Question

Bored tube wells in rocky consolidated formations as are encountered in the South Indian States of our country are usually drilled by _____________

(a) rotary drilling rigs

(b) percussion drilling rigs

(c) down the hole hammer (DTH) rigs

(d) cable method of drilling

The question was posed to me in an online interview.

The above asked question is from Tube Well-1 in division Ground Water for Irrigation through Wells and Tubewells of Irrigation Engineering

Answer 1

The correct option is (c) down the hole hammer (DTH) rigs

The best explanation: In rocky areas, down the hole hammer rigs (DTH rigs) are used to drill isolated holes of 10 to 15 cm in diameter. They are usually in the depth range of 100 m and mostly been constructed in southern states of India. This type of wells usually depends on joints and fissures in the rocks for their water supply.