Geotechnical Engineering

DHARM

CAISSONS AND WELL FOUNDATIONS 795

m¢P m¢P

Scour level

D

F

w MB

(a) Elevation

p

H

(D–z)q z

q

sx

(c) Deflection profile (d) Pressure

distribution on sides

xc

B

(b) Plan

x

q

(e) Deflection at base (f) Pressure distribution at base

C

(x + x)c

q

Fig. 19.18 I.R.C. Method–key figure

The horizontal soil reaction at that level is given by

σx = K z

D

H.(Dz−θ)

or σx = mK

z

D

..( )v Dz−θ ...(Eq. 19.39)

wherem =

K

K

H

v

.

Total horizontal soil reaction P, acting on the sides is given by

P = Ldzx

D

..σ

z 0

= LmK z D Dv z dz

D

z (/ )(− ).θ

0

=

mK L

D

...v θ D^3

6

F

HG

I

KJ

or P =

2 mK

D

v Iv

θ

. ...(Eq. 19.40)

where Iv =

LD^3

12

, or the second moment of the area about the axis passing through the centroid

of the vertical projected area.