GATE CE 2018 Set 2 — Question 28

MCQ+1 / -0.33EasyCalifornia Bearing Ratio TestAggregate TestsTransportation Engineering

Transportation Engineering → Aggregate Tests → California Bearing Ratio Test

Last updated 5 September 2026

Question

The initial concavity in the load-penetration curve of a CBR test is NOT due to

Correct answer (B) high impact at start of loading Solution In a California Bearing Ratio (CBR) test, the load-penetration curve sometimes shows an initial concavity. This is usually due to surface irregularities or improper seating of the plunger. Common causes include: Uneven top surface: The plunger doesn't make full contact immediately. Inclined penetration plunger: The plunger is not perfectly vertical, leading to non-uniform initial contact. Soft top layer: A very soft or loose layer at the top of the specimen (often due to soaking) provides little resistance initially. High impact at the start of loading is a procedural error but does not typically cause the characteristic initial concavity that requires a zero-point correction in the standard test analysis. Turn this into a strength. Explore AI-powered practice and doubt support with Success Tracker.

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Correct answer (B) high impact at start of loading Solution In a California Bearing Ratio (CBR) test, the load-penetration curve sometimes shows an initial concavity. This is usually due to surface irregularities or improper seating of the plunger. Common causes include: Uneven top surface: The plunger doesn't make full contact immediately. Inclined penetration plunger: The plunger is not perfectly vertical, leading to non-uniform initial contact. Soft top layer: A very soft or loose layer at the top of the specimen (often due to soaking) provides little resistance initially. High impact at the start of loading is a procedural error but does not typically cause the characteristic initial concavity that requires a zero-point correction in the standard test analysis.

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