Which statement about comparing rotosonic and hollow-stem auger drilling is true?

Which statement about comparing rotosonic and hollow-stem auger drilling is true?

• A. Hollow-stem auger is faster for unconsolidated soils but may not recover intact samples; rotosonic provides better core recovery in hard soils
• B. Rotosonic is faster in all soil types and yields better cores
• C. Hollow-stem auger always yields best cores in all soils
• D. There is no difference between the methods

Answer: (A)

The main idea is that drilling methods trade speed for sample quality depending on soil type. Hollow-stem auger often moves fastest in loose, unconsolidated soils because cuttings are easily lifted and transported to the surface, so you can advance quickly. However, in these loose conditions the sample inside a core can be disturbed or lost, leading to poorer intact core recovery. Rotosonic drilling, on the other hand, uses high-frequency vibration to reduce friction and help cut through tougher, more cohesive or dense materials, which tends to preserve and recover a better, longer continuous core in hard soils. Because of that difference, the statement correctly reflects that hollow-stem auger is faster in unconsolidated soils but may not yield intact samples, while rotosonic provides better core recovery in hard soils. The other options overstate one method’s performance across all conditions or deny any difference, which don’t fit how these techniques behave in varying soils.

The main idea is that drilling methods trade speed for sample quality depending on soil type. Hollow-stem auger often moves fastest in loose, unconsolidated soils because cuttings are easily lifted and transported to the surface, so you can advance quickly. However, in these loose conditions the sample inside a core can be disturbed or lost, leading to poorer intact core recovery. Rotosonic drilling, on the other hand, uses high-frequency vibration to reduce friction and help cut through tougher, more cohesive or dense materials, which tends to preserve and recover a better, longer continuous core in hard soils. Because of that difference, the statement correctly reflects that hollow-stem auger is faster in unconsolidated soils but may not yield intact samples, while rotosonic provides better core recovery in hard soils. The other options overstate one method’s performance across all conditions or deny any difference, which don’t fit how these techniques behave in varying soils.