57. The R.L. of ground water table on the sides of a valley is 1505 m whereas R.L. of the stream water is 1475 m. If 60? slope consists of pervious soil between R.L. 1485 m to 1500 m, the gravity spring may be expected at the point of reduced level
A. 1500 m
B. 1505 m
C. 1475 m
D. 1485 in.
58. Pick up the incorrect statement from the following :
A. An impervious layer a few metres below the water table in the sub-soil, is generally called Mota layer
B. Mota layer is very useful to give structural support to open deep wells
C. A bore hole is generally provided in the mota layer for deep wells
D. Shallow wells a..e always of less depth as compared to deep wells '
59. Pick up the correct statement from thefolTowing :
A. The water level in a stilrw? ell, represents the ground water table level
B. The difference between water table level and the water level in a well after pumping, is called depression head
C. The surface of water table surrounding a well during pumping, forms a cone of depression
D. All the above.
60. While determining the yield of open wells by the pumping test
A. velocity of recharging water, increases with depression head
B. depression head resulting at critical velocity, is called critical depression head
C. working head is generally limited to ?1 rd of the critical depression head
D. maximum safe yield of an open ell, is expected at critical depression head.
61. Specific capacity or yield of wells, is generally ex-pressed, as
A. m3 per sec
62. The expected discharge to be obtained from an open well sunk in coarse sand is 0.0059 cumec. If the working depression head of the well is 3 m, the minimum diameter of the well, is
A. 2 m
B. 2.25 m
C. 2.50 m
D. 3.00 m.
63. The water level in an open well was depressed by pumping 2.5 m and recuperated 2.87 m in 3 hours and 50 minutes. The yield of the well per minute is
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