Question

For full reservoir condition in a gravity dam, the critical combination of vertical and horizontal earthquake accelerations to be considered for checking the stability is ________________________

(a) vertically upward and horizontally downstream

(b) vertically downward and horizontally downstream

(c) vertically upward and horizontally upstream

(d) vertically downward and horizontally upstream

The question was asked in an online quiz.

The question is from Design of Gravity Dams in chapter Gravity Dam Design and Construction of Irrigation Engineering

Answer 1

Correct option is (b) vertically downward and horizontally downstream

For explanation: Horizontal inertia force should be considered to be acting at the center of the gravity of the mass regardless of the shape of cross-section and it acts horizontally downstream in worst cases under full reservoir case. This force would produce the worst results is it is additive to the hydrostatic water pressure (acting towards the downstream).