Question

The radius of the well curb should be kept _________ larger than the outside radius of well steining.

(a) 2 cm and 4 cm

(b) 2 m

(c) All of the mentioned

(d) None of the mentioned

This question was addressed to me in a national level competition.

Origin of the question is Well Sinking topic in portion Well Foundations of Geotechnical Engineering II

Answer 1

Right choice is (a) 2 cm and 4 cm

For explanation I would say: As a precaution to avoid tilts and shifts, the radius of curb should be kept 2 to 4 cm larger than the outside radius of well steining.