Statement (I): The critical condition of d/s slope occurs when the reservoir is full and percolation is at its maximum rate. Statement (II): The direction of seepage forces tends to increase the stability.
- ABoth Statement (I) and Statement (II) are individually true and Statement (II) is the correct explanation of Statement (I)
- BBoth Statement (I) and Statement (II) are individually true but Statement (II) is not the correct explanation of Statement (I)
- CStatement (I) is true but Statement (II) is falseCorrect
- DStatement (I) is false but Statement (II) is true
Solution
Concept
Seepage and slope stability of earth dams
Step-by-step solution
1. The downstream slope is most critical at full reservoir with steady seepage (Statement I true). 2. Seepage forces act outward and downward along the slope, so they reduce the stability (Statement II false).
Explanation
The seepage forces add to the driving forces on the downstream slope and reduce the effective stress, which lowers its factor of safety.
Why the other options are wrong
Options with II true are wrong because seepage reduces stability.
Shortcut
Seepage ↓ stability of the downstream slope.
Common mistake
Thinking seepage helps stability.
Correct answer: C) Statement (I) is true but Statement (II) is false