Contents preface (VII) introduction 1—37

Downstream pile:

d = 255 – 248 = 7.0 m and b = 36.5 m

∴

α =

36.5

7.0 = 5.21

Using Eqs. (9.55), (9.51) and (9.52),

λ =

1 L

1 + α

2

O

1 L

2

O

2

M1 +

P ^=

M1 + 1 + (5.21)

P = 3.15

N

− 1 F λ −

Q

2 N

−1F

1.15 I

Q

1

2 I

1

∴

φE =

cos

G

J =

cos

G

J = 0.3810 = 38.10%

π

λ

π

H

K

H

3.15K

1

− 1 F λ −

1 I

1

−1F

2.15I

∴

φD =

cos

G

J =

cos

G

J = 0.2609 = 26.09%

π

λ

π

H

K

H

3.15K

Using Fig. 9.23 with

1

=

d

=

7.0

= 0.192,

b

36.5

α

φE = 38%

and

φD = 26%

Using the values of φD and φE obtained from Eqs. (9.51) and (9.52),

Thickness correction for φ

=

^38.1 ^− ^26.09 × 12. = 2.06% (–)

E

7

Correction for interference of intermediate pile (for φE)

= 19

(253.8 − 248)

× (5.8 + 5.8)

15

36.5

= 3.75% (–)

φ_E (corrected) = 38.1 – 2.06 – 3.75 = 32.29%
Based on the above calculations, subsoil hydraulic gradient line has been plotted in Fig.
9.26
Exit Gradient:

α =	36.5	= 5.21 ; H = 260 – 255 = 5.0 m
7.0
λ =	1 +	1 + α^2	= 3.15
	2