Which sampling device is best suited for collecting undisturbed soil samples?

The most suitable sampling device for collecting undisturbed soil samples is the Shelby tube. This device is specifically designed to obtain core samples of soil without disturbing the structure of the sample. The Shelby tube has a thin-walled, cylindrical design that helps minimize disturbance to the soil when it is inserted into the ground and extracted.

When sampling soil, it is crucial to maintain the natural structure and moisture content of the sample, which the Shelby tube accomplishes effectively. The integrity of the soil layers is preserved, allowing for a more accurate analysis of the soil's properties, such as density and compaction, which is essential for various environmental assessments and engineering applications.

Other options like the auger and split spoon are less effective in collecting undisturbed samples because they generally disturb the soil structure during the process. The Veihmeyer rod, while useful for certain soil properties, does not provide a solid core sample and is more suited for measuring soil moisture. Therefore, for accurate and undisturbed soil sampling, the Shelby tube is the preferred choice.