The factor of safety against overturning of a gravity dam is checked by ensuring that:
Choose the correct answer
The resultant of all forces passes through the centre of the base
The resultant of all forces falls within the middle third of the base (eccentricity e <= B/6)
The dam height does not exceed 100 m
Uplift is completely neglected
Correct Answer
B. The resultant of all forces falls within the middle third of the base (eccentricity e <= B/6)
Why is this the answer?
For gravity dam stability: (1) No tension: resultant within middle third (e <= B/6) for tension-free base; (2) No overturning: sum of resisting moments > sum of overturning moments; (3) No sliding: sum of horizontal forces / sum of vertical forces < permissible friction coefficient.
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