What is the purpose of the Shelby tube in field compaction measurement?

• A. To measure permeability
• B. To extract soil samples
• C. To measure soil density
• D. To measure soil moisture

Answer: (B)

The Shelby tube is primarily designed for extracting undisturbed soil samples from the field, which is essential for various types of soil testing and analysis, including geotechnical investigations. When conducting these investigations, obtaining undisturbed samples is crucial for accurately assessing the in-situ properties of the soil, such as its strength, compressibility, and other characteristics that may be affected by disturbance.

While the Shelby tube can indirectly aid in density and moisture calculations through the analysis of the extracted samples, its main function is to ensure that the integrity of the soil structure is maintained during the sampling process. This is particularly important in cohesive soils where disturbance can significantly alter the soil behavior. In this context, using the Shelby tube is a standard practice in soil investigation, allowing for effective evaluation and application in engineering projects.