Civil Engineering Reference
In-Depth Information
Resisting moment, M
R
Due to base
30 0 1 5
.
.
45 0
.
kNm
=
×
=
Due to stem
=
46 0 0 7
.
×
.
=
32 2
.
kNm
Due to soil on heel
=
194 9 1 95
.
×
.
=
380 1
.
kNm
M
R
=
45 0
.
+
32 2
.
+
380 1
.
=
457 3
.
kNm
457 3
119 1
.
.
Factor of safety against overturning F
o
,
=
=
3 8
.
Bearing capacity:
Consider moments about point A.
If R
v
acts at a distance x from A, then
R x
v
=
457 3 119 1
.
−
.
=
338 2
.
kNm
that is
338 2
270 9
.
.
x
=
=
1 25
.
m within middle third of base
(
)
3
2
Eccentricity of R e
v
,
= −
1 25
.
=
0 25
.
m
R
B
6
e
B
=
270 9
3
.
6 0
×
.
25
=
v
Maximum bearing pressure
=
1
+
1
+
135 5
.
kPa
3
Factor of safety against bearing capacity failure F,
=
250
135 5
=
1 85
.
.
(b) Eurocode 7
For the overall stability of the wall, once again we check safety against the GEO limit state.
1.
Combination 1 (partial factor sets A1
+
M1
+
R1)
.
.
(i) Design material properties
1
1
−
+
sin
sin
φ
φ
′
=
d
φ
38
º:
Using Rankine s theory K
'
,
=
=
0 238
.
.
d
a
d
(ii) Design actions
In sliding and overturning, the weight of the wall is a permanent, favourable action. The
influence of the surcharge on the soil on the heel is ignored since transient (variable)
actions can never be considered favourable.
Stem G
:
0 4 4 6
.
.
1 84 25 1 0
.
.
46 0
.
kN
=
×
×
γ
×
γ
=
× ×
=
stem d
;
concrete
G fav
;
Base G
:
=
0 4 3 0
.
×
.
×
γ
×
γ
=
1 2 25 1 0
.
× ×
.
=
30 0
.
kN
base d
;
concrete
G fav
;
Soil on heel G
:
=
2 1 4 6
.
×
.
× ×
γ γ
=
9 66 18 1 0
.
× ×
.
=
173 9
.
kN
heel d
;
G fav
;
Total R
,
;
249 9
:
.
kN
v d
The thrust from the active earth pressure is a permanent, unfavourable action.
1
2
P
= ×
0 238 18 5
.
× × ×
2
γ
=
72 3
.
kN
a d
;
G unfav
;
