- Asked 3/26
- 2079 Chaitra · 2 marks
Surface versus sub-surface investigation
Short answer
Surface investigation studies ground exposures (mapping, air photos) to identify rock type, structure, and landslids; it is quick and cheap but limited to exposed features. Sub-surface investigation (test pits, boring, driling) provides depth, stratigraphy, and engineering properties directly, but is costly and point-wise.
Differentiate between surface and sub-surface site investigation methods.
| Point | Surface investigation | Sub-surface investigation |
|---|---|---|
| Meaning | Study of surface exposures and ground features | Study of ground below the surface |
| Methods | Geological mapping, air-photo, remote sensing, outcrop study | Test pits, trenches, boring, drilling, adits; geophysics |
| Stage | Reconnaissance and preliminary | Preliminary to detailed |
| Information | Rock type, structure, landslides, geomorphology | Depth, thickness of strata, bed rock, water table, properties |
| Cost and time | Low, quick | High, slow |
| Accuracy | Limited, only exposed ground | Better for depth |
| Samples | Few | Disturbed and undisturbed samples |
✓ Answer checked by Claude Opus 5.5 (high effort)
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