[Mekanika Tanah 1]: Standard Penetration Test SPT

Summary

In this instructional video on Soil Mechanics, the focus is on the Standard Penetration Test (SPT). The SPT is a method used to determine the dynamic resistance of soil and take disturbed soil samples during drilling. Key equipment includes a drilling machine, pump, and a 63.5 kg hammer. The test involves measuring the number of blows required to penetrate the soil every 15 cm, with specific steps for accurate data collection. The SPT's advantages include soil type identification and sample collection, while the main drawback is the discontinuity in soil profiling. The test is stopped when the number of blows exceeds 50, indicating dense soil.

Takeaways

• 😀 The Standard Penetration Test (SPT) is used to assess soil properties by drilling and determining both the dynamic resistance and disturbed soil samples.
• 😀 SPT is conducted using specific equipment, including a drilling machine, hammer, and other tools, with a focus on the correct height and weight of the hammer for accurate testing.
• 😀 The SPT test consists of drilling to a desired depth, followed by hammer blows, with the first 15 cm of penetration not counted to eliminate the effect of drilling.
• 😀 The SPT measures how many hammer blows are required to penetrate 15 cm intervals in the soil, starting with the second 15 cm as the counting phase.
• 😀 The SPT test is stopped when the number of hammer blows exceeds 50 or if the total depth reaches a minimum of 6 meters.
• 😀 A correct SPT procedure includes cleaning the hole before testing and ensuring that the hammer falls vertically from a height of 75-76 cm.
• 😀 The N1 value from SPT represents the number of blows required for the first 15 cm, which is considered the drilling portion and is not counted in the results.
• 😀 The N2 value represents the number of blows required to penetrate the second 15 cm, and N3 refers to the third 15 cm, which is then added together to get the total resistance value.
• 😀 SPT results can help identify soil types visually and determine soil density, while its main limitation is that the soil profile is not continuous between tests.
• 😀 The SPT test is crucial for determining soil characteristics, including density and hardness, which are essential for various engineering projects, such as foundation design.

Q & A

What is the Standard Penetration Test (SPT)?

The Standard Penetration Test (SPT) is a field test used to determine the dynamic resistance of soil and to obtain disturbed soil samples. It is conducted simultaneously with drilling using a hammer to drive a sampling tool into the soil.

What equipment is used in the SPT test?

The SPT test requires a drilling machine, a pump machine, a sample structure, a hot roll retaining hammer, and other supporting equipment such as tal wrenches.

How is the SPT test performed?

In the SPT, a hammer weighing 63.5 kg is dropped from a height of 75-76 cm onto a tool inserted into the drilled hole. The number of blows it takes for the tool to penetrate 15 cm is recorded, with the first 15 cm considered as drilling and not counted.

When do we stop the SPT test?

The SPT test is stopped either when the number of blows exceeds 50 or when the depth reaches a minimum of 6 meters, indicating that a hard or dense soil layer has been reached.

What is the purpose of counting the number of blows in the SPT?

The number of blows is counted to measure the soil's resistance to penetration. The number of blows needed for the tool to penetrate 15 cm helps determine the soil's density and strength.

Why are the first 15 cm not counted in the SPT?

The first 15 cm are not counted because they are considered part of the drilling process, not a true representation of the soil's resistance.

What is the significance of the 'N1', 'N2', and 'N3' values in the SPT?

'N1' refers to the number of blows needed for the first 15 cm, which is not counted. 'N2' and 'N3' are the blow counts for subsequent 15 cm intervals, and their sum (N2 + N3) is used to assess the soil's density.

What are the advantages of the SPT?

One of the main advantages of the SPT is that it allows for both the determination of soil resistance and the collection of soil samples, which can be used for further testing.

What are the disadvantages of the SPT?

The main disadvantage of the SPT is that the soil profile is not continuous. The test involves taking discrete samples at intervals, so it may not provide a continuous profile of the soil's conditions.

How is the accuracy of the SPT test ensured?

The accuracy of the SPT test depends on correctly measuring the height from which the hammer falls (76 cm) and ensuring that the hammer is dropped vertically. Any deviation from these requirements can affect the results.