Q

2ttT

where Ko(r/A) = modified Bessel function of zero order and second kind, and A = Tc as defined before. The values of Ko(r/A) versus r/A are shown in Table 9.8.1. The value T can be determined as in a confined aquifer with the use of the matching procedure. The data curve is obtained from a plot of s versus r on log-log paper, and the type curve is obtained from a plot of Ko(r/A) versus r/A. Overlapping these two plots matches the two curves, and four coordinates of an arbitrary selected print on the matching curve are noted. The value T is then calculated from Equation 9.8(29) as

The resistance c can be determined from c = A2/T when T and the values of r and r/A of the matching point are substituted into this equation.

Hantush Method

Equation 9.3(19) shows that when r/A << 1, the drawdown can be approximated by

2vl r

TABLE 9.8.1 VALUES OF THE FUNCTIONS K0(X) AND EXP (X)K0(X)

x

K0(x)

exp (x)K0(x)

x

K0(x)

exp (x)K0(x)

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