Question

The vertical downward earthquake acceleration av = 0.1g acting on a gravity dam will ________________________

(a) increase the resisting weight of the dam by 10%

(b) decrease the resisting weight of the dam by 10%

(c) increase the uplift by 10%

(d) decrease the uplift by 10%

I got this question in an online interview.

My question is taken from Gravity Dam Design topic in section Gravity Dam Design and Construction of Irrigation Engineering

Answer 1

Correct option is (b) decrease the resisting weight of the dam by 10%

To elaborate: The net effective weight of the dam is given as W [1 – Kv] and vertical acceleration av = Kv.g = 0.1.g i.e 10%

where W is the total weight of the dam and Kv is the fraction of gravity adopted for vertical acceleration.

This is considered as the worst case for design as the foundation tries to move downward away from the dam body when there is downward vertical acceleration. This reduces the effective weight and the stability of the dam.