Question

Which of the following orientation of beds is most suitable for dam construction?

• A. beds which are faulted
• B. beds which are folded
• C. beds with gently inclined in upstream direction
• D. beds with steep upstream dip

Hint:

Upstream-dipping beds help resist seepage; gentle dip ensures safety and stability.

Answer 1

The Correct Option is C

To determine the most suitable bed orientation for dam construction, we analyze geological stability factors for dam foundations.

1. Understanding Dam Foundation Requirements:
The ideal geological conditions should prevent water leakage and ensure structural stability under the dam's weight and water pressure.

2. Evaluating Each Option:
- Faulted beds: Highly undesirable due to potential leakage and weakness zones
- Folded beds: Creates complex stress patterns and potential leakage paths
- Gently inclined upstream: Correct answer - provides optimal conditions
- Steep upstream dip: Risk of sliding and instability

3. Why Gently Upstream-Inclined Beds Are Best:
- Creates natural "shingles" that resist water pressure
- Allows water to press beds tighter together (more water-tight)
- Provides better load distribution for dam weight
- Reduces risk of downstream sliding
- Typical recommended dip: 10°-30° upstream

4. Problems with Other Orientations:
- Faulted/folded rocks have discontinuities that may leak
- Steep dips may lead to bedding plane slippage
- Horizontal beds offer no advantage against seepage
- Downstream dips are worst-case scenario (promote leakage)

5. Engineering Considerations:
When gently upstream-dipping beds are present: - Grout curtains are more effective
- Foundation treatment costs are reduced
- Long-term monitoring shows less seepage
- Dam safety is enhanced

Conclusion:
The most suitable bed orientation for dam construction is beds with gently inclined in upstream direction.

Final Answer:
The correct option is: beds with gently inclined in upstream direction.