Geotechnical Engineering

DHARM

534 GEOTECHNICAL ENGINEERING

φ = 30° Ka =

130

130

−° 13

+°

sin =

sin

/

Horizontal pressure of soil at 3 m depth = Kaγ 1 H 1 =^1

3

××16 3 = 16 kN/m^2

Lateral earth pressure at 6 m depth = Ka(γ 1 H 1 + γ 2 H 2 )

=

1

3

()16 3 18 3×+ × = 34 kN / m^2

Total active thrust per metre run of the wall,

Pa =

1

2

3163161

2

×× +× + ×× = + + (^318244827) = 99 kN
1.5 m
6
Wall m
g= 23 kN/m^3
Pa
R
To e x
2m 1.5 m
Heel 16 18
16 m
1.97 m
P = 99 kN/ma
3m
3m g= 16 kN/m^3
1.317 m W g= 18 kN/m^3
Fig. 13.71 Retaining wall (Ex. 13.26)
Let z metres be the height of the point of action above its base.
By taking moments about the base, z =
(.)24 4 48 1 5 27 1
99
×+×+×
= 1.97 m
Weight of wall per metre run, W = 6 × 1.5 × 23 +
1
2 × 2 × 6 × 23
= 207 + 138 = 345 kN
Let the distance of its point of action from the vertical face be x m.
By moments, x =
207 0 75 138
13
6
345
1 317
F ×+×
HG
I
KJ=
.
.m
Let x metres be the distance from the line of action of W to the point where the resultant
strikes the base.
x P
W
a
197.
= ∴ x =
197 99
345
0 565
.
.
×
= m