Skip to main content

Boring type for road sub-grade

Short answer

Auger boring is best because road sub-grade investigation is shallow (1–3 m). It is cheap, fast, and light, allowing many closely spaced holes along the alignment. It provides disturbed but representative samples sufficient for classification, moisture content, Atterberg limits, compaction, and CBR tests.

What type of boring is best suited for sub-grade investigation of roads and why?

Auger boring (hand auger or small power auger) is the best method for road sub-grade investigation.

  • Sub-grade soil is needed only to a shallow depth (about 1-3 m below formation level), where augers work well.
  • It is cheap, fast and light, so many holes at close spacing (about 250-500 m or less) can be made along the alignment.
  • It gives disturbed but representative samples that are enough for classification, moisture content, Atterberg limits, compaction (OMC, MDD) and CBR tests.
  • It needs little equipment and is easily taken to hilly road sites. Test pits can be used additionally for in-situ density and CBR checks.

✓ Answer checked by Claude Sonnet 5.5

Related questions

All Foundation Engineering chapter 2 questions →