Geotechnical Engineering

DHARM

LATERAL EARTH PRESSURE AND STABILITY OF RETAINING WALLS 515

Depth, H = 3 m

γ

φ

=

=°

U

V

W

20 kN / m^3 for sand fill with level surface.

35

Limiting values of lateral earth pressure:

Active pressure = Ka.γH =

135

135

−°20 3

+°

sin ××

sin

= 0.271 × 60

= 16.26 kN/m^2

Passive pressure = Kp. γH =

135

135

+°20 3

−°

sin ××

sin

= 3.690 × 60

= 221.4 kN/m^2

Total active thrust per metre run of the wall

Pa =

1

2

16 26

1

2

γHK^2 a=××. 3 = 24.39 kN

Total passive resistance per metre run of the wall

Pp =

1

2

221 4^1

2

γHK^2 ..p=×× (^3) = 332.1 kN
Example 13.3: A gravity retaining wall retains 12 m of a backfill, γ = 17.7 kN/m^3 φ = 25° with
a uniform horizontal surface. Assume the wall interface to be vertical, determine the magni-
tude and point of application of the total active pressure. If the water table is a height of 6 m,
how far do the magnitude and the point of application of active pressure changed?
(S.V.U.—Four-year B.Tech—Oct., 1982)
58.9
43.124.4
6m 43.1 kN/m^2
6m Pa Pa
4m 3.62 m
Wall
(a)
86.2
(b) (c)
Fig. 13.53 Retaining wall and pressure distribution (Ex. 13.3)
(a) Dry cohesionless fill:
H = 12 m φ = 25° γ = 17.7 kN/m^3
∴ Ka =
125
125
−°0 406
+°
sin =
sin
.