- 2078 Bhadra · 2 marks
Free earth versus fixed earth support
Short answer
Free earth support uses shallow embedment with freely rotating tip, larger bending moment, no contraflexure, and simple statics. Fixed earth support requires deeper embedment to fix the tip, introduces reverse curvature with a contraflexure point, smaller bending moment, and more complex analysis like equivalent beam method.
Write down the differences between free earth and fixed earth support anchored pile.
| Point | Free earth support | Fixed earth support |
|---|---|---|
| Embedment depth | Shallow (smaller) | Deeper (larger) |
| Toe condition | Pile tip is free to rotate; no fixity | Pile tip is fixed against rotation (zero slope at the tip) |
| Passive pressure | Only in front of the pile; the pile acts as a simply supported beam between the anchor and the soil reaction | Passive pressure in front, and a counter (reverse) passive force behind the toe |
| Bending moment | Larger maximum moment | Smaller maximum moment (with a negative moment near the toe) |
| Deflected shape | One curve, no contraflexure | Has a point of contraflexure |
| Analysis | Simple statics, moments about the anchor | Equivalent beam (Blum) or other methods; more complex |
✓ Answer checked by Claude Sonnet 5.5
Related questions
- Anchored sheet pile, free earth procedure · Foundation Engineering, chapter 5
- Anchored sheet pile, free earth, with anchor pull · Foundation Engineering, chapter 5
- Fixed beam: end moments from support rotation or settlement · Theory of Structures II, chapter 3 · asked 4×
- ILD: moment at support B, fixed-propped beam · Theory of Structures II, chapter 4
- ILD: vertical reaction at fixed support · Theory of Structures II, chapter 4
- ILD: bending moment at fixed support, 10 m beam · Theory of Structures II, chapter 4