Irrigation (61-80)

61. Horizontal acceleration due to earthquake results in

hydrodynamic pressure ,inertia force into the body of the dam

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62. Hydrodynamic pressure due to earthquake acts at a height of

4H/3π above the base

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63. The major resisting force in a gravity dam is self-weight of dam

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64. Total force due to wave action on a gravity dam acts at a height of

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65. When the reservoir is full, the maximum compressive force in a gravity dam is

produced at the toe

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66. The maximum permissible eccentricity for no tension at the base of a gravity dam is B/6

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67. Presence of tail water in a gravity dam

decreases the principal stress,decreases the shear stress

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68.Neglecting the effect due to earthquake forces and tail water pressure, the

principal stress in a gravity dam is given by

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69.The elementary profile of a dam is a right angled triangle

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70.In the empty condition of reservoir and with the elementary profile of a dam, the vertical stress at heel and toe respectively / are given by 2W/B and 0

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71.Neglecting uplift pressure, the base width of an elementary profile of a gravity dam shall be taken as

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72.The maximum possible height of a safe dam having an elementary profile is

f/W(G+1)

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73. The focus of base parabola for a dam having a horizontal drainage filter is at a

distance of b from toe

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74. By providing a top width for roadway and freeboard in the elementary profile of a gravity dam, the resultant force for full reservoir condition will

shift towards the heel

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75. For wave action in dams, the maximum height of freeboard is generally taken to be equal to

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76. As compared to gravity dams, earthen dams require less skilled labour

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77. The most suitable materiarfor the central impervious core of a zoned embankment type dam is clay mixed with fine sand

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78. Seepage through embankments in an earthen dam is controlled by

drain trenches

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79. Seepage through foundation in an earthen dam is controlled by providing

impervious cut off

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80. The flow of water after spilling over the weir crest in chute spillway and side

channel spillway respectively are at right angle and parallel to weir crest