Question

A well is to be constructed in a fine sandy sub-soil formation. The discharge of the well under the depression head of 4 m is 0.004 m^3/sec. Calculate the diameter of the well.

(a) 2 m

(b) 2.5 m

(c) 3 m

(d) 3.5 m

This question was posed to me by my college director while I was bunking the class.

This key question is from Open Well and Dug Well topic in section Ground Water for Irrigation through Wells and Tubewells of Irrigation Engineering

Answer 1

Right answer is (c) 3 m

Best explanation: Given, Yield of well = 0.004 x 3600 = 14.4 m^3/hour

Q or yield = K x H

14.4 = K x 4 or K = 3.6 m^3/hour under head of 1 meter.

From Marriot’s table, the value of K/A for sandy sub-soil formation = 0.5

3.6/A = 0.5 or A = 7.2 m^2

Diameter of well = (A x 4/3.14)^1/2 = 3.07 m.