Question

Hydrogeology

1. You are given the following data set from a falling head slug test. You are asked to determine the hydraulic conductivity of the aquifer using Hvorslev's method. Assume that the diameter of the well is 7.6 cm, the length of the screen is 98 cm and there is no gravel pack around the screen. Time (sec) head (m) h/ho 0.56 0.457 0.392 0.345 0.308 0.28 0.252 0.224 0.205 0.187 0.168 0.149 0.14 0.131 0.112 0.108 0.093 0.089 0.082 0.075 0.071 0.065 1.000 0.816 0.700 0.616 0.550 0.500 0.450 0.400 0.366 0.334 0.300 0.266 0.250 0.234 0.200 0.193 0.166 0.159 0.146 0.134 0.127 0.116 18 21 24 27 30 36 39 42 45 48 51 54 57 60 63

Answer 1

Solution:

In Horslev's Method:

hydraulic conductivity= k= r² * ln( h/h0) / F* T_L

null

r= radius of screen

L=screen length

F=constant

This equation can be approximated by field data as

K = r² *ln ( L/r) / 2*L* T_L

T_L = time lag value corresponding to the value h / h0 = 0.37

from the table h/h0 = 0.366 for t=24 = T_L

ths, putting the values in the above equation:

K= (7.6/2)² * ln( 98*2/ 7.6) / 2 * 98 * 24

=9.976 * 10^-3 cm/s