample is gently struck against a solid surface to help open the groove.

What should be done if the groove cannot be closed after more than 25 blows?

If the groove cannot be closed with more than 25 blows, the sample is considered to have no liquidity limit.

What procedure follows the completion of the test?

After testing, the soil samples are dried in an oven at 105-110°C and then stored at room temperature for further mass determinations.

How is the liquidity limit determined from the test results?

The liquidity limit is determined by plotting the moisture content against the number of blows on a logarithmic scale and identifying the moisture content corresponding to 25 blows.

What should be done with the results after plotting the graph?

The liquidity limit should be reported based on the results from the graph, ensuring that the value is rounded to the nearest integer.