- 2080 Chaitra · 2 marks
Short note: Weathering
Short answer
Weathering is the in-situ breakdown of rocks by physical, chemical, and biological processes. It reduces rock strength, increases porosity, and causes landslides. Weathering grades are used in rock classification for foundations and slopes.
Write a short note on weathering.
Weathering is the in-situ breakdown and decay of rocks at or near the earth's surface by the action of atmosphere, water and organisms, without transport of the material.
Types
- Physical (mechanical): frost wedging, temperature changes, salt crystal growth, unloading (exfoliation) and root action break the rock into pieces without changing its composition.
- Chemical: oxidation, hydrolysis, carbonation and solution change minerals (feldspar to clay, calcite dissolves).
- Biological: roots, burrowing animals, lichens and bacteria.
Factors
Climate (rain, temperature), rock type and mineral stability, joints, topography and time. Warm, humid climate gives deep chemical weathering.
Engineering significance
- Lowers strength, increases porosity and permeability of foundation rock.
- Weathered rock needs deeper excavation and flatter slopes.
- Causes landslides and rock falls on cut slopes.
- Weathering grades (fresh, slightly, moderately, highly, completely weathered) are used in rock classification.
- Weathered material forms residual soil and clay, which may swell.
✓ Answer checked by Claude Opus 5.5 (high effort)