Tilt test for residual friction

Summary

In this video, the presenter conducts an experiment using a tilt table to explore how the roughness of joint surfaces affects residual friction in rock. Three samples are tested: a smooth cut surface exhibiting a residual friction angle of 22 degrees, a natural joint with 28 degrees, and another natural joint reaching 47 degrees. The experiment highlights the significance of surface roughness on frictional behavior, offering insights into rock mechanics and jointed surfaces in the field. By comparing the profiles of these joints, viewers gain a deeper understanding of the factors influencing rock stability.

Takeaways

• 🔬 The experiment uses a tilt table to study the effects of joint surface roughness on residual friction.
• 🪨 Three different samples are tested, showcasing a variety of joint surfaces.
• 📏 The first sample has a smooth, cut surface and shows a residual friction angle of approximately 22 degrees.
• ⚖️ The second sample, which is larger and natural, displays a rougher texture with a residual friction angle of around 28 degrees.
• 🔍 The third sample, another natural joint surface, reveals a significantly higher residual friction angle of approximately 47 degrees.
• 💡 The roughness of a surface is critical in determining its frictional properties.
• 📊 Residual friction angles increase with surface roughness, demonstrating that smoother surfaces yield lower friction.
• 🔄 The experiments highlight the importance of understanding joint surfaces for predicting rock behavior in geological settings.
• 🔗 The findings have implications for fields such as geology, civil engineering, and natural resource management.
• 🌍 By analyzing these samples, researchers can gain better insights into how rocks behave in their natural environment.

Q & A

What is the purpose of using the tilt table in the experiment?

The tilt table is used to understand how the residual friction of a joint is affected by the roughness of that joint, which helps in understanding rock behavior in field conditions.

How many samples were tested during the experiment?

Three different samples were tested in the experiment.

What characterizes the first sample tested?

The first sample is a cut surface with a smooth finish, which allows for a clear measurement of its friction angle.

What was the residual friction angle measured for the first sample?

The residual friction angle for the first sample was approximately 22 degrees.

How does the weight of a sample affect its friction?

The friction on a surface is more dependent on the coefficient of friction than on the weight of the sample.

What type of surface was the second sample and what was its friction angle?

The second sample was a natural joint with a rougher surface, yielding a residual friction angle of approximately 28 degrees.

What unique feature does the third sample possess?

The third sample is another natural joint surface, characterized by being rougher than the first two samples.

What was the measured friction angle for the third sample?

The third sample had a residual friction angle of approximately 47 degrees.

Why is the comparison of the three samples important?

Comparing the three samples provides insight into how surface roughness affects frictional resistance, which is critical for understanding rock stability.

What conclusion can be drawn about smooth versus rough surfaces based on the experiment?

Smoother surfaces tend to have lower residual friction angles, while rougher surfaces exhibit higher frictional resistance, which has implications for geological assessments.