Gravity Dams

In high dams, the safety against sliding should be checked only for friction.

• True

• False

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

• vertically upward and horizontally downstream

• vertically downward and horizontally downstream

• vertically upward and horizontally upstream

• vertically downward and horizontally upstream

The base width of a solid gravity dam is 35 m and the specific gravity of dam material is 2.45. What is the approximate allowable height of the dam having an elementary profile without considering the uplift?

• 64.68 m

• 54.80 m

• 164 m

• 80 m

A low gravity dam of elementary profile made up of concrete of relative density 2.57 and safe allowable stress of foundation material 4.2 MPa. What is the maximum height of the dam without considering the uplift force?

• 120 m

• 217 m

• 279 m

• 325 m

The vertical stress at the toe was found to be 3.44 MPa at the base of the gravity dam section. If the downstream face of the dam has a slope of 0.617 horizontal: 1 vertical, the maximum principal stress at the toe of the dam when there is no tailwater is

• 1.7 MPa

• 2.4 MPa

• 3.6 MPa

• 4.8 MPa

What is the recommended value of shear friction factor against sliding?

• More than unity

• Less than unity

• More than 3 to 5

• Less than 3

A concrete gravity dam having a maximum reservoir level at 200 m and the RL of the bottom of the dam 100 m. The maximum allowable compressive stress in concrete is 3000 KN/m² and the specific gravity of concrete is 2.4. Calculate the height of the dam and check whether it is a high dam or low dam.

• H = 90 m High gravity dam

• H = 90 m Low gravity dam

• H = 214.2 m High gravity dam

• H = 214.2 m Low gravity dam

The axis of a gravity dam is the ______________

• line of the crown of the dam on the downstream side

• line of the crown of the dam on the upstream side

• centre-line of the top width of the damq

• line joining mid-points of the base

Presence of tail-water in a gravity dam __________

• increases the principal stress and decreases the shear stress

• increases both the principal stress and the shear stress

• decreases the principal stress and increases the shear stress

• decreases both the principal stress and the shear stress

The horizontal component of an earthquake wave producing instability in a dam is the one which acts __________________

• towards the reservoir

• towards the dam

• away from the reservoir

• away from the dam